6. site 392: south rim of blake nose - deep sea drilling · 2007. 5. 10. · site 392, situated on...

6. SITE 392: SOUTH RIM OF BLAKE NOSE

Shipboard Scientific Party1

SITE DATA

Dates Occupied: 23-28 September 1975

Position: 29°54.63'N; 76°10.68'W

Water Depth: 2601.0 meters (corrected PDR), 2606.5 meters(drill pipe)

Penetration: 349 meters

Number of Holes: 2

Number of Cores: 35

Total Length of Cored Section: 295.0 meters

Total Core Recovered: 37.9 meters

Percentage Core Recovered: 12.8 per cent

Oldest Sediment Cored: Neocomian or older recrystallizedskeletal limestone at 349 meters sub-bottom.

Basement: Not reached

Principal results: We drilled two holes at Site 392; Hole 392 wasabandoned when the bit encountered hard limestone at 48meters — too shallow to adequately seat the bottom-holeassembly. We successfully spudded in Hole 392A, 1500 feet tothe northwest. Coring began at 50.5 meters sub-bottom in palebrown ooze and continued in mostly soft sediment to 99 meterswhere hard "reef" limestone was encountered. The hard"reef" limestone was cored continuously until the bit wasdestroyed at 349 meters sub-bottom.

The sedimentary sequence at Site 392 is essentially the sameas that at Site 390. The Campanian/Albian unconformitypresent at Site 390 is also present at Site 392 indicating itspersistence along the edge of the Blake Nose. UpperCampanian ooze directly overlies Aptian-Albian ooze and thelower half of the Upper Cretaceous is missing. A thin intervalof Barremian ooze overlies hard shallow-water limestone. Thetop of the limestone is brecciated, stained and cemented withlimonite, and contains limonite ooids. Below this the limestoneis of the three general types: (1) fenestral limestone, (2) oolite,and (3) a skeletal moldic limestone. Fossils are allshallow-water types. All the limestone has been recrystallizedand some of the diagenesis must have occurred above the watertable.

Shallow-water limestone accreted during the EalryCretaceous, but accumulation ceased by late Neocomian orcertainly by early Barremian time, after which accretion did notkeep pace with subsidence and only pelagic oozesaccumulated.

'William E. Benson and Robert E. Sheridan, Chief Scientists; PaulEnos, Tom Freeman, Felix M. Gradstein, Ivar O. Murdmaa, LéoPastouret, Ronald R. Schmidt, Daniel H. Stuermer, Fred M. Weaver,Paula Worstell.

BACKGROUND AND OBJECTIVES

Background

Site 392, situated on the southeastern lip of the BlakeNose (Figures 1 and 2) was drilled to supplement ourinformation about Cretaceous limestones drilled at Sites 389and 390.

Cretaceous reefs and related structures form a chain thatcircles the Gulf of Mexico, extends through Cuba and theBahamas, and rims the escarpment of the Blake Plateau(Figure 3, Site 390, after Paulus, 1972, and Meyerhoff andHatten, 1974). Seismic reflection data have suggested thatthis reef and bank-rim complex extended from CapeHatteras to off the coast of New Jersey and along the edge ofthe Georges Bank (Sheridan, 1974; Schlee et al., 1976).

In Mexico the Cretaceous reef complex rimspetroleum-bearing limestone platforms (Golden Lane Atoll,Enos, 1974) and in Texas it is recognized as a zone ofstratigraphic traps (Edwards Limestone, or Stuart Cityreef). Despite its economic importance in the Gulf area,the age and structure of the reef complex along the Atlanticcontinental margin are poorly known and the time the reefcomplex ceased to build and subsequently sank is poorlydocumented. Piston core and dredging data along the BlakeEscarpment indicate that a complex reef-lagoon faciesexisted from at least Neocomian to Cenomanian orCampanian time (Heezen and Sheridan, 1966; Sheridan etal., 1971) and drilling at Site 390 showed that the carbonateshelf was built during Barremian time at that site.

Objectives

The primary objective of this site was to drill into themassive part of the Blake Nose reef bank-rim complex andto study the makeup of this facies (Figure 4). We alsoplanned to tie Site 392 into the geologic profile interpretedfrom Site 390 drilling to test the interpretation and give amore definitive picture of Blake Nose reef structure.

OPERATIONS

We approached Site 392 from the southeast andconducted a seismic survey along a course of 300° —following a track similar to that approaching Sites 389 and390 (Figures 5 and 6). We selected the location for Site 392on the prominent reef-like structure near the south edge ofthe Blake Nose. A 16-kHz beacon was dropped at 0605hours2 23 September 1975 where 100 meters of overlyingsediment (0.1 sec) appeared sufficient cover to seat the bit.Glomar Challenger continued on course to record the

2Time in text is local time.

337

SITE 392

80° 75° 70° 65°

Figure 1. Map showing location of Site 392 relative to the Atlantic margin.

60°W

sedimentary reflectors northwest of the structure so that wecould correlate them with those reaching Site 390.

As shown on Site 389 profile (Figure 7), the Site 392seismic profile (Figure 8) shows that the reef was drapedwith beds dipping northwest into the nose but clearlytruncated by erosion along the Blake Escarpment. Thistruncation on the southeast precluded entrapment of anypetroleum so that we could drill the site without danger ofpollution.

We returned the Challenger to the beacon, loweredhydrophones, and began automatic positioning by 0745hours. Several hours were required to center over thebeacon because of 35-kt winds and 10-15 foot swellscoming from the southwest. The water depth is 2605 meterscorrected (1424 fm corrected, 1386 fm uncorrected). Thepipe was run in at 1130 hours and bottom was felt at 2609.5meters — a little shallower than anticipated suggestingsome local relief on the bottom. Following a delay to repairthe Bo wen power sub and recover the ship's position, wespudded in at 2030 hours and washed down to 47.5 meters.

Soft but firm sediments were encountered to only 42meters sub-bottom where the bit hit hard limestone andrubble rock. Our estimate of soft sediment overburden wasincorrect or the beacon had reached bottom a little south ofthe drop point. Nevertheless the sediment cover wasinsufficient to seat the bit. Consequently, we pulled pipe

above mud line at 0100 on 24 September 1975, and offset1500 feet northwest (Figure 6), where our profile showedmuch thicker sediments.

Hole 3 92A was spudded in at 0440 hours at a differentwater depth of 2601 meters corrected (1422 fm corrected,1384 fm uncorrected). Felt depth was 2606.5 meters. Herethe hard limestone of the reef complex was reached at 89 to98 meters sub-bottom — deep enough so that the bit couldbe sufficiently weighted and torqued to continuously drillthe hard limestone.

We continuously cored the hard limestone to asub-bottom depth of 349 meters. Penetration was extremelyslow (about 120+ minutes per core) and recovery was verypoor, comprising, at times, no more than a few fragments ofhard limestone in the core catcher.

The poor recovery apparently was not caused by technicalmalfunction. The bit neither jammed nor clogged and theseating of the inner core barrel was normal. The limestoneitself was simply very difficult to drill. The limestone isrecrystallized, and very brittle, and has healed sheetingjoints parallel to bedding. Presumably, the weight of the bitcracked this brittle limestone along the horizontal planesand 3-8 cm thick fragments were rolled around between thecones of the bit, instead of moving easily into the corebarrel. The result was recovery of a number of lens-shapedlimestone discs in the bottom of the core barrel. Cores 27

338

SITE 392

30°

75° 70°

Figure 2. Detailed bathymetry in the vicinity of Sites 389, 390 and 392. Depths in fathoms are on the basis of computationsofE. Schneider (pers. commj. Profile along track E is shown in Figure 3.

and 28 at 288 and 297.5 meters sub-bottom, respectively,were cut comparatively rapidly, 35-60 min/core, and werecovered some cavernous limestone fragments. Apparentlya limestone cavern of at least 10 meters depth waspenetrated.

We cored continuously until 1630 hours 27 September,when, because of extremely slow drilling rates, inability torecover material, and time constraints, we terminated Hole392A at a depth of 349 meters.

The tools were on deck by 0230 hours 28 September andChallenger left Site 392 bound for port. The bit had beendrilled to destruction. Although less than 250 meters of hardlimestone was penetrated two cones were gone and the othertwo had no bearings and were held in place only by bent and

twisted cone guides. Nearly 90 per cent of the tungstenbuttons had been plucked from the remaining cones.

Drilling in Hole 392A penetrated 349 meters of soft oozeand hard limestone. The hole terminated in Barremian orolder limestone. We recovered two cores from Hole 392 andattempted 33 cores in Hole 392A. Drilling results are givenin Table 1.

LITHOLOGY

Our objectives in drilling Site 392 were to examine thenature of the prominent shelf-edge reflector (' 'reef') shownby seismic profiling of the Blake Nose. Hole 392, drilled onthe approximate topographic crest, penetratedmanganiferous sediments and carbonate ooze before

339

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p SFCONüs , S.

r T — r . , , NEAR SITE 390

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8 ' I ! I ! "8, 1,0 15 Op 0,1 // 09 : 15 | SO I. CO

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14 APRI1 " •'. , i i i I ' - I

Figure 3. Vema 26 single-channel reflection across the Blake Nose along track E shown in Figure 5. (Data supplied by Lamont-Doherty Geological Observatory.)

SITE 392

NWSE

Site392

. | | |

-! o

J -5 .0

I

Figure 4. Geologic cross-section across Blake Nose "reef" interpreted on basis of Challenger profile shown on right. Localtimes are used.

30 10'

30°00'

DR1158

[

C

:SN me D1 :s

• DR1100

\

G>DR 1012

\ s N 0952

SN0554S ;

SN 1304

DR 06500

Å-op beacon'i50 29 Aug. 75:e390

\vDR090

8 Aug. 75

Drop beacon1314 28 Aug. 75Site 389

\ 1314

/ % DR 1330

\Satellitefix Site 389

IESN 0802

6

— ©DR 1408

76° 10' 76 W

Figure 5. Track of Glomar Challenger during survey madeprior to drilling Site 389. Local times are used.

entering lithified limestone at 48 meters sub-bottom. Twocores of limestone were recovered from this hole before wemoved 460 meters westward, down the dip of the reflector,to spud into a thicker sediment cover. We continuouslycored Hole 3 92A which penetrated 90 meters of ooze and259 meters of hard limestone to the termination of the hole

Figure 6. Track of Glomar Challenger on approach to Site392. Local times are used.

at 349 meters sub-bottom. Recovery was poor (9%) andcores comprised mostly rounded pieces of limestone whichalthough probably in proper stratigraphic sequence are notcontiguous.

Lithologic Units

We recognized four lithologic units (Table 2, Figure 9).The youngest is ooze and clay representing a condensedCampanian to Barremian section. The underlying threeunits are limestone — possibly Neocomian in age, but notyet satisfactorily dated. The principal components in the

341

SITE 392

NW/WSE

390389

- 3

- 5

&FF

i1100 1200

I1300

0900- 6

10

1000 km

Figure 7. Seismic reflection profile made by Glomar Challenger prior to drilling Site 389 showing location of Site 392. Localtimes are used.

major and minor lithologies of Hole 391A are shown inFigure 10.

Unit 1 — Nannofossil Ooze and Clay (0-99.3 m)

Unit 1 is dominantly nannofossil ooze with tworecognizable nannofossil clay intervals and possibly otherswhich were mixed by drilling. The unit extends to 99.3meters sub-bottom in Hole 392A, but the interval above 50meters was not cored.

The nannofossil ooze is soft and white (10YR 8/2) to paleolive (5Y 6/3). The basal 1 meter of Core 392A-3 (about 88m) is slightly firmer and more colorful, brownish yellow(10YR 6/6), with a thin (<5 cm) reddish yellow (5YR 6/6)and yellow (10YR 7/6) zone. Planktonic foraminifers formup to 20 per cent of the sediment in the upper part of the unit(Core 392A-1). A small terrigenous component, quartz,feldspar, clay, and mica, is present; siliceous skeletons areabsent (Table 3). Total calcium carbonate content is 89 percent in the upper part of the unit (Core 392A-1) and 60 percent in the lower part (Appendix I, this volume).

Cores 392A-2-1 and -3-1 contain dark gray (10YR 4/1)and greenish gray (5G 4/1) nannofossil clay with about 9 percent quartz silt. The proportions of constituent particles arethe same as in the light-colored oozes except that calciumcarbonate, dominantly nannofossils, is reduced to about 40per cent.

Two pieces (totaling 8 cm) of moderately well lithifiedforaminifer nannofossil ooze occur at 81 meters sub-bottom

(Section 392A-3-2). A second limestone, light brown topink (10YR 5/3, 10YR 6/4, 5YR 7/4), forms two layerstotaling 35 cm near the base of unit 1 (Core 392A-4). Thelimestone is composed primarily of large undistortedammonites closely packed in a matrix of lime mud andplanktonic foraminifers.

The contact between unit 1 and the underlying fenestrallimestone is at 99.3 meters sub-bottom (in Section392A-5-1). The base of unit 1 is marked by a thinred-stained interval of limestone clasts, skeletal rubble,laminated crusts, and reddish brown ooids. This zoneoccurs in both Holes 392 and 392A, but at depths differingby 40 meters (subsea and sub-bottom, Cores 392-1,392A-4, CC and 392A-5). Multiple crusts of lustrous, darkreddish-brown, laminated calcareous material laced througha matrix of dense light gray carbonate, dark brown ooids,and skeletal debris. The skeletal debris includes belemnites,green algae, and a variety of corals. The reddish brownooids are concentrically laminated oblate spheroids 0.2 to 3mm in maximum diameter with spherical to irregular nucleiconsisting of earthy, rusty particles (limonite?) or, rarely, ofseveral smaller ooids. The ooids are presumed to be rich iniron. Individual ooids are generally not in contact with eachother, although a few areas show contact with possiblefitting of slightly polygonal ooids. Major axial planes ofadjacent ooids are roughly parallel, but not everywherehorizontal. The ooids form wavy bands that pass not onlythrough the matrix and laminated crusts, but also through

342

SITE 392

Site392

y

o

-4 .0

—5.0

-6.0

• . . - . .

-7.0

0500 0530 0600

5 km

Figure 8. Glomar Challenger single-channel reflection pro-file across Site 392. Local times are used.

limestone clasts. The clasts consist of skeletal limestone,containing a probable rudist fragment and muddy limestonestained uniformly dark red. Pebbles totaling about 5 cmwere recovered in Core 390-1 and a total of 13 cm wasrecovered from contiguous Cores 392A-4 and -5 whichwere continuous, but had only 6 and 18 per cent recovery,respectively.

The remaining three units (2-4) are well-lithifiedlimestones apparently closely related in time, space, andgenesis. The lithologic types are interbedded and somewhat

intergradational in constituent components, although the"end members" are readily distinguished by sedimentarystructures and diagenetic features.

Unit 2 — Fenestral Limestone (99.3-212.8 m)

Beneath the surficial crust of unit 1, unit 2 ischaracterized primarily by its distinctive sedimentarystructures, especially disrupted lamination and "fenestral"pores. The unit extends from 99.3 meters to the top of theoolitic limestone of unit 3 (213 m sub-bottom). Thelimestone is uniformly light in color, mainly very palebrown (10YR 8/3 to 7/4). The constituent particles arepelletoids, intraclasts (both predominantly soft at the time ofdeposition), lime mud, and a few fossils. The fossils includemiliolids, other small benthic foraminifers, high-spiredgastropods, and very thin-shelled pelecypods, The biota ismore varied lower in the section with the presence of greenalgae (about 160 m sub-bottom) and coral fragments (195m).

Much of the rock is poorly laminated muddy layersinterspersed with thin (mm) laminae and lenses ofcommonly micrograded grainy carbonate and with layers ofcoarse intraclasts. The laminae are warped and disrupted toproduce fenestral pores or a "birds-eye" texture (voidselongate parallel to stratification). This type of pore may beformed by desiccation, accumulation of gases beneathcohesive mud layers, and/or algal growth. Mud cracks withpolygonal patterns presumed to be formed by desiccationare fairly common on bedding structures. Desiccationprobably also accounts for a local "crumb" texture ofmuddy carbonate and may have produced many of theintraclasts virtually in situ. Other pores consist of vertical orarcuate strings of bubble-like cavities joined by cracks ornarrow tubes. The "bubbles" are less than a millimeter indiameter and the strings seen in the cores are severalcentimeters long. Strings are probably much longer andextend beyond the dimensions of the core. The bubblestrings may be burrows with a series of connected galleriesor they could record the difficult passage of gas throughcohesive sediment. Some of these syndepositional poreswere evidently enlarged by solution. Fenestral and visibleintergranular pore space commonly exceeded 40 per cent ofthe bulk volume,but virtually all pore space has been filledduring a complex diagenetic history. The remainingporosity of the rock is less than 5 per cent, largely inspar-lined vugs.

Although unit 2 is nearly homogeneous, it contains a fewinterbeds of finely crystalline limestone characteristic ofunit 4. The disappearance of fenestral fabric coincides withthe top of an interval in which coated grains are prominent.This transition, at 212.8 meters marks the contact betweenunits 2 and 3 (Figure 9).

Unit 3 — Oolite (212.8-241.6 m)

Pale brown oolite (10YR 7/3) with numerous intraclasts,skeletal fragments, varied fossils, and little mud comprisesunit 3. The unit is 29 meters thick and extends to the abruptdisappearance of oolite as a dominant lithology at 241.6meters. Near the top of the unit the ooids range from thinsurficial rims to thick asymmetric coatings, possibly algal.

343

SITE 392

Core

Hole 3921

2Total

Hole 392A1

23

4

56789

101 112131415161718192021222324252627282930313233

Total

Cored

Total Depth(m)

2658.0-2666.5

2666.5-2669.52669.5

2657.0-2666.5

2672.5-2676.02685.5-2695.0

2695.0-2704.5

2704.5-2714.02714.0-2723.52723.5-2733.02733.0-2742.52742.5-2745.52745.5-2752.02752.0-2761.52761.5-2771.02771.0-2780.52780.5-2782.52782.5-2790.02790.0-2799.52799.5-2809.02809.0-2818.52818.5-2828.02828.0-2837.52837.5-2847.02847.0-2856.52856.5-2866.02866.0-2875.52875.5-2885.02885.0-2894.52894.5-2904.02904.0-2913.52913.5-2923.02923.0-2932.52932.5-2942.02942.0-2951.52951.5-2955.5

2955.5

Interval

Sub-Bottom Depth(m)

47.5-57.0

57.0-60.060.0

50.5-60.0

66.0-69.579.0-88.5

88.5-98.0

98.0-107.5107.5-117.0117.0-126.5126.5-136.0136.0-139.0139.0-145.5145.5-155.0155.0-164.5164.5-174.0174.0-176.0176.0-183.5183.5-193.0193.0-202.5202.5-212.0212.0-221.5221.5-231.0231.0-240.5240.5-250.0250.0-259.5259.5-269.0269.0-278.5278.5-288.0288.0-297.5297.5-307.0307.0-316.5316.5-326.0326.0-335.5335.5-345.0345.0-349.0

349.0

Cored(m)

9.5

3.012.5

9.5

3.59.5

9.5

9.59.59.59.53.06.59.59.59.52.07.59.59.59.59.59.59.59.59.59.59.59.59.59.59.59.59.59.54.0

283.0

TABLECoring Summary

Recoverec

(m)

0.2

3.03.2

2.7

3.53.5

0.6

1.70.90.20.21.51.60.950.10.050.10.30.71.00.10.80.90.70.70.70.20.20.60.10.40.10.10.20.00.0

25.3

(%)

2

10026

28

10037

6

18922

502510

10.547

1147

1177722614112009

1, Site 392

Lithology

Mn module and limestonefragmentsLimestone

Nannofossil and foraminifer

oozeMarly nannofossil oozeNannofossil ooze with lime-stone fragmentsNannofossil ooze andlimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestone

5 LimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestoneLimestone--

Time-RockUnit

(Indeterminate)

Quaternary

Upper Campanian

Middle-Upper AlbianLower-Middle Albian; Upper Aptian

Barremian

(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)(Indeterminate)--

TABLE 2Summary of Lithologic Units, Site 392

Unit LithologyTime-Rock

UnitApparent Thickness

(m)Sub-Bottom Depth

at Top(m)Recovered

Cores

Nannofossil and foraninifer ooze^lightcolored and dark gray marly nannofossilooze

Fenestral limestone, pale brown, intra-clasts, foraminifers, mollusks, laminae,mud cracks, burrows, fenestral pores

3 Oolite, intraclasts, fossils, laminated4 Skelmoldic limestone, light gray, fossils,

pelletoids, finely crystalline, moldicporosity

Total limestone recoveredTotal penetration

Campanian, Albian, UpperAptian, Barremian

Indeterminate

Indeterminate

Indeterminate

>48.8

113.5

<50.5

99.3

28.8107.4

25.3m349m

212.8241.6

-20 392A-1 to 5-1, 130 cm

8.9 392A-5-1, 130 cm through 19-1

8.7 392A-19-2 through -22-1, 120 cm

2.7 392A-22-1, 120 cm through-31(No recovery 32 qnd 33)

344

SITE 392

NOT CORED

90.1-

150-1

200-

212.8-

NANNOFOSSILOOZE,light color; foraminifersNANNOFOSSILCLAY,dark color

LIMESTONE RUBBLE00IDS, red stain

FENESTRALLIMESTONE;pale brown, withintraclasts, foraminifers,mollusks, laminae,mudcracks, burrows, andfenestral pores

UNIT 1

UNCONFORMITY

UNIT2

Finely crystalline limestone Fenestral pore

OLithoclast

©Ooid

Nannofossil ooze Oolitic crust

OOLITE; withintraclasts, fossils,and laminae UNIT3

SKELMODIC LIMESTONE;light gray, finely crystalline;fossils, pelletoids

UNIT4

T. D. = 349 m

Figure 9. Summary oflithologic units, Site 392.

Toward the base, ooids with multiple concentric coatingspredominate. Broken ooids are prominent at the base of theunit (240 m). Identifiable fossils are not abundant, but arepresent throughout. Fossils include green algae, smallbenthic foraminifers, robust clams, a few coral fragments,an encrusting bryozoan, and a cemented burrow lining, inaddition to the omnipresent miliolids and gastropods. Animportant element is a codiacean green algae (Figure 11),abundant in several layers.

Sedimentary structures include lamination and alternatingcoarse-fine layering; we did not detect inclined lamination.

Small-scale erosional scour is common; somepenecontemporaneous cementation is indicated by grainsthat were truncated by the erosion surface. Cemented ooliteintraclasts occur in unit 3 and near the base of overlying unit2.

Initial porosity of this sediment was high because of themud-free texture (30%-40% with normal packing) and theshelter pores provided by large intraclasts and fossils. Sheetcracks and small vugs were formed early in the diageneticsequence. Virtually all porosity has been occluded by acombination of diagenetic sediment and cement (Figure 12).In a few samples the diagenetic sediment consists of unevencoatings on grains, forming narrow "necks" connectinggrains (meniscus sediment). Pendants of early cement occuron the undersides of grains or the roofs of sheet cracks(Figure 12). Both meniscus sediment and pendant cementare indicative of pore occlusion in a two-fluid-phase system— air and water (i.e., the vadose zone). Previously knownexamples of meniscus sediment are restricted to Pleistoceneand younger rocks, and only two examples of pendantcement have been reported (by Freeman, from the Ordovianof Arkansas, and Purser, Jurassic of France).

Unit 3 is oolite throughout except for a few beds of finelycrystalline limestone like that of unit 4.

Unit 4 — Skelmoldic Limestone (241.6-335.5 m)

Limestone of unit 4 is characterized primarily bydiagenetic homogeneity that partially obscures depositionaltextures and composition. The texture of the white (10YR8/2) or very pale brown (10YR 8/3) limestone is finelycrystalline or "sucrosic," generally with skeletal molds.Solution-enlarged intergranular porosity and vugs are alsocommon. Despite some growth of spar in large vugs,present porosity ranges up to 40 per cent; 5 per cent iscommon. Sudden increases in drilling rate and drops of thedrill bit from 293 to 393 meters and from 322 to 326 metersindicates the presence of zones of cavernous porosity atleast 10 meters thick in the lower part of the intervalpenetrated. Large connected vugs in a piece of rock fromthe core-catcher sample at 296 meters support thisinterpretation.

The original lithology of unit 4 was probably somewhatvaried, although this is readily visible only near the top ofthe unit where diagenetic effects were less severe.Elsewhere it is largely obscured by the diagenetic overprint.The dominant components appear to have been hardpelletoids, miliolids, and gastropods with few intraclastsand little or no interstitial lime mud. The biota was variedalthough not lush. In addition to the dominant miliolids andgastropods, it includes dasyclad and codiacean green algae(Figure 11), small benthic foraminifers, pelecypods, andbranching corals(?). A cemented burrow lining is alsopresent. Gastropods and dasyclad algae are the usualvictims of skeletal mold formation.

Interbedded lithologies, indicated by recovery of isolatedpieces, are oolite and, rarely, fenestral limestone. Becauseof poor recovery little can be said about the stratigraphicsequence of unit 4.

Interpretation

We present a "simplest case" depositional cycle for Site392 followed by consideration of some secondarydiagenetic features.

345

SITE 392

HOLE392 A

SMEAR SLIDE SUMMARY

Figure 10. Estimate of major components in dominant and minor lithok>gies, Site 392.

Unit 1 represents pelagic accumulation with severalminor influxes of terrigenous material, dominantly clay.The apparent hiatus between Campanian and lower Albianseems to be within an uncored interval but the sedimentsabove and below are not appreciably different. Althoughintervals of dark nannofossil clay are confined to theAlbian-Barremian sediments, the predominant oozes ofthose stages are lithologically indistinguishable from thoseof the Campanian.

Although comparison with the age-equivalent sedimentsrecovered from Site 390, only 25 km away on the northernpart of the Blake Nose, is hampered by intermittent coringand drilling disturbances in some cores, some differencesare immediately obvious. The Barremian to Campaniansection is thicker at Site 392 (40 m vs. 24 m), although thetop of the Campanian was not cored here, and the entirepost-limestone section is only about half as thick (90 m vs.161 m). The distinctive variegated (brown, red, and white),firm marly nannofossil ooze which constitutes the entireBarremian through Albian section at Site 390 is not presentat all at Site 392. Conversely, the ammonite limestone is notpresent at Site 390. In view of the continental margin settingof the Blake Nose and of the complexities indicated byseismic stratigraphy between the two sites, some variation isprobable, although we would expect better local continuityof the pelagic or hemipelagic sediment (cf. suggestedcorrelations for western North Atlantic basin (Lancelot etal., 1972).

The origin of the red limestone rubble and the associatedgoethite ooids and crusts at the base of unit 1 were thesubject of debate onboard ship. The alternative hypotheseswere (1) soil formation upon subaerial exposure of theunderlying limestone and (2) formation by submarineweathering of an erosional surface without appreciablesediment accumulation during submergence, prior to theonset of pelagic sedimentation. The subaerial hypothesiswas favored on the basis of shipboard examination, but later

discovery of coccoliths within ooids, crusts, and alteredlithoclasts suggests a submarine origin of these features.

The fenestral limestone of unit 2 was probably depositedon a tidal flat. The features on which we base thisinterpretation are outlined in Table 4. Oolite sedimentation,unit 3, indicates deposition in shallow water, a high degreeof supersaturation relative to calcium carbonate (normallyaragonite), and highly agitated conditions. These conditionscommonly occur at shelf breaks where oceanic water isfocused into strong currents. We infer for unit four open orslightly restricted shelf depositional conditions because ofthe well-washed sediment, hardened pelletoids, andreasonably diverse, although not lush, biota. A modernanalog is the pelletoidal sand environment which coversvast areas of the Great Bahama Banks, including somewhatdeeper (> 10 m) bank margins where ooid shoals, reefs,and islands are lacking. Some degree of restriction might beinferred from the few muddy and fenestral limestoneintervals and from the lack of certain faunal elements (e.g.,large benthic foraminifers) common to open shelfcommunities.

The limestone units taken as a group could have beendeposited in a single sequence of regression or verticalaccretion relative to sea level (Figure 13). The accretionaryprocesses outlined could produce the elevated lip detectedseismically at the edge of the Blake Nose. In the final stagethe local area was emergent and caverns were developedsuch as those drilled in unit 4. At this time the entire250-meter limestone section cored at Site 392 was probablysubjected to the diagenetic effects of fresh-watercirculation, suggesting that the water table was some 6meters above sea level.3

3In rocks capable of maintaining a fresh-water lens, the ratio betweenelevation of the water table above sea level and depression of the fresh-water/salt-water beneath the lens (a function of the density contrast bet-ween the waters) is about 1:40.

346

SITE 392

TABLE 3Constituent Particle Composition of Unit 1 Average Percentages (standard deviation shown in parentheses),

Adjusted to Carbonate "Bomb" analyses

Lithology Clay Quartz Mica Carbonate Unspecified Nannofossils Foraminifers Siliceous Fossils

Nannofossil ooze(9 samples)

Clay and marlyooze

(4 samples)

12(9)

42

1(1)

10

1(1)

5

16(11)

7

65(12)

7

5(7)27

Clear microspar

Brown micrite

Centripetal spar

Horizontal sectionII. Further wetting by less turbid,

carbonate-saturated water producesmicro-stalactitic (pendant) fringeof cement.

IV. Final occulusion of intergranularpores by a combination of threecement morphologies (lumpedhere under a single mosaic habit).

Figure 11. Common fossils found at Site 392 (a) codiaciangreen algae cf. Cayeuxia, especially abundant in unit 3oolite; (b) dasyclad green algae is abundant as molds inunit 4, skelmoldic limestone.

Figure 12. Meniscus sediment and micro-stalagtitic (pen-dant) cement attests to periodic vadose conditions.

The model outlined does not require pre-existing relief atthe shelf edge. If relief is deemed necessary to account forsome restriction of circulation in unit 4 it could have beenprovided by a number of non-tectonic developments such as(1) a discontinuous reef barrier, (2) relief inherited from anearlier cycle of deposition (a modern example is thePleistocene eolianite ridges which rim the Bahama Banks),or (3) constructional topography from oolite shoals orshelf-margin skeletal sands. The coexistence of ooliteshoals during deposition of unit 4 is indicated by oolite

347

SITE 392

TABLE 4Sedimentary Features of Unit 2, Fenestral Limestone, Indicative of

Processes Active in Tidal Flat Sedimentation.

Feature Process

Lamination

Very thin micrograded laminae

Mud cracks

Crumb texture

Abundant soft intraclasts

Fenestral porosity

Impoverished fauna, low speciesdiversity

Periodic sedimentation, "punctuation"by algae mats

Periodic sedimentation by sheetflooding at high tide

Desiccation

Desiccation

Desiccation and sheet flooding

Desiccation, gas evolution, algal growth

Environmental stress: variablesalinity, desiccation, variablecurrents, periodic exposure

Note: The processes indicated are not the only possibilities, but are con-sistent with an overall interpretation of tidal sedimentation for unit 2.

intraclasts and oolite interbeds at Site 392. The presence ofreefs is suggested by coral fragments in units 2-4, but theyare very rare except in the red limestone rubble. Moreover,traces of rudists, the most common Lower Cretaceous reefbuilders, are virtually absent. The codiacean green algae(Figure 11) could conceivably have been reef formers, butthey are also prominent members of level-bottomcommunities.

An important second-order cycle is suggested by thecavernous porosity encountered in unit 4. The scale of thesefeatures requires extensive exposure to meteoric water. Thiscould have been accomplished by fresh-water circulation inat least the lower part of unit 4 before it was covered byyounger rocks. Thus the single cycle outlined in Figure 13may have begun following exposure of the basal part of unit4 (e.g., below 293 m sub-bottom). Poor recovery from unit4 precludes identity of any surface of subaerial exposure

FENESTRAL LIMESTONE

Figure 13. Detail of fades succession, Site 392. Coral-algal reef is inferred from traces inassociated rocks.

348

SITE 392

that might be related to early cavern formation, buterosional features interpreted as microkarst formation wererecovered in a rock from 265 meters sub-bottom. Noexposure surface is present at the contact between units 3and 4. In fact, the upper part of unit 4 has suffered lessdiagenetic overprint than lower portions, which would beconsistent with earlier exposure of the lower portion.

Periodic exposure may have occurred during depositionof the oolite. Erosional surfaces with truncated grains andthe occurrence of cemented oolite intraclasts point to earlycementation. The lack of biological erosion (e.g., borings)or encrustation associated with the erosion surfaces suggestssubaerial rather than submarine cementation. The formationof the meniscus and dripstone cements (Figure 12)probably required subaerial exposure.

Despite the regressive (upward shoaling) nature of thesedimentary cycle at Site 392, the net relative movement ofthe entire shelf during this period was probably downward.This is necessary to account for the accumulation of morethan 250 meters of shallow-water limestone, the top 123meters of which are peritidal. Limestone could have beencontinuously deposited under shallow-water conditions asthe system is basically self-regulating. Given reasonableconditions for the production of skeletons, the raw materialsfor most carbonate rocks, carbonate shelf margins canpotentially accrete vertically in pace with all but the mostrapid rises of sea level. This accretion rate cannot, ofcourse, exceed the subsidence rate or the shelf accretes tosea level and the carbonate factory is temporarily closed.

Subaerial exposure following deposition of fenestrallimestone (unit 2) marks the cessation of shallow-watersedimentation on the Blake Nose. Although this event is notyet well dated, on the basis of the general aspect of thefossils it is probably no older than Neocomian. Inasmuch aspelagic sediments were deposited immediately above theeroded limestone surface, extremely rapid subsidence orrelative sea-level rise during the Barremian must simplyhave submerged the Blake Nose below the very shallowdepths necessary for rapid carbonate production. This"drowning" was geologically rapid as no shallow-watercarbonate accumulated following exposure. Currents mayhave prevented deposition over the eroded surface untilBarremian pelagic sediments began to accumulate.

GEOCHEMISTRY

We analyzed only one interstitial water sample from thissite to determine pH, alkalinity, chlorinity, salinity, andmajor cations (Table 5). We did not collect samples forstudy of organic geochemistry because the sediment ismainly white limestone. No gas was detected in cores fromthis site.

PHYSICAL PROPERTIES

We drilled two holes at Site 392. Hole 392 wasterminated at 60 meters sub-bottom when we found thatthere was insufficient soft sediment cover to properly burythe bottom-hole assembly. Hole 392A was drilled to asub-bottom depth of 349 meters through 99 meters of softCretaceous calcareous ooze and 251 meters of dense, hardlimestone.

Sonic velocity, water content, porosity, and wet bulkdensity were determined for samples from Hole 392A; dataare compiled on Tables 6 and 7. Core recovery, however,was very poor (only 9%) and soft interbedded sedimentsmay have been washed away during drilling, hence thephysical properties data may not be representative of theentire sequence.

We recognized four lithologic units at this site andaverage values for the physical properties data for each unitare given in Table 8.

Sonic Velocity and Impedance

Sonic velocities were measured on 24 samples using theHamilton Frame velocimeter following the proceduredescribed by Boyce (1973). Accuracy of the technique is±2 per cent, and precision of the velocimeter was verifiedwith 10 repeated measurements of lucite and brassstandards. Velocities were measured parallel to bedding inthe upper four cores of calcareous and marly ooze. In thefew cases where orientation was preserved in the hardlimestones velocities were measured perpendicular tobedding (Cores 5 and 6, in part). Most of the limestone wasrecovered in chunks and pieces in which the originalorientation was totally lost. Thus, direction of velocitymeasurements below Core 8 is not known.

We determined impedance at points where both velocityand density data were available (12 data points). Densitywas determined by the "syringe" technique (Cores 1-4) andthe "chunk" technique described in Site 391 PhysicalProperties report. The average velocity and impedance foreach lithologic unit are given in Table 8.

We have insufficient data points to speculate on trendswithin the three limestone units (only a total of three datapoints for velocity in units 3 and 4). A very marked velocityand impedance "b reak" occurs between the softnannofossil ooze and clay of unit 1 (1.67 km/sec; 2.43gm/cm2 sec × 105) and dense limestones of unit 2 (5.85km/sec; 16.2 gm/cm2 sec × 105). This corresponds to aprominent reflector at 0.115 sec.

Velocity and impedance measurements on Cretaceouslimestones from lithologic units 2, 3, and 4 areexceptionally high (velocity ave. = 5.55 km/sec,

Sample

IAPSO STD SeawaterSurface Seawater

392A-3-4, 140450m

Sub-Bottom DepthTop (m)

82.2

TABLE 5Summary of Interstitial Water Data, Hole 392A

pH

7.878.417.58

Alkalinity(meg/kg)

2.362.412.61

Salinity(0/00)

35.236.336.3

Ca++

(m Moles/1)

10.5510.8810.71

++mg(m Moles/1)

53.9959.4152.19

Cl"(0/00)

19.3819.7719.90

349

SITE 392

TABLE 6Sonic Velocity Measurements, Hole 392A

Sample(Interval in cm)

1-2, 761-2, 1322-1,633-2, 1073-2, 1303-3, 253-3, 823-3, 1355-1, 1445-1,1445-2, 475-2, 476-1, 1296-1, 1298-1, 1409-1,54

10-2, 14111-1,5511-1,13116-1, 14417-1,5021-1, 11922-1, 10923-1, 75

Depth inHole (m)

52.7653.3266.6381.5781.8082.2582.8283.3599.4499.4499.9799.97

108.79108.79127.90136.54141.91146.05146.81184.94193.50232.19241.59250.75

Velocity(km/sec)

1.62 (in liner)1.65 (in liner)1.61 (in liner)1.70 (in liner)1.72 (in liner)1.70 (in liner)1.68 (in liner)1.69 (in liner)5.52a (out of liner)5.87 (out of liner)5.53a (out of liner)5.73 (out of liner)5.73a (out of liner)5.66 (out of liner6.38 (out of liner)5.70a (out of liner)6.1 l a (out of liner)5.52a (out of liner)5.98a (out of liner)6.21a(outof liner)6.07 (out of liner)5.97 (out of liner)5199 (out of liner)4.72 (out of liner)

Impedance(g/cm2 sec × 105)

2.56

1.673.25

2.25

15.13

17.1615.22

15.9716.5816.2716.0015.93

LithologicUnit

111111112222222222222334

Lithology

Foraminifer-nannofossil oozeForaminifer-nannofossil oozeMarly nannofossil oozeNannofossil oozeNannofossil oozeNannofossil oozeNannofossil oozeNannofossil oozeFenestral lime mudstoneFenestral lime mudstoneIntraclastic skeletal, lime packstoneIntraclastic skeletal, lime packstonePelletoidal lime grainstonePelletoidal lime grainstoneLimestoneLimestoneLime mudstonePelletoidal lime packstonePelletoidal lime packastoneLimestoneLime packstoneOolite-lime grainstoneOolite-lime grainstoneLimestone

Measurements perpendicular to bedding.

TABLE 7Water Content, Porosity, and Wet Bulk Density, Hole 392A

Sample Depth in Water Content Wet Bulk Density Porosity Lithologic(Interval in cm) Hole (m) (%) (g/cc) (%) Unit Lithology

1-2,2-1,3-2,3-3,4-1,5-2,6-1,7-1,8-1,9-1,

10-2,11-1,15-1,16-1,17-1,19-1,20-1,21-1,22-1,

78.562.5106.582.5119.5114.0129.0137.0137.054.026.0131.0134.0147.050.0132.0135.0118.0109.0

23-1, 106.0

52.7966.6381.5782.8389.70

100.64108.79118.37127.87136.54140.76146.81177.34184.97193.50213.32222.85232.18241.59251.06

24.027.523.819.328.7

0.61.71.20.71.01.41.16.61.00.60.70.70.81.11.7

1.581.041.911.341.342.702.642.672.692.672.662.672.432.672.682.682.692.682.662.65

38.028.545.425.938.5

1.74.53.12.32.83.82.9

16.12.61.51.92.02.12.94.6

11111222222222223334

Nannofossil oozeMarly nannofossil oozeMarly nannofossil oozeNannofossil oozeNannofossil oozeLimestonePelletoidal lime grainstoneLime packstoneLimestoneLime mudstoneLimestoneLimestoneLimestoneLimestoneLimestonePelletoidal lime grainstoneOolite-lime grainstoneOolite-lime grainstoneOolite-lime grainstoneLimestone

TABLE 8Average Sonic Velocity, Water Content, Wet Bulk Density, and Porosity, Site 392

LithologicUnit

1234

AverageVelocity(km/sec)

1.675.855.984.72

Range(km/sec)

1.61-1.725.52-6.385.97-5.99

4.72

No. ofMeasure-

ments

81321

AverageWater Content

(%)

23.51.50.91.7

Range(%)

19.3-28.70.6-1.70.7-1.1

1.7

No. ofMeasure-

ments

51131

Average WetBulk Density

(g/cc)

1.442.652.682.65

Range(g/cc)

1.04-1.912.43-2.702.66-2.69

2.65

No. ofMeasure-

ments

51131

AveragePorosity

(%)

35.33.92.34.6

Range(%)

25.9-45.41.5-16.12.0-2.9

4.6

No. ofMeasure-

ments

51131

350

SITE 392

impedance = 16.03 (g/cm2 × sec × 105) and are in generalagreement with velocities assumed from seismic profiles(5.0 km/sec).

Water Content, Porosity, and Wet Bulk Density

Procedures for determining water content, porosity andwet bulk density are discussed in the Site 391 report, thisvolume. Determinations were made on 20 samples fromHole 392A. Data are presented on Table 7 and averagevalues for each of the four lithologic units are given in Table8. As would be expected there is a marked break in all threeproperties between sediments of unit 1 (soft ooze) and thoseof the underlying limestone. The limestone is quite dense(2.43-2.68 g/cc) and generally has low porosities(0.6-1.1%), which no doubt are responsible for the highvelocities. Most original fenestral and shelter porosity hasbeen filled with two generations of cement.

GRAPE

Measurements of wet bulk density and porosity weretaken on samples of known dimensions with the GammaRay Attenuation Porosity Evaluator (GRAPE). Samplesfrom Hole 392A below Core 4 were lithified rocks andcould be removed from the liners allowing specialtwo-minute counts to be made on selected samples, therebydiminishing the variation encountered by continuous scan.GRAPE data were collected on 15 sections in Hole 392A.GRAPE data are graphically presented with the visual coredescriptions and core photographs at the end of this chapter.

BIOSTRATIGRAPHY

Site 392 is situated approximately 15 km south of Site390 on the Blake Nose. The objectives of Holes 392 and392A were to sample the reef-like limestones which nearlyreach surface here. We drilled to a total sub-bottom depth of349 meters and recovered 35 cores — two in Hole 392 and33 in Hole 392A. (We did not recover sediment in Cores 32and 33.) The water depth at Site 392 is 2601 meters, wellabove the CCD.

Well preserved foraminifers and nannofossils arecommon to abundant in the ooze above the hard limestonewhich allows detailed biostratigraphic determinations inHole 392A.

In Hole 392, the two cores taken near the surface are amixture of ooze, hard limestone, and manganese chips orpebbles. Quaternary, middle Eocene, and Upper Cretaceousnannofossils, and foraminifers are present. The limestonehere is probably capped by a veneer of Cretaceous, Eocene,and Quaternary sediment with manganese pebbles andreworked fossils.

The biostratigraphic succession in Cores 1-4 in Hole392A of four nannofossil zones and six foraminifer zonesresembles the succession in Hole 390, Cores 3 to 6 and390A, Core 14 (Figure 14). The zones comprise upperCampanian, middle-upper Albian, upper Aptian, andBarremian sediments. Differences are that at Site 392 lowerAptian (-Barremian) beds were not recovered and youngerAlbian strata are present.

The hard limestone in Cores 3 92A-5 through 31 yieldedonly a sparse foraminifer assemblage, mainly miliolids; nolarger foraminifers were found. The sediment is a very

Hole 390. 390A

200-

Figure 14. Chronostratigraphic correlation of Hole 392Ato Holes 390 and 390A,

shallow marine limestone of indeterminate age overlain byBarremian sediments. The Barremian deposits above areshallow-water limestone; the Aptian-Albian and upperCampanian ooze formed in a deeper, open marineenvironment.

Foraminifers

The two shallow cores taken from Hole 392 containQuaternary, middle Eocene, and Upper Cretaceousforaminifers. Well preserved upper Campanian toBarremian foraminifers are common to abundant in Cores392A-1 through 4 in nannofossil ooze and clay. Cores 5 to31, in hard limestone, have few foraminifers and none isage diagnostic. No sediment was recovered in Cores 32 and33.

The biostratigraphy of Lower Cretaceous foraminifers atSite 392 differs from that of Site 390 in the absence of the

351

SITE 392

• Frequent >50 specimensO Common, 10-49 specimensX Rare, 1-9 specimensC CavingsR Reworked

Sample(Interval in cm)

| |

U <

Planktonic Foraminifers

t |D. Sp

ti aj s; C

II I

ü θ O

•I s

•a ö o a

66.0-69.5

79.0-88.5

88.5-98.0

3.5

3.5

0.6

392A-2-1, 84-86392A-2-2. 146-148392A-2-3, 104-106392A-2 CC39 2A-3-1,46-48392A-3-3, 50-52*392A-3 CC392A-4-1, 110-112392A-4 CC

X OO O X

X

O X X X X O R X X O OO O O O X

O Xoo

R

• o• o x

o oo o0 X 0o

X O X

X X O O

* 392A-3-2, 121-123 cm belongs in the same zone.

Figure 15. Distribution and correlation of Lower Cretaceous foraminifers in Site 392.

lower Aptian G. blowi Zone, the possible presence of theupper Aptian S. cabri Zone, and the presence of the upperAlbian T. breggiensis Zone. The stratigraphic ranges of theLower Cretaceous foraminifers are shown on Figure 15 anddetails of the Lower Cretaceous foraminifer biostratigraphy(Sites 392 and 390) are given in Gradstein, this volume.

Upper Cretaceous

Sample 392A-1, CC: Globotruncana calcarata Zone,(UC11) upper Campanian

The core-catcher sample of Core 1 (50.5-53.2 m)contains Globotruncana calcarata, G. fornicata, G.linneiana group, G. marginata, G. aff. area, G.stuartiformis, G. ventricosa, G. aff. Gagnebini,Rugoglobigerina rugosa, and various hedbergellids andHeterohelicids. Benthic foraminifers are very sparse. Acomparable assemblage, also belonging in the upperCampanian G. calcarata Zone, occurs in Hole 390A, Core14-5.

Cretaceous

Samples 392A-2-1, 84-86 cm; 2-2, 146-148 cm; 2-3,104-106 cm; 2, CC: Ticinella breggiensis Zone (LCI7),upper Albian

Ticinella primula, T. breggiensis,* Hedbergellaamabilis,* H. planispira, H. aff. delrioensis, Gavelinellaintermedia group, Osangularia utaturensis, O. insigna,Pleurostomella obtusa, Valvulineria gracillima,Gyroidinoides primitiva, Epistomina spinulifera group, E.cretosa,* E. chapmani,* Reinholdella ultima,*Orthokarstenia shastaensis, * Dentaline debilis, * Lingulinaloryi,* Lingo gavelinella ciryi,* Dorothia gradata, D.oxycona.4

"Speciesmarked with an asterisk were not found in the Albian sedimentsof Site 390 (Ticinella primula Zone).

Sample 392A-3-1, 46-48 cm: Ticinella primula Zone(LCI5-16), middle Albian

Ticinella primula, Gavelinella intermedia group,Osangularia utaturensis, O. insigna, Epistominaspinulifera group, E. cretosa, E. chapmani, Reinholdellaultima, Orthokarstenia shastaensis, Lingogavelinella ciryi,Lamarckina lamplughi, Ceratolamarckina sp., Dorothiaoxycona, Gaudryina dividens group.

This assemblage differs from the immediately overlyingone (T. breggiensis Zone) in the absence of Ticinellabreggiensis, Hedbergella amabilis, and H. planispira andthe presence of Lamarckina lamplughi andCeratolamarckina sp. At Site 390 Hedbergella planispiraoccurs commonly in the T. primula Zone.

Sample 392A-3-3, 50-52 cm: Globigerinelloides algerianusZone (LC11), upper Aptian

Hedbergella trocoidea, Globigerinelloides algerianus,Conorotalites aptiensis, Lenticulina turgidula, L.vocontiana, Dorothia gradata, Gaudryina dividens group,Gavelinella intermedia group.

Sample 392A-3, CC: Schackoina cabri-Globigerinelloidesalgerianus Zone (LC10-11), upper Aptian

Same as in Sample 392A-3-3, 50-52 cm and alsoGlobigerinelloides aff. saundersi, G. ferreolensis, andLeupoldina pustulans which are restricted to this sample.

Sample 392A-4-1, 110-112 cm; 4, CC: Gavelinellabarremiana- Lenticulina (Marginulopsis) sigali assemblage(LC8, pp) Barremian

Conorotalites aptiensis, Gavelinella barremiana,Lenticulina ouachensis group, L. meridiana, L.(Marginulopsis) sigali, L. nodosa, Trocholina sp.

The exclusively benthic assemblage correlates to 390-6-1(slurry) and 390-6, CC where it is more diversified in

352

SITE 392

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Foraminiferal Stratigraphy

BenthosZone

group

G. barremiana- L. sigali

"2 .S

c c

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LC 17

LC 15-16LC 11

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Age

Late Albian

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Late Aptian

Figure 15. Continued.

species and includes "Globigerina" hoterivica (in 390-6,CC), Epistomina spp., Conorotalites intercedens (in 6,CC), andLenticulina crepidularis (in 6, CC).

Cores 392A-5-31: age indeterminateMiliolids are common in Cores 5 through 31 in addition

to a few simple arenaceous and/or calcareous benthicforaminifers of indeterminate age.

Nannoplankton

Manganiferous sediment and ooze containing upperQuaternary, middle Eocene, and Cretaceous sediment wasrecovered as drilling breccia in the two cores of Hole 392.Core 392-2 is questionably assigned to the combinedGephyrocapsa oceanicalEmiliania huxleyi zonal interval(NN 20/21), although drilling may have mixed the oozes.

In Hole 392A, the uppermost four cores contain upperCampanian and Albian-Barremian nannofossil oozes inwhich well preserved nannofossils are common toabundant. The nannofossil biostratigraphy of the Cretaceousooze of Hole 3 92A is comparable to Hole 3 90A in which anAlbian/upper Campanian hiatus is also present.

An abundant and well preserved flora of the Tetralithus(upper Campanian) trifidus Zone was recovered from Core392A-1. Core 392A-2 contains a flora of the early-middleAlbian Prediscosphaera cretacea Zone. Core 392A-3 isassigned to the upper Aptian-lower Albian Parhabdolithusangustus Zone. Core 392A-4 contains an assemblage ofwell preserved nannofossils of the BarremianMicrantholithus hoschulzi Zone. An increasing abundanceof nannoconids and pentaliths in Cores 3 92A-2 to 392-4may indicate a trend toward general shallowing inprogressively older sediments.

Depositional Environment

We recognize three different depositional environmentsat Site 392 on the basis of microfossil assemblages: (1)Barremian and/or pre-Barremian very shallow marine

conditions; (2) Barremian shallow-water conditions, and (3)a late Aptian to late Campanian deep marine realm (seeFigure 16).

The microfossil assemblage in the Barremian limestoneunit below Core 4 to the bottom of the hole consists ofnumerous miliolids and a few simple arenaceous orcalcareous foraminifers (all recrystallized tests). Such afauna may occur in very shallow water — possibly marginalmarine environments. Sedimentologic evidence discussedin the lithology section above, also suggests that theenvironment was one of very shallow water. No largerforaminifers (Orbitolina, Pseudocyclammina, Choffatella,or possibly Anchispirocyclina) were found. Fluctuatingsalinities, shallow water (? tidal flat), or high energyconditions may have been too extreme for them to havelived here.

The Barremian microfossil assemblage in Core 4 containsa great deal of skeletal debris from echinoids, mollusks, andalgae or sponges along with a low diversity benthicforaminifer assemblage (mainly lenticulinids and noepistominids). Nannoconids are especially common amongthe nannofossils. The environment was apparently shallowmarine, possibly 50 meters or less water depth.

Upper Aptian, middle-upper Albian, and upperCampanian sediments are clayey nannofossil oozes whoseforaminifer content indicates that the water was muchdeeper when they were deposited. The highplankton/benthos ratio with a negligible number of benthicforaminifers (especially in the upper Campanian sediments)indicates an open marine environment in at least 500 metersof water.

SEDIMENT ACCUMULATION RATES

Sediment accumulation rates in Hole 392 can becalculated only for the Barremian to Albian intervalbetween Cores 4 to 2. The absence of biostratigraphiccontrol in the almost 250 meters of Barremian or older

353

SITE 392

Microfossilassemblage

69.5

82.5

99.7-

200-

Nannofossil-foraminiferooze; almost no benthos

as above withmore benthos

Low diversity forambenthos assemblageskeletal debris ofmacrofossils

Miliolid-, andsimple arenaceousand/or calcareousforaminifers

Figure 16. Stratigraphy and depositional environments, Hole 392A.

354

SITE 392

limestone in Cores 5 to 31 precludes calculations. Thethickness of the upper Campanian beds is unknown.

If we assume that half of the Barremian, all of the Aptian,all of the lower-middle Albian, and half of the upper Albianoccur in or between Cores 392A-4 through 3 92A-2 and thatthe Albian-late Campanian hiatus is halfway between Cores2 and 1, late Barremian to late Albian sedimentationaveraged 0.2 cm/1000 yr. This is the same rate as in Site390 (Figure 17).

As Sites 390 and 392 are close together, the similarity inthe mid-Cretaceous water depths (Figure 24 in the Site 390chapter and Figure 16, this chapter) is reasonable andsubsidence rates are about the same at the two sites.

CORRELATION OF DRILLING RESULTSWITH SEISMIC REFLECTION PROFILE

As Glomar Challenger approached Site 392, an airgunseismic profile was run on a course of 300° (Figure 18)following the line made in the original survey of Site 389.The profile shows the distinct seismic character of the roughhyperbolic reflector which is opaque to acoustic

transmission and is interpreted to be a reef-bank or rimcomplex. Just west of the 3 km-wide reef-complex,sedimentary reflectors as deep as 4.5 sec appear abruptlyfrom within the apparently more massive structure. Thesesedimentary layers can be traced to Site 390 to allowcorrelation between the two Blake Nose sites.

Two reflectors were penetrated by Hole 392A: one at0.07 sec and one at 0.115 sec sub-bottom. The opaque zoneoriginally thought to be reef-complex limestone is belowthis. The 0.07-sec reflector is correlated with theunconformable interface between the Campaniannannofossil ooze and the firm Aptian-Albian sticky clay andooze. This correlation gives a reasonable calculated velocityof 1.57 km/sec for these near-surface Campanian andyounger oozes.

The next deeper reflector above the opaque zone at 0.115sec sub-bottom is correlated with the rubble-zone contact ofthe hard limestones just below the Barremian nannofossilooze. This correlation gives a calculated velocity of 1.78km/sec for the Aptian-Albian to Barremian ooze unitoverlying the limestone.

CRETACEOUS TERTIARY QUAT.-

Early Late Early Late

Ber. Val. Haut. Barr. Apt. Alb. Cen. Tur. Con. Sant. Camp. Paleo.E I L

EoceneE I M I L

OligoceneE I L

MioceneE | M | L

120 115 108 100 92 86 81 76 70 65 60m.y.

53.5 49 43 37.5 22.5 5 1.8

10

50

100

150

\

\

N H

HFNl—I

\ _

1 -

V777\ Y777X rπ P77I

-

Figure 17. Rate of sediment accumulation, Site 392.

355

SITE 392

100

200-

300-

J l h .

?

L_r.

i_

VEL.

11.!

1.

57

78

\

Figure 18. Correlation of lithology with seismic reflection profile, Site 392. Velocitiesare calculated on basis of correlation of reflectors with drilled boundaries.

No other deeper reflectors were observed on the Site 392Challenger profile. On the basis of an assumed 5.0 km/secvelocity for the hard limestone we infer that Hole 392A onlypenetrated to about the equivalent of 0.215 sec sub-bottom.

SUMMARY AND CONCLUSIONS

Our return to the Blake Nose gave us an opportunity tocollect more definitive evidence on the history ofCretaceous reef-bank rim-complex. The evidence from theholes drilled at Site 390 allowed us to develop a reasonablemodel of reef-complex development, but it is not exclusiveand relies entirely on seismic extrapolation from Site 390 tothe inferred reef complex some 25 km away. Also, in thatmodel several seismically identified layers of possibleCenomanian to Santonian(?) age, thought to be present onthe Blake Nose, could not be correlated definitively becauseof the Campanian/Albian hiatus at Site 390.

We planned to sample some of theseCenomanian-Santonian beds at Site 392 — if they indeedreached that site — to penetrate the reef complex to severalhundred meters and to study the carbonate microfaciespresent.

Drilling at Site 392 recovered a section of ooze overlyinghard recrystallized limestone of near-reef or at leastnear-shore peri-reefal facies (Figure 19). No Santonian toCenomanian sediments were found. The hiatus in theCretaceous oozes is from Campanian to Aptian and the oozeoverlying the hard limestone is of Barremian age, both as atSite 390.

Drilling at Site 392 penetrated 260 meters of hardlimestone, the upper 10-15 cm of which has been

brecciated, weathered, and cemented by iron oxides. Theupper zone also contains small concretionary, pisolites oflimonite. Discovery of coccoliths incorporated in thesepisolites indicates that they formed in an open marineenvironment.

The limestone itself comprises three lithologic types, allof which were deposited in shallow-water. The top 113meters was deposited in a tidal flat environment, possiblybehind an island barrier which provided a wave-protectedlagoon. All the limestone has been recrystallized and someof the secondary features are diagnostic of alteration abovethe water table. The lower part of the section is cavernouswhich also suggests solution by meteoric waters.

The simplest model for the deposition of the limestonesequence is a single cycle starting with a shelf or bank,gradual shoaling to tidal flats, and final exposure tosubaerial weathering. Several features associated with thesolution and recementation of certain beds, however,suggest that this simple model may have been complicatedby more than one emergence above sea level andconsequent subaerial diagenesis. In view of the worldwidefluctuations of Cretaceous sea level, several emergencesvery likely took place.

Cretaceous Reef Building on the Blake Nose

The results of drilling at Hole 3 92A and the correlation ofseismic profiles gives a final interpreted cross-sectionof the Blake Nose (Figure 20). Note that we infer thatSantonian-Cenomanian sedimentary layers probablyunderlie the northwest portion of the Blake Nose, and that

356

SITE 392

Core No.

Hole Hole392 392A

Lithology Age

BIOSTRATIGRAPHIC ZONES

Foraminifer Nannoplankton Radiolarian

Velocity(km/sec)

Drilling rate(m/hr)

-I 1—I—I 1—1~

10 20 30 40 90 140

100

3 0 0 -

I

SA

JL •x

18A

19A

20A

22A

24A

'δ' I

'§' ' t9'

CAMPANIAN

Nannofossil ooze G. calcarata T. trifidus

Nannofossil oozeand clay

ALBIAN

U. APTIAN

BARREMIAN

T. berggensisT. primula

G. algerianusLsigali

P. angustus

M. hoschulzi

Fenestrallimestone

NEOC. (?)and/orOLDER

Oolite

Microcrystalline skeletallimestone

(cavernous zone)

1.55*

I(1.67)

1.78*(1.67)

(5.85)

(5.98)

(4.72)

"Calculated value

Figure 19. Graphic hole summary, Site 392.

5.0

Figure 20. Interpreted geologic cross-section of the Blake Nose on basis of Sites 390 and 392 drilling.

357

SITE 392

the same Campanian/Albian hiatus of Site 390 is alsopresent at Site 392.

Drilling at Site 392 did give definitive data on thetermination of the reef bank-rim complex buildup. Theupper contact of the tidal-flat fenestral limestone is anerosion surface directly overlain by deeper marineBarremian sediments. In fact, the overlying Barremian,Aptian-Albian, and Campanian sediments all record anincreasingly pelagic and deep-water environment. Clearlyshallow-water bank-margin carbonate deposition on theBlake Nose did not continue through Barremian time.

This termination shallow-water carbonate accumulationmight explain the difference in present depth between thereef-bank complex on the Blake Nose, at about 2650meters, and the margin bank complex on the lip of the BlakeEscarpment from just south of the Nose to the area of GreatAbaco Canyon, at about 1500 meters. If these reefcomplexes were of the same age, the Blake Nose blockwould have had to have faulted downward relative to therest of the Blake Plateau (Ewing et al., 1966). Thetermination of reef-bank rim complex buildup on the BlakeNose by Barremian time contrasts with the possibleCenomanian-Campanian age for the 1500 meter rimcomplex along the rest of Blake Escarpment (Sheridan etal., 1971). Dredging just below this 1500-meter liprecovered Upper Cretaceous ostracode-rich miliolidlimestone, probably a lagoonal facies of the rim complex,and Albian miliolid limestone at 2300 to 2400 meters(Heezen and Sheridan, 1966). From this we infer that theshallow-water platform complex persisted until Campanian(?) time along the escarpment but had ceased to form on theBlake Nose by the end of Neocomian or at Barremian time.This interpretation does not require faulting or any otherstructural adjustment to lower the Blake Nose relative to theBlake Plateau.

REFERENCESBartenstein, H. Bettenstaedt, F. and Bolli, M. H., 1957. Die

Foraminifern der Unterkreide von Trinidad, B.W.I, teil I:Eclog. Geol. Helv., 50, (1), pp. 5-65.

Bolli, H. M., 1966. Zonation of Cretaceous to Pliocene MarineSediments Based on Planktonic Foraminifera: Bol. Inform.Assoc, Venezuelana Geol. Miner. Petrol., v. 9, no. 1, p.3-32.

Boyce, R.E., 1973. Physical properties -methods. In Edgar, N.T.,Saunders, J.B., et al., Initial Reports of the Deep Sea DrillingProject, Volume 15: Washington (U.S. Government PrintingOffice), p. 1115-1124.

Enos, Paul, 1974. Reefs, platforms, and basins of the MiddleCretaceous of northeast Mexico, Am. Assoc. Petrol. Geolog.Bull., v. 58, p. 800-809.

Ewing, J. I., Ewing, M. and Ley den, R., 1966. Seismic ProfilerSurvey of the Blake Plateau: Amer. Assoc. Petrol. Geol. Bull.,v. 50, p. 1948-1971.

Heezen, B. C. and Sheridan, R. E., 1966. Lower CretaceousRocks (Neocomian-Albian) Dredged from Blake Escarpment:Science, v. 154, pp. 1644-1647.

Lancelot, Y., Hathaway, J.C., and Hollister, C D . , 1972.Lithology of sediments form the Western North Atlantic, LegXI. In Hollister, D.C., Ewing, J.I., et al., Initial Reports of theDeep Sea Drilling Project, Volume 11: Washington (U.S.Government Printing Office), p. 901-950.

Meyerhoff, A.A. and Hatten, C.W., 1974. Bahamas salient ofNorth America. In Geology of Continental Margins, Burk,C.A. and Drake, C.L., (Eds.), New York, (Springer Verlag),p. 429-446.

Schlee, J., Behrendt, J.C., Grow, J.A., Robb, J.M., Mattick,R.E., Taylor, P.T., and Lawson, B.J., 1976. Regionalframework off northeastern United States, Am. Assoc. Petrol.Geol. Bull., v. 60, p. 926-951.

Sheridan, R. E., Berman, R. M., and Corman, D. B., 1971.Faulted Limestone Block Dredged from Blake Escarpment:Geol. Soc. Amer. Bull., v. 82, p. 199-206.

Sigal, J., 1966. Contribution a une Monographic der Rosalines I leGenre Ticinella reichel, souche des Rotalipores: Eclog. Geol.Helv., v. 59, no. 1, p. 185-218.

Simon, W. and Bartenstein, H. et al., 1962. Leitfossilien derMikropalaontologie Gebr. Borntraeger, Berlin,

van Hinte, J. E., 1972. The Cretaceous Time Scale and PlanktonicForaminiferal Zones: Proc. Kon. Nederl. Akad. Wetensch.,ser. B, v. 75, no. 1, p. 1-8.

358

SITE 392

Hole 392 Core 1 Cored Interval: 47.5-57.0 m

I I FOSSIL I I I E J ~ δ lo ^ ^ CHARACTER

g |gg|g

?£ § £ S £ y LITH0L0GY It^lS^ LITHOLOGIC DESCRIPTION

ë M § I g g 5 SS^U^ëM o <C •< ^ uj h- D:M I—ica:1— U _ Z Q : toooQQ n/)

_2 - MANGANESE NODULES AND LIMESTONE FRAGMENTS

^ Total recovery consists of fragmented piecesg I of rock of several different lithologies•c *-» 0.5— including:g § - VOID§ £ 1 1) MANGANESE NODULES, dull black with rough" ^ 3 ~ surface and indistinct laminations, to 5 cm£, w ' ° 1 ^-^ diameter. Nodules are from present sediment

- ^ °° surface as evidenced by encrusted living~ <S)/nx(HSp) v ^^ anemone.

" - 2) LIMESTONE, white (10YR 8/2), soft, muddyor silty with planktonic forams which havebeen partially Mn coated.3) LIMESTONE, angular, hard, with partiallycemented lithoclastic texture, clear to milky-spar cement, high porosity in form of shelterpores.4) LIMESTONE, pale yellow (TOY 7/3), spongywith irregular shelter pores.5) Lustrous to coarsely crystalline CARBONATECRUSTS with pisolites and belemnites.6) Dense INTRACLASTIC LIMESTONE , ery palebrown (10YR 8/3) with rounded to angularmicrite clasts.7) Porous INTRACLASTIC LIMESTONE, withshelter pores.

Hole 392 Core 2 Cored Interval: 57.0-60.0 m

"~ FOSSIL I I F ~ T ~ 3 I

i== o Σ O h £ LITHOLOGY ë t ~ i o ^ LITHOLOGIC DESCRIPTION

•-1 o = c < c 1 ^ ^ LUI--CI:I-I i—i=ti— ü _ z α : I Λ W D Q —ICΛ

I LIMESTONE

o ° JYI o

: /^BIRDSEYE" LIMESTONE, pale yellow (5Y 8/3)° | /with distinctive "birdseye" porosity. Lime

° 5~

o DRILLING / mudstone and packstone laminae. Matrix is

A_ç j - BRECCIA0 ; ^ / carbonate mud, skeletal fragments and- oAND / grapestone. Skeletal fragments are molds(?)

1.0— SLURRY » ^ / of pelecypods, gastropods(?), ostracodes(?)- o o x 2 / replaced by clear spar. Clear blocky sparI ° / f i l l s "birdseye" pores.

_ 2 o o / /^BIRDSEYE" LIMESTONE (mixed pieces of twpSZ - Iff types).

c o ^ 1 ° × I // 1) LIME PACKSTONE AND GRAINSTONE of p e l l e t o i d sg ^ g ~ o x °°__/ yy and grapestone aggregates. "Birdseyes" are£ ^. o o - ' i-,' Tr)1— ×* // predominantly shelter pores-vertical pores^ CM ^ - ^ r | i A Cl p) ^ >~ // formed in cohesive muddy layers by gas escape~ 5 i A G A r ~ DELING )T " 7 or mud crackling.

A-fa A-G - I oBRECCIA,? X / 2) LIME "MUDSTONE" AND WACKESTONE, w i t h mud- i , | , i \ invR \IÙ. c'raPes (a^9ae formed "birdseye" structure?),I » I ' \ ' " ^ / ^ ^ °/* large grapestones in mud (145-148 cm), coarse~ ' ' il 1 *~s-J \\yiK if6 c lea r spar f i l l s pores ; po ros i t y now near 0%.

CC I

360

SITE 392

1

r—

-

-

-

-

-

-

-

—

-

DENSITY (gm/cc)SONIC VELOCITY (km/sec)

2 31 ' 1

4

1

m0 -

1 -

2 -

3 -

4 -

•7

6 -

7 -

8 -

9 -

Site 392SECTION

cmr-o

- 2 5

- 5 0

- 7 5

-100

•125

-150> gravimetric wet-bulk density © undifferentiated sonic velocity

- ^ parallel sonic velocity -—continuous GRAPE-f- F>erpendicular sonic velocity

\

2-2

361

SITE 392

Hole 392A Core 1 Cored Interval: 50.5-60.0 m

FOSSILCHARACTER

LITHOLOGY LITHOLOGIC DESCRIPTION

VOID

0.5-

1.0-

ooo

- 2

— *

A-GA-G

CC

NANNOFOSSIL AND FQRAM OOZE

CALCAREOUS OOZE, pale yellow (5Y 7/3), firm,structureless, planktonic foraminifer are commonprobably some clay (gray smears). Clear areasof ±20ytn may be gas bubbles.

NANNOFOSSIL OOZE, pinkish white (5YR 8/2)soft, structureless.

FORAMINIFER-NANNOFOSSIL OOZE, very pale brown(10YR 7/3), firm, structureless. Contains

terrigenous material.

NANNOFOSSIL OOZE, pinkish white (5YR 8/2)_soft, structureless.

FORAM-NANNOFOSSIL OOZE, very pale brown (10YR8/4, 8/3), firm, indistinct layering of colorand coarse laminae containing more forams.

Carbonaceous mud blebs.

Smear Slides

QuartzFeldsparMicaHeavy Mins.Clay Mins.Vole. GlassPyriteZeolitesForaminifersNannofossilsCarb. RhombsCarb. Unsp.Other Calc. FrgsSpg. Spies.

Carbon-Carbonate

2-20

CaC03 87.0Org. C 0.0Total C 10.6

CaCO, (Bomb) at

1-97

R

TTAT(?)

RA

C

{%)2-95

91.00.0

10.9

1-95 =

1-105

R

RRC

TTCATCRT

Grain

SandS i l tClay

91%; at

1-138

R

RRC

TRCARC

Size (

1-110

2-30

TTR

C

RT

2-111

T

T

C

R(B+P) CA

C

;*)1-81

23067

= 93%

A

R

2-42

33265

362

SITE 392


2 3

Site 392A

SECTION4 cm

m0 -

1 -

2 -

3 -

4 -

5 -

6 -

7 -

8 -

9 -

- 2 5

- 5 0

- 7 5

-

.:

- 1 0 0

- 1 2 5

- 1 5 0

0 gravimetric wet-bulk density © undifferentiated sonic velocity- ^ parallel sonic velocity -^—continuous GRAPE4f perpendicular sonic velocity

1-1 1-2

363

SITE 392

Hole 392A Core 2 Cored Interval : 66.0-69.5 ir

i£DRILLING_^SLURRY ~

LITHOLOGIC DESCRIPTION

1OYR 4/1- 5Y 6/1

10YR 4/1to5G 4/1

t 5Y 6/15G 4/1&5Y 6/1&10YR 4/15Y 7/2&5Y 6/3

MARLY NANNOFOSSIL OOZE

MARLY NANNOFOSSIL OOZE, dark gray (10YR 4/1),dark greenish gray (10YR 4/1), mixture oflight gray (5Y 7/2) and pale olive (5Y 6/3),(probably mixed by drilling), soft, plastic,structureless. CALCAREOUS SILTY CLAY at 110 cm,Sect. 1.

Smear Slides1-85 1-110 1-128 2-119

Quartz C CFeldspar RMica R CHeavy Mins. R RClay Mins. A AOpaque Mins. RVole. Glass TFe-oxidesPyrite R TZeolites TForaminifers R TNannofossils A CCarb. Unsp. C RCarb. RhombsOrg. Matter R

Carbon-Carbonate (%)

1-55 3-53

CaC03

Org. CTotal C

45.0 42.00.6 0.15.9 5.1

Grain Size

SandSiltClay

1-64 3-60

2 129 2769 72

(Bomb)

1-71 2-115

45 38

364

SITE 392

1

I

-

>

-

-

-

-

-

-

-

—


2 3

I ' I

Θ

>

4

1

m0 -

1 -

» -

3 -

4 -

5 -

fi —

7 -

8-^

9 -

SECTIONSite 392A

h '

- 2 5

- 5 0~ù

- 7 5

-100

-125

i 'I

^150

t> gravimetric wet-bulk density © undifferentiated sonic velocity 2-1- ^ parallel sonic velocity -^—continuous GRAPE4- perpendicular sonic velocity

365

SITE 392

Hole 392A Core 3 Cored Interval : 79.0-88.5 m


MARLY NANNOFOSSIL OOZE, NANNOFOSSIL OOZE, ANDLIMESTONE FRAGMENTS

MARLY NANNOFOSSIL OOZE, dark gray (10YR 4/1),mottled./S~ëct. 2, 55-65 cm- Two limestone fragments

5Y 6/3 /are (1) FORAMINIFER LIME MUDSTONE, medium light10YR 4/1/ gray (N6) with lime packstone matrix and fine5Y 6/3 / laminae (mm) of pyritic packstone, possible

burrows.(2) FORAMINIFER LIME WACKESTONE, pale yellow(5Y 8/3), streaked with yellow (5Y 7/6), hard,dense, microvuggy (<1% porosity), some Mn stainin pores.N6

5Y 8/3

- 10YR 7/4

5YR 6/6

I0YR 8/210YR 7/4

NANNOFOSSIL OOZE, very pale brown (1OYR 8/3)with layering (±cm) of pale brown and yellow(10YR 8/6), and reddish yellow (5YR 6/6).

Smear Slides

QuartzFeldsparMicaHeavy Mins.Clay Mins.Fe-oxidesOpaque Mins.PyriteZeolitesForaminifersNannofossilsCarb. Unsp.Carb. Rhombs

2-85 2-135 3-21 3-136 3-142

Clast of white nannofossil ooze.

Carbon-Carbonate {%) Grain Size (%)1-26 1-47 2-87 1-75 2-108 3-84

CaC03 44.0 65.0 80.0 Sand 1Org. C 1.0 0.0 0.0 S i l t 26Tota l C 6.3 7.8 9.6 Clay 74

3 238 3359 65

CaCO, (Bomb) at 2-135 - 71%; at 3-11 = 70%.

366

SITE 392

1f

-

-

ö

Θ

Θ

> Θ

Θ

-

-

—

—


2 3

1

>

141

m0 -

1 i i

I

2 -

-

Qo

4 -

-

5 -

6 -

8 -

9 -

Site 392A

SECTION

h-25

•50

- 7 5

-100

-125

-150

> gravimetric wet-bulk density O undifferentiated sonic velocity- ^ parallel sonic velocity •«--»continuous GRAPE-f perpendicular sonic velocity

1 .

367

SITE 392


FOSSILCHARACTER

LITHOLOGY3=Q_


0.5 —VOID

C-G

C-M

1.0-

C-G

lOYR 8/3lOYR 6/6.lOYR 8/3:iOYR 6/45YR 7/4lOYR 8/3

CC

NANNOFOSSIL OOZE AND LIMESTONE

NANNOFOSSIL OOZE, very pale brown (lOYR 8/3)to brownish yellow (lOYR 6/6), f i rm, disturbedby dri11 ing, with:

LIME MUDSTOME (120-122 cm), brown (lOYR 5/3),containing planktonic forms.

AMMONITE LIME PACKSTONE (130-150 cm), l ightyellowish brown (lOYR 7/4) to pink, moderatelyhard and fragmented. Ammonites present(individuals are larger than diameter ofrocks), shell walls recrystallized to clearspar. Geopetal f i l l in one. Some porosityin shell walls, slight pyrite staining,planktonic foraminifers are common, shell frag-ments are present, one coral or coralline algaefound.OOLITIC LIME BRECCIA (core-catcher sample),angular limestone clasts with laminated, denseFe-rich rims. Clasts are stained red (5YR 5/8)and contain dark brown el l ipsoidal, concenticpisolites with large (to 75% diameter) irregularrusty nuclei i . Clasts contain numerous corals.Matrix is gray, dense, crystalling with numerouspisolites and some shell fragments.

Carbon-Carbonate (%)1-117

CaC03Org. CTotal C

54.00.06.5

368

SITE 392


Site 392A

SECTION4 cm1 1-0

H-25

- 5 0

- 7 5

- 1 0 0

- 1 2 5

—150

t> gravimetric wet-bulk density- ^ parallel sonic velocity-{- perpendicular sonic velocity

© undifferentiated sonic velocity-«— continuous GRAPE

369

SITE 392


FOSSILCHARACTER


0.5-

1.0-

VOID

VOID ><

LIMESTONE

PISOLITIC LIME BRECCIA, reddish stain, angularclasts, coral-rich, laminated Fe-rich crustforms surface across solution etched surface.

FENESTRAL LIME MUDSTONE AND PACKSTONE, (10YR7/4), muddy and grainy lenses and irregularlyalternating layers, shells of very thin walledpelecypods and gastropods.

INTRACLASTIC-SKELETAL FRAGMENT LIME PACKSTONE,pale yellow (5Y 7/4), fine-scale fenestral andshelter porosity filled with sparry calcite;pelecypods and some gastropods (one is geopetal).Clasts are grainstone, some with dense outer

LIMESTONE, more crystalline than above, smallangular flakes, vertical tube-gas escapestructure. Fracture and/or tube porositycommon (85-114 cm). Fenestral porosity abundant114-137 cm, spar-filled 114-121 cm.

SKEL-FRAGMENT LIME WACKESTONE, pinkishwhite (5YR 8/2), dense, skeleton molds aregastropods, some pelecypods, microcrystallinematrix.

Carbon-Carbonate

CaC03Org. CTotal C

7-72

87.00.110.5

Hole

TIME

-ROC

KUN

IT(Indeterminate)

(

i 392A

ZONE

^arbon-C

Core 6

FOSSILCHARACTER

FORA

MS

R

arbc

NANN

OS

mat

RADS

3 {%

1-82


SECTION

0

1

)

METE

RS1

1

0.5-

1.0—

-

Cored Interval:

LITHOLOGY

VOID

^• • '

SEDI

MENT

ARY

STRU

CTUR

ES

-\rPl~vA

DRIL

LING

DIST

URBA

NCE

_

107.5-117.0 m

LITH

OLOG

YSA

MPLE

- e


LIMESTONE

f~ SKEL-FRAGMENT LIME WACKESTONE, pinkish white/ (5Y 8/2), moldic porosity, spar-filled are

AM Q/9 gastropods abundant. (Lithology same as at

—r» o/i bottom of Core 5).

SKEL-FRAGMENT PELLETOIDAL L. GRAINSTONE,pinkish white (5Y 8/1). Lower boundary is

-* sharp erosional contact.

\ LIME MUDSTONE TO SKELETAL WACKESTONE,\ extensively cracked and broken to give intra-\ clastic breccia appearance. These probably\ from mud cracks, gas escape,and desication\ crumbling. Extensive fenestral porosity filled\ by clear spar; two cement generations.

Abundant small mud clasts or grapestone, andgas escape structure at 125 cm.

370

SITE 392


Site 392A

SECTION4 cm

1 ro

mO-i

5.53 5.86

5.53 5.732 -

3 -

1

r~—

-

-

-


2

1

>

3

1

4

1

m0 -

1 -

5.66 5.73

p _

3 -

- 2 5

- 7 5

•100

M 2 5

\> gravimetric wet-bulk density- ^ parallel sonic velocity-\- perpendicular sonic velocity

O undifferentiated sonic velocity-•^--continuous GRAPE

*

>

i

371

SITE 392


π i F°SSIL i i i I J d§ w CHARACTER § a ||g|§SI i s o S E LITH0L0GY i t ? l § ^ LITH0L0GIC DESCRIPTION5 α: •ZL Q ^ 5^ Q o: I-H oo i— SLXI O •=C <C ° ° •2" Ljµαi w<•~ u - 7 z . c c I Λ I Λ D D —ico

_ 5 - LIMESTONE

£> Entire recovery consisted of four pieces of1 _ LIME PACKSTONE, pink (5YR 8/3) with th in

'H 0.5— ygjQ muddy interbeds. Grains are m i l i o l i d s , i n t r a -5 1 c lasts , mollusk fragments, pel leto ids.% •l• - Extensive i n t e r p a r t i c l e or shelter porosity1- «_2 oo (now s p a r - f i l l e d ) with f l a t i n t r a c l a s t s ,^ü- ' * ü _ 2o burrows(?) (tubes 1 mm diam., ver t ica l and

- >- horizontal, single tubes or strings),R ~* ~ - j f ^ H ^ ^ X f ^ ^ F ~ 7 ^ desiccation crumbling, and gas escape tubes.


o CHARACTER §^CDSS

S i o s! o h E LITHOLOGY I t S I S j LITHOLOGIC DESCRIPTIONS- r v l C • 2 - 0 0 ! ^ UJ i-H D —IH X Q .^ cc ^ Q H ^ Q Q: -H CΛ •Σ.Zl O <C <c <" – UJ t—cü • I-HCI;>~ u _ ^ o i IΛMQD —loo

_2 I LIMESTONE

-2 ~ Six, small, white (5Y 8/2) limestone piecesJ - comprising four l i t h o l o g i e s :| °

5~ VOID

OJ j 1) PELLETOIDAL LIME GRAINSTONE, spar-filled

.cu - gastropod molds are common.

~, 1.0- 2) PELLETOIDAL LIME GRAINSTONE, with inter-

_ clasts and filled interparticle and shelter

R — — - ^ ^ ^ ‰ ^ ^ a' 0 Z^ ~ e cv o/o' ' ' ' ' ' ' w g " • ^ J T ö / 3) SKELETAL-INTRACLASTIC LIME WACKESTONE,

fenestral and moldic porosi ty, two generationsof cement.4) PELLETOIDAL-INTRACLASTIC LIME GRAINSTONE,fenestrae and molds are spa r - f i l l ed .Carbon-Carbonate {%)

1-136CaC03 100.0Org. C 0.0Total C 12.0

372

SITE 392

1

r~

—

—

-

-

-


2 3

1 ' I

>

4

1

m0 -

1 -

-

2 -

SECTIC

cm

r-o

1

I

—

-

-

-


2 3

1 ' 1

>6.37

Θ

4

1

m0 -

-

2 -

3 -

- 2 5

- 5 0

- 7 5

- 1 0 0

- 1 2 5

t> gravimetric wet-bulk density- ^ parallel sonic velocity-f> perpendicular sonic velocity

Φ undifferentiated sonic velocity

-—continuous GRAPE

373

SITE 392


FOSSILCHARACTER


t10YR 8/3

0.5-

1.0-

"V

β

Carbon-Carbonate

1-44

CaC03 96.0

Org. C 0.1Total C 11.6

LIMESTONE

LIME MUDSTONE, very pale brown (10YR 8/3)with intraclasts formed in site by disruption(desiccation?) of stiff mud layers. Vuggyand some moldic porosity partially filled bytwo generations of calcite. There are twosmall pieces of PELLETOIDAL INTRACLASTICLIME PACKSTONE with pelecypods at top.PACKSTONE with miliolids, pellets and smallintraclasts. Bottom contact is sharp. Thinwhite oxidized(?) zone overlies LIME MUDSTONEwith burrows concentrated at top.»>

SKELETAL INTRACLASTIC LIME PACKSTONE, withgastropod molds and few pelecypods andmiliolids. Vertical crack at 120 cm (gasescape?).

LIME MUDSTONE at 133-141 cm.

Irregular erosional surface at 141 cm.Truncated grains indicate lithificationpriorto erosion.


FOSSILCHARACTER


0.5-

1.0-

VOID

Vs!

-e

10YR 8/310YR 8/2

10YR 7/3


2-50

CaC03 100.0Org. C 0.1Total C 12.0

LIMESTONE

LIME WACKESTONE, (five small pieces - Sect. 1)very pale brown (10YR 8/3), with pelletoids,gastropods and intraclasts. Vertical andwavy series of spar-filled blebs are probablybeneath muddy layers.

Intercalated SKELETAL WACKSTONE and INTRA-CLASTIC and/or SKELETAL PACKSTONE. Laminaeare indistinct, irregular and with varyingthickness and lenticularity.

Extensive spar-filled porosity originatedas open burrows, mud cracks, gas escapetunnels, shelter pores which were enlargedto vugs in some cases probably by samesolution process which formed molds.

14-35 cm - Fine laminae of muddy and grainypackstone or grainstone with forams andpeletoids. Fenestral porosity, common.

46-150 cm - Grainy intervals (Packstone andgrainstone > wackestone) with miliolidsabundant in grainy layers. Distinctive greenalgae(?) common in this interval.

Thin white coatings on pelletoids and/orskeletal grains occur intermittantly betweenv60-150 cm.

374

SITE 392

1

r~

—

—

-


2 3

1 ' 1

>

41 1

m0 -

5.70

1 -

2

3 -

Site 392A

SECTIONcm

1

r~

—

-

-

-


2 3

I ' I

>

6.11

4

I

m0 -

1 -

2 -

4 -

Ml

- 2 5

- 5 0

- 7 5

- 1 0 0

- 1 2 5

— 150

5 1

H

r 1

i

r 1

t> gravimetric wet-bulk density © undifferentiated sonic velocity- ^ parallel sonic velocity -—continuous GRAPE-J- perpendicular sonic velocity

10-1 10-2

375

SITE 392


FOSSILCHARACTER


VOID

0.5 —

— e

120 cm - Polygonal pattern on horizontalsurface.137-150 cm - Muddy packstone. Network ofthin spar-filled cracks.


CaC03Org. CTotal C

1-10695.00.011.5

LIMESTONE

PELLETOIDAL-INTRACLASTIC LIME PACKSTONE, white(5Y 8/2), abundant fragments of pelecypods,miliolids, gastropods (all small and thin-walled) and with inter!ayers of SKELETALPELLETOIDAL LIME WACKESTONE and GRAINSTONE.Spar-filled fenestrae and vertical tubes

5Y 8/2 common. Abundance of these irregular poretubes gives entire rock a brecciatedgenerations throughout: (1) uniform druseencrusting walls, and (2) coarse blocky spargenerally filling pores.

71-83 cm - Muddy interval (packstone withindistinct pelletoids) and possible burrows.87-92 cm - Intraclastic grainstone layers;clast imbrication.103 cm - Grainstone layer. Geopetal in filledshelter pore.111-115 cm - Same texture as above, but re-crystallized, denser appearance.


TIME

-ROC

KUN

IT(Indeterminate)

ZONE

FOSSILCHARACTER

FORA

MS

NANN

OS

RADS SECTION

CC

METE

RS

-

LITHOLOGY

tfjflf> <?iA &mJ}>

SEDI

MENT

ARY

STRU

CTUR

ES

yQ

DRIL

LING

DIST

URBA

NCE

1

X X

LITH

OLOG

YSA

MPLE LITHOLOGIC DESCRIPTION

LIMESTONE

Pebbles of SKELETAL-INTRACLASTIC LIME PACKSTONE,extensive fenestral porosity, incompletelyfilled by second generation cement. Remnantporosity <2%. Skeletal fragments of gastropodsare common, thin-shelled pelecypods are rare,green algae are very rare, and miliolids arecommon.

Hole392A Core 13 Cored Interval : 164.5-174.0 m

TIME

-ROC

KUN

IT(Indeterminate]

ZONE

FOSSILCHARACTER

FORA

MS

NANN

OS

RADS SECTION

CC

METE

RSJLL±

LITHOLOGY

SEDI

MENT

ARY

STRU

CTUR

ESDR

ILLI

NGDI

STUR

BANC

E 1

LITH

OLOG

YSA

MPLE

Carbon-Carbonate {%)

ççCaC03 99.0Org. C 0.0Total C 12.0


LIMESTONE

Entire recovery consisted of three pieces ofSKELETAL-FRAGMENT INTRACLASTIC LIME PACKSTONE,with miliolids, gastropods, and greenalgae as in Core 10, Sect. 2). Inter-particle, moldic and small-vug porosity whichis incompletely filled by two generations ofcement.

376

SITE 392

1

r~

-

-

_

-

-

-

-

-

—

-

-

-


2 3, . I .

5.53

>

4

I

m0 -

-

1 -

5.97

2 -

3 -

4 -

6 -

7 -

8 -

9—

Site 392A

SECTIONcm

- 2 5

- 5 0

V

- 7 5

t> gravimetric wet-bulk density- ^ parallel sonic velocity-{- perpendicular sonic velocity

Φ undifferentiated sonic velocity--••continuous GRAPE

11-1

377

SITE 392


8 _ ,, CHARACTER i g Hill

g | I £ S S E LITHOLOGY i t E i ! § ^ LITHOLOGIC DESCRIPTIONS i z ca ,Λ s: Q α > w h-stH o <: =c °° •2- U J µ - α : >-. >—••=c•~~ u_ z cü IΛWQQ-ICΛ

S c c

^ LIMESTONE

ë ° Entire recovery consisted of four smallSi pieces of PELLETOIDAL INTRACLASTIC PACKSTONE,-S very pale brown (10YR 8/3), with miliolids and^ a few gastropods.

Fenestral and tubular (burrows?) porositynearly filled with two generations of cementexcept where enhanced by vug formation.Remnant porosity is 0-2%.

Carbon-Carbonate {%)CC_



^ § o ^ S 5 £ LITHOLOGY ë t ^ = o ^ LITHOLOGIC DESCRIPTIONg cc z Q ^ ^ GQ:MWI-Σr o <t cc •*- LU h-o: i-< M <1 U _ ^ Q : IΛWDQ —loo

___ LIMESTONE<D

« - Recovery consisted of twelve pieces of rockI n K Z vmn including PELLETOIDAL INTRACLASTIC PACKSTONE,_ u.b _ vuiu

a f e w G R A I N S T ON E S - some of which are highly re-

-% I crystallized - and two pieces of crystalline•o I SKELETAL-FRAGMENT LIME WACKESTONE. The wacke-£, 1.0— stons has fine-scale moldic porosity which is

R _ _ Z ^ σ approximately 10% preserved and has very little- J ^ ^ r ‰ X ~

e 5Y 8/2 cement. Gastropods are common. One possible

I I I - ^ ^ > ^ . x

_ ' coral and an dascyclad green algaewhich is common.


1-123

CaCO 94.0Org. C 0.2Total C 11.5

378

SITE 392

1

r~

-

—

-

-

-

-

-

-

-

-

—


2 31 . I .

>

4

1

m0 -

1 -

-

2 -

*5 mm

4 -

5 -

6 -

7

8 -

9 -

Site 392ASECTION

- 2 5

- 5 0

- 7 5

- 1 0 0

- 1 2 5

^ 1 5 0

t> gravimetric wet-bulk density- ^ parallel sonic velocity-|- perpendicular sonic velocity

© undifferentiated sonic velocity-.-•-continuous GRAPE

15-1

379

SITE 392


FOSSILCHARACTER


0.5 —VOID

1.0- "10YR 7/2and10YR 8/2

LIMESTONE

Recovery consisted of several pieces of rockof the following types (listed in order ofabundance).

1) SKELETAL LIME PACKSTONE, mo!die porosity(5-10% preserved). Gastropods are common,many unidentified skeletal fragments includingdasyclad green algae in Core 15,core-catcher sample.

2) Very dense LIME MUDSTONE, probably re-crystallized "Type 1", but only a few microvugsare preserved. Porosity = <3%.

3) FENESTRAL PACKSTONE, extensive fenestralporosity ("Birdseye" porosity). Miliolids arecommon.

Basal 2 pieces are inter!ayered PELLETOIDAL-INTRACLASTIC LIME PACKSTONE and GRAINSTONE withextensive "birdseye" fenestral porosity whichis incompletely filled in upper piece.


CaC03Org. CTotal C

1-106

98.00.011.8


FOSSILCHARACTER

LITHOLOGY

LLJ I—u~> t / )


VOID

1.0--e

LIMESTONE

SKELETAL LIME PACKSTONE, white (10YR 8/2),porosity, with gastropods and

dasyclad green algae.

~v~

Interlaminated PELLETOIDAL-INTRACLASTIC LIMEPACKSTONE (muddy) and GRAINSTONE, laminated,fenestral porosity is extensively spar filled.

PELLETOIDAL INTRACLASTIC PACKSTONE, muddy,fenestrae poorly developed.

110 cm - Coral (?) fragment.

125 cm - Colonial coral in clast, extensivelyleached. Scraps of coral!ites, tubes ofborers (?) preserved in clear spar, theneroded and redeposited. Adjacent algae may beencrustor, but more ükely a neighbor.


1-81

CaC03Org. CTotal C

96.00.011.6

380

SITE 392

1

r~

—

-


2 3

, . |

6.21

> +

4

I

m0 -

1 -

-

2 -

3 -

Site 392A

SECTIONcm

- 0

1

r~

—

-

—

-

-


2 31 ' 1

>6.07

Θ

4

1

m0 -

-

1 -

2 -

3 -

- 2 5

- 5 0

- 7 5

-100

-125

—150

O gravimetric wet-bulk density- ^ parallel sonic velocity-|- perpendicular sonic velocity

© undifferentiated sonic velocity-*— continuous GRAPE

16-1 17-1

381

SITE 392

Hole 392A Core 18 Cored I n t e r v a l : 202.5-212.0 m

I I FOSSIL I I I L I Sig^ CHARACTER g ^ l^glgJS | £ g 5 § LITHOLOGY I t 5 l § ^ LITHOLOGIC DESCRIPTION2: o: 2: α Hd y QQ:M(ΛI-Σ!-• o <c <c *- w t - α " " <1— U - ^ D : I / H Λ D Q —100

% _CCJ j LIMESTONE

j| Recovery consisted of three pieces of MILIOLID£ PELLETOIDAL LIME GRAINSTONE/PACKSTONE with-ë "muddy" laminae and sparse fenestral porosity.,5 Possible superficial ooids in one piece.


FOSSIL I I P I ~

' o ε o h tif LITHOLOGY Σ O ^ = O ^ LITHOLOGIC DESCRIPTION^J => M <c z: u-> \f [– H - . — . J ^ Π I Q .g a: z α H ^ Q ^ M I Λ I - Σr o = t < c 0 0 LU 1— α:!—1 •—'<c1— u_ Z Q: OOOOQQ—100

0Z L I M E S T O N E

<S• " VOID^ I MILIOLID LIME WACKESTONE, very pale brownc j o; (10YR 8/3), with lenses of PELLETOIDAL PACK-•| 0 . 5 — i a j r r z j a i p ^ s . g STONE. Indist inct lamination of local ly spar-OJ i _ 1 , 1 , 1 jjbr / _ e ü- fi/. filled porosity - mainly fenestral with vertical-ë - j I {fl I , « ^ -lUTK D / ^ η c o n n e c t i o n s (burrows[?], gas vents [?], mud

p _ _ -I Q_T—-K- r I I co cracks [ ? ] ) . Fenestrae partly floored with

^ ' - •i—1 --t- ' i ^ r^ L f i n e white mud.I VOID S 7 o INTRACLASTIC PELLETOIDAL LIME GRAINSTONE,

^—-^ "~ very pale brown (10YR 7/3), coated grains.Matrix of M/2 mm pel letoids, m i l i o l i d s , androunded shell fragments with o o l i t i c skins.Intraclasts to 5 cm (mostly altered withthick coatings).

Porosity - incompletely f i l l e d (M%) shelterpores and small vugs. Original intergranularporosity f i l l e d with clear spar.

80-83 cm - Small coral fragments.

98-100 cm - Coated muddy packstone withgreen algae(?) in matrix. Gastropods,pelecypods, rare. Benthic foraminifers present.

Carbon-Carbonate(?)

1-72

CaC03 99.0Org. C 0.1T o t a l C 11.9

•j>

382

SITE 392


Site 392A

SECTION4 cm

1 ro

•25

- 5 0

- 7 5

- 1 0 0

- 1 2 5

0 gravimetric wet-bulk density- ^ parallel sonic velocity- j - perpendicular sonic velocity

© undifferentiated sonic velocity-^—continuous GRAPE

19-1

383

SITE 392


n i FOSSIL i i i M dg _ w CHARACTER g ggglg^ § £ g R E LITHOLOGY 8 t ? l § ^ LITHOLOGIC DESCRIPTION

=3 M g I g g g Sg^UFEè! -• o <c •=c °° * - lui-QiMhH<I— U_ Z Oi CO CO Q O ICO

- j • LIMESTONE+J ~

J I V 0 I D SKELETAL LIME PACKSTONE, extensively recrystal-1 - l ized, moldic porosity ( 5% preserved), gastro-

•S ~=F=^t-^A x ~ I T 1 0 Y R 8 / 2 p o d s ' m i l i ° 1 1 d s

1 ~ '®! L I JJ "" \ OOLITIC INTRACLASTIC L. GRAINSTONE, oo l i t ic-– ] Q_~T—| © \ ® ^ ^ \ coatings th in ; intraclasts are coated. Porosity

R — — - Q , ' » | I ^ . \ only in a few small vugs and largest shelter••~?jj~&" ' ^ J^ "^ ^ \ pores. Original intragranular porosity is

-:5llgli j ^ x b *> s×• o \ cement f i l l e d .

V_Horizontal sheet crack with gravity or pendantcement possibly along erosion surface.

Skeletal material includes green algae,mi l io l ids, benthic foraminifers, andbryazoa (encruster).

116-120 cm - muddier and/or recrystallizedvertical "bubble strings" or f i l l ed pores;gallened worm tubes.

140 cm - Large cylindrical mud tube.


1-61



FOSSIL I I I E~H~~Slg _ w

CHARACTER § ^ Hill^ S § ^ g g £ LITHOLOGY i t ^ = o ^ LITHOLOGIC DESCRIPTION^ ^ M 2 I § g g S^dto^è•~1 O <C < t ^ "*- UJ|—Oi l—i i—.<cI— U _ Z Q ; O O C O Q Q ioo

0 I— . LIMESTONE

5 I VOID y~ööllJE LIME GRAINSTONE, very pale brown2 - x / CjOYR 7/3) with abundant in t rac las ts and/or•p 0.5— / l i t hoc las t s . Porosity f i l l e d by three or| 1 - _ _ / more cement generations. Fossils include% - lál<σ>t _ | = i i ^ TJJ- " ^ " cl numerous green algae, and foraminifers"i 1 n _ I { Jlg( I ^ ^ (rare). Sheet cracks, shelter pores andd R _ _ ' - ^ r 5 ^ '."^ \ ~ e ^ coarse/fine layering present. ErosionaH?)

Z\ ' |A.^—^~ ^ °~\ surfaces between 90-95 cm, well-cemented_ 3 pi j T—{ ^ 'ö^~ ^ >v ooid grainstone at 75 cm.

\

MILIOLID WACKESTONE, microcrys ta l l ine , withnumerous f i l l e d microvugs, also burrowsf i l l e d with ooids, in t rac las ts and raresu r f i c i a l ooids. Few foraminifers (other thanmi l i o l i ds ) and many green algae. Erosionsurfaces (?) between 145-150 cm.tween 145-150 cm.


1-114

CaC03 100.0Org. C 0.1Total C 12.0

384

SITE 392


2 3

Site 392A

I

SECTION4 cm

π i-o

mO-i

1-1

2 - 1

3 -

4 -

1

I

—

-

-

-


2

T

>

3

I

5.96

Θ

4

I

m0 -

1 —

2 -

3 -

- 2 5

- 5 0

- 7 5

- 1 0 0

-125

- 1 5 0

f> gravimetric wet-bulk density

- ^ parallel sonic velocity

-J- perpendicular sonic velocity

© undifferentiated sonic velocity-^-continuous GRAPE

20-1 21-1

385

SITE 392


" I I FOSSIL I I I LI -Ig , m IHARACTE! § <|ggg2 1 1 Σ o ^ H ui LITH0L0GY ë t ^ = o ^ LITH0L0GIC DESCRIPTION

,1-1 O • = t • < 0 0 - 2 1 - UJ I— CO— i-i<CI— LLZQ; OOOOQQ —ICΛ

LIMESTONE

« I /TNTRACLASTIC OOLITE LIME GRAINSTONE, very pale•5= - / brown (10YR8/3), large skeletal component| 0.5— <_ / (mainly ooid nucle i ) , shelter pores which are-£ ] - °°_/ f i l l e d with two qenerations of cement. Fossils-S Z L 1 /=!^pà? go- ** include mi l io l ids and other foraminifers,M 1 n_I (?),' <fli J*yi j - ^ ^ _ IB gastropods, pelecypods, green algae, and coral

n _ _ * - ' i ' i ' -~2 C ~ (?) fragments. Erosional surfaces(?) between~ ' • ' • ^ n j ; " \ ^ 80 and 95 cm.

^^v \ . 94-112 cm - "Super-oolite" with multiple° \ \ clear r ings, coarse and fine layering,

\ \ some wackestone laminae.

\ SKELETAL LIME PACKSTONE, very pale brown\ (10YR 8/3) muddy, f ine-grained, with abundant\ m i l i o l i ds , gastropods, and green algae\ (abundant 120-133 cm). Small vugs incompletely\ f i l l e d with spar and f i l l e d shelter pores and\ fenestrae (esp. 137-142 cm).


1-104

CaC03 98.0Org. C 0.1T o t a i C ~11-8


FOSSIL I k I yl

^ 1 ^ g g £ LITHOLOGY i t S I S ^ LITHOLOGIC DESCRIPTION

o <: • c °° * - LU 1— Q; W I-I<CI— Ü_ Z Q; i^wαα-iw

_ 2 Z LIMESTONE

-Sj ~ Recovery consisted of rock pieces of twoc _ l ithologic types:

I 0<5

~α> , 1) SKELETAL LIME PACKSTONE(?), badly recrystal-

^ ^ lized? moldic porosity 5%-l5%; intergranular

= , Q^ —, porosity is solution enlarged to 5%. Fossils

£* R — — --|@r ' i5^ "^ include gastropods, pelecypods, miliolids and

~-}_-' I 'Q| \ _e other foraminifers.

I I I I I I -fr", ' ! q 1 ^ 1 2) OOLITE LIME GRAINSTONE, with shelter pores.


1-132CaC0

3 99.0

Org. C 0.0Total C 12.0(Pieces were mixed when they fell out of theliner on board ship; no stratigraphicsequence is preserved).

386

SITE 392

1

r

-

-

-


2 3

1 ' 1

>5.99

G

4

1

m0 -

2 -

Site 392A

SECTIONcm

1-0

- 2 5

1

r~1

-

-

-

-

-

DENSITY (gm/cc)

SONIC VELOCITY (km/sec)

2 3

I ' | '

t>

4

I

m0 -

4.73

Θ

1 -

2 -

3 -

4 -

- 5 0

— 75

- 1 0 0

- 1 2 5

- 1 5 0

[> gravimetric wet-bulk density-& parallel sonic velocity-|- perpendicular sonic velocity

© undifferentiated sonic velocity

-.—continuous GRAPE22-1 23-1

387

SITE 392


FOSSILCHARACTER


cc LIMESTONE

Recovery consisted of nine loose pieces(recovered in the core-catcher) of twolithologic types with several diageneticvariants.1) (Dominant lithology) - SKELETAL PELLETOIDALLIME GRAINSTONE WITH INTRACLASTS, porositytypes are:

a) Skeletal moldic with some vug enlargementof molds and (?) primary inter- and intragranularpores. Porosity is 2%-l%, ave. 4%.

b) Milky druse-filled vugs comprising about5% of the rock.

Fossils include miliolids (abundant), and otherbenthic foraminifers, gastropods, green algae,pelecypods and one cemented mudworm tube (5 mmdiam.).

2) INTRACLAST-OOLITE GRAINSTONE, generallynonporous, one piece appears to preserve amicrokarst surface filled with mud and clasts.Alteration shows that laminated oolite isnot simply mechanical erosion, but also chemicalalteration in slightly lithified rock.


81-rv i_<i z:LU rD

1—

(Ind

eter

mina

te)

ZONE

FOSSILCHARACTER

FORA

MS

NANN

OS

RADS

Carbon-Carbonate (

SECTION

CC

0çç.


METE

RSl l

l

LITHOLOGY

SEDI

MENT

ARY

1ST

RUCT

URES

1

aw

DRIL

LING

DIST

URBA

NCE!

X

LITH

OLOG

YSA

MPLE

- f.


LIMESTONE

Entire recovery consisted of six rock pieces offour lithologic types:

1) FORAMINIFER PELLETOIDAL GRAINSTONE, white(10YR 8/2), surficial ooids are common, muddyclasts in one piece. Pores (burrow, shelter andmolds) are filled.

2) GASTROPOD PELLETOIDAL WACKESTONE, very palebrown (10YR 7/3), grainstone fills burrows inone piece which is highly recrystallized.Porosity (moldic gastropods) is 2% in onepiece. Other piece has two generations ofcement which fills extensive sheet crack andvug network.

3) PELLETOIDAL INTRACLASTIC PACKSTONE, withtwo generations of cement which fill vugsand fenestrae.

4) MILIOLID INTRACLASTIC WACKESTONE, withPACKSTONE lenses, laminated, surficial ooidsare common. Extensive spar-filled fenestralporosity. Three laminae (one cemented?) ofGRAINSTONE with miliolids and surficial ooids,possibly graded(?).

388

SITE 392

HoleTI

ME-R

OCK

UNIT

(Ind

eter

mina

te)

392A

ZONE

Core 26

FCHA

oo

<C

oLL.

R

OSS

RAC1

00o1Z.

<C

LTER

ooQ<Ccc

SECT

ION

0

1ME

TERS

0.5-

λ n

Cored Interval:

LITHOLOGY

SEDI

MENT

ARY

STRU

CTUR

ES

P,

DRIL

LING

DIST

URBA

NCE

\/\

278.5-288.0 m

LITH

OLOG

YSA

MPLE

e


LIMESTONE

MICRITIC LIMESTONE, white (10YR 8/2),partially to highly recrystaliized, frag-mented.

100-102 cm - crystalline SKELETAL-FRAGMENT-~ PELLETOIDAL LIMESTONE, original texture

obscured, moidic porosity - l%-3% with sub-ordinant small vugs. Contains pelecypod

° fragments, gastropods, milioiids and otherforaminifers.

111-113 cm - crystalline laminated INTRA-CLASTIC FENESTRAL LIMESTONE, 3% fenestralporosity.

122-130 cm - INTRACLASTIC FENESTRAL LIMEPACKSTONE, some pelletoids, crystallinedasyclad green algae abundant, vug-enlarged fenestral porosity, 4-20%.

130-143 cm - OOLITIC INTRACLASTIC LIMEGRAINSTONE, primary intergranular andshelter porosity, slightly solution en-larged vugs. Dasycl ad green algaeis abundant; gastropods are rare.

143-150 cm - SKELETAL FRAGMENT LIMESTONE,

crystalline, mo!die porosity l%-2%.


1-100

CaCO3 99.0



1 TI

ME-R

OCK

UNIT

(Ind

eter

mina

te)

ZONE

FOSSILCHARACTER

FORA

MS

NANN

OS

RADS SECT

ION

CC

METE

RS

LITHOLOGY

SEDI

MENT

ARY

STRU

CTUR

ESDR

ILLI

NGDI

STUR

BANC

E!LI

THOL

OGY

SAMP

LE LITHOLOGIC DESCRIPTION

LIMESTONE

Recovery consisted of five pieces of rock ofthree lithologic types:

1) PELLETOIDAL-INTRACLASTIC LIME PACKSTONE,with spar-filled fenestral and shelterporosity (max. 3% preserved). Contains foram-inifers and green algae.

2) CRYSTALLINE LIMESTONE, pelletoids, foram-inifers and skeletal molds and spar-filled tubes.Porosity 40%, vugs to 2 cm, spar-lined molds,small, spar-lined fossils.

3) OOLITIC INTRACLASTIC GRAINSTONE inter!ayer

(graded?) in PELL-INTRACLASTIC LS. (PACKSTONE?)

with spar-filled fenestrae and skeletal molds.


CaCO3 100.0


390

SITE 392

1

r~

-

-

-

-

-

-

-

-

-

-


2 3

1 . I .

4

1

m0 -

1 -

2 -

3 -

4 -

-

6 -

7 -

p

9 -

Site 392ASECTION

- 2 5

- 5 0

- 7 5

- 1 0 0

- 1 2 5

> gravimetric wet-bulk density- ^ parallel sonic velocity- j - perpendicular sonic velocity

© undifferentiated sonic velocity--—continuous GRAPE

26-1

391

SITE 392


FOSSILCHARACTER

LITHOLOGYICQ.t— :


cc liJ LIMESTONE

Eighteen pieces of three lithologic typeswere recovered:

1) CRYSTALLINE PELLETOIDAL - SKELETAL LIME-STONE (probably GRAINSTONE) (11 pieces), white(N9), micritic texture, moldic porosity (<3%),some solution enlarged and possibly inter-granular pores result in porsities to 20%.Fossils include gastropods, foraminifers,branching coral (?) several tiny ammonites.2) MILIOLID PELLETOIDAL WACKESTONE (4 pieces)with few small vugs. Maximum porosity is 5%.One piece with thin packstone laminae, fenestraland burrow porosity, solution enlarged, nowfilled with sparry calcite.3) OOLITJC-INTRACLASTIC LIME GRAINSTONES (3pieces) with surficial oolites and solutionenlarged but generally spar-filled fenestraland shelter porosity. Porosity =21


TIME

-ROC

KUN

IT(I

ndet

ermi

nate

)

ZONE

FOSSILCHARACTER

FORA

MS

NANN

OS

RADS SECTION

JLC_

METE

RSl

l l

LITHOLOGY

I SE

DIME

NTAR

Y 1

1 ST

RUCT

URES

1

DRIL

LING

DIST

URBA

NCE!

LITH

OLOG

YSA

MPLE LITHOLOGIC DESCRIPTION

LIMESTONE

Recovery consisted of four pieces of rockcomprising two lithologies:

1) OOLITIC-INTRACLASTIC LIME GRAINSTONE,(with surficial oolites) miliolids anddasyclad green algae, laminated.2) MILIOLID WACKESTONE AND MILIOLID PELLETOIDALLIME GRAINSTONE, with calcite-filled fenestralporosity. Contains miliolids, gastropod moldand dasyclad green algae, indistinctlylaminated.

392


g _ w CHARACTER g llilgf S § £ o P § LITH0L0GY I t S l o j LITHOLOGIC DESCRIPTION

•~ o <c <c ° ° ^• LU i— en i-i >-(<;I— u _ ^ o i IΛIΛQQ ico

« CC I J LIMESTONE

^ Recovery consisted of six pieces of LIMESTONE

•£ comprising three lithologies:-a

S, 1) MILIOLID PELLETOIDAL LIME GRAINSTONE withfossil fragments including dasyclad greenalgae, small vugs and enlarged molds;proosity ^5%.2) INTRACLASTIC SKELETAL FRAGMENT LIME WACKE-STONE, with shelter porosity (porosity %2%)dasyclad green algae(?) is common,miliolids rare.

3) CRYSTALLINE SKELETAL LIMESTONE, with net-work of irregular cellular calcite suggestiveof branching porous coral (max. diam. ^1 cm).(A similar form present in Core 28, core-catcher sample.)


FOSSIL I I E~T~yl

^ ^ o Σ O h ti LITHOLOGY Σ & ^ = O ^ LITHOLOGIC DESCRIPTION

> o <c <c °° s UI-O:I-IM<1— L ± - Z Q ; 0 O C O C 3 Q lOO

§ ~ ~ cc -SaeaQ—l××r ε LIMESTONE

g Recovery consisted of nine pieces of LIMESTONE

"£ of four lithologic types:-σ

£ | | 1) CRYSTALLINE SKELETAL FRAGMENT LIME PACK-STONE, with molds and small vugs (mostlyfilled), porosity 0%-4%, gastropods andforaminifers are common, intraclasts, rare.2) SKELETAL INTRACLASTIC LIME PACKSTONE.

3) INTERLAMINATED INTRACLASTIC SKELETAL LIMEWACKESTONE AND PACKSTONE, with spar-filledburrow and fenestral porosity. Foraminifers,dasyclad green algae), intraclasts andpelletoids.

4) LAYERED MUDSTONE, unfossiliferous,fenestrae and burrows or gas vents aresolution enlarged, then filled with secondgeneration cement.


çç_CaC03 100.0Org. C 0.1Total C 12.0

There was no recovery in Cores 32 and 33.

6. site 392: south rim of blake nose - deep sea drilling · 2007. 5. 10. · site 392, situated on...

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