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www.sciencemag.org/cgi/content/full/336/6089/1693/DC1

Supplementary Materials for

Bilaterian Burrows and Grazing Behavior at >585 Million Years Ago

ErnestoPecoits,* Kurt O.Konhauser, Natalie R.Aubet, Larry M.Heaman, GerardoVeroslavsky, Richard A.Stern, Murray K.Gingras

*To whom correspondence should be addressed. E-mail: [email protected]

Published 29 June 2012, Science336, 1693 (2012)

DOI: 10.1126/science.1216295

This PDF file includes:

Materials and Methods

Supplementary Text

Figs. S1 to S13

Tables S1 to S4

References (3146)


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Materials and Methods

U-Pb Geochronology

U-Pb zircon analyses were conducted on four rock samples; two granite samples

080105/3 and S1086 (alias 100110/2), sandstone 07122/3, and siltstone Tacuar-1-2011.

The samples were pulverized to a fine powder using a jaw crusher and Bico disk mill,while zircon concentrates were obtained using a combination of density (Wilfley Table,

Methylene Iodide Heavy Liquid) and magnetic (Frantz Isodynamic Separator)techniques. Individual zircon crystals were hand selected for analysis using a binocular

microscope and CL imaging performed on select grains. Multiple U-Pb techniques were

applied to each sample and the following outlines the procedures used. Age calculationswere performed using Isoplot (31) and age uncertainties are reported at two sigma. The

uranium decay constants and 238U/235U value used in this study are those recommended

by Jaffey et al. (32).

Laser Ablation Multi-Collector Inductively Coupled Plasma Mass Spectrometry (LA-

MC-ICPMS)Laser ablation MC-ICPMS U-Pb dating was conducted in two modes; in situ

analyses were performed on multiple thin sections of granite 080105/3 and detrital zirconcrystals were hand-selected from a zircon concentrate prepared from the sedimentary

samples, secured in an epoxy mount, and polished to expose the interior of the crystals.

The U-Pb analyses were performed with a Nu Plasma multi-collector ICPMS equippedwith 12 Faraday detectors and 3 ion counter detectors. The zircons were ablated with a

213nm New Wave laser and typical analysis spots were 40 microns in diameter. The

grain mount zircon analyses reported in the Tables S3 and S4 were not corrected for thepresence of common lead. Two zircon standards were analyzed with each sample, a

Proterozoic zircon (LH94-15) was used to monitor U/Pb fractionation and a

Neoproterozoic zircon (GJ-1;

206

Pb/

238

U ID-TIMS date of 605.4 0.6 Ma; Heaman,unpublished data) was run as a blind standard to evaluate accuracy of the method. Duringthe two laser ablation sessions on grain mounts the average 206Pb/238U date obtained for

GJ-1 zircon was 611.6 8.6 Ma (n=5) and 606.8 9.2 Ma (n=8), both results are within

error of the ID-TIMS value. Details of the U-Pb LA-MC-ICPMS technique used at theUniversity of Alberta are outlined in Simonetti et al. (33-34).

Sensitive High Resolution Ion Microprobe (SHRIMP)

A zircon grain mount (CCIM #M1014), which included unknown granite sample,S1086, TEM2 standard zircon (reference age 416.8 Ma) (35), and 6266 standard zircon

(reference age 559 Ma; 36), was prepared as above, and ground and polished with

diamond suspensions. A scanning electron microscope (Zeiss EVO 15), equipped with a

Gatan ChromaCL system, was used to characterize internal growth zones prior toanalysis. Subsequently, the zircons were analyzed using the SHRIMP IIE ion microprobe

at Geoscience Australia, Canberra using standard methods and conditions, i.e., primary:

10 keV O2-, ~20 m diameter; secondary: mass resolution ~5000, and sequential

detection by electron multiplier of 10 peaks between 196Zr20+ and 270UO2

+. The TEM2

zircon was analyzed after every 4 unknowns, and was used to calibrate the206

Pb/238

U

ages and to determine the associated calibration uncertainty. The U-Pb data were


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processed using the SQUID2 application (37), utilizing206

Pb+/

270UO2

+(one dimensional

calibration (after 36) to calibrate206

Pb/238

U, and204

Pb for common Pb correction. ThePb-isotope ratios were assumed to be free of bias associated with instrumental mass

fractionation. The weighted mean206

Pb/238

U age of 6266 zircon (N=8), analyzed to

estimate accuracy, determined during this work was 5594 Ma (MSWD = 0.46), identical

to the independent reference value. Further details of the SHRIMP experimentaltechnique used in this study can be found in Stern et al. (38).

Isotope Dilution Thermal Ionization Mass Spectrometry (ID-TIMS)

U-Pb zircon ID-TIMS analyses were conducted on two samples; granite 080105/3

and three zircon crystals from were extracted from the mount containing detrital zirconsisolated from sandstone Tacuar-1-2011 to verify the accuracy of the youngest grains

identified. The zircon fractions prepared for ID-TIMS were cleaned in acid prior to

dissolution, weighed using an ultra-microbalance, and dissolved in TFE Teflon digestion

vessels in a mixture of HF/HNO3 together with a measured amount of205

Pb/235

U tracer

solution. The samples were heated to ~200

o

C for ~100 hours and for most fractions Uand Pb were purified using anion exchange chromatography. Chromatography was not

conducted on single zircon grain #52 from sample Tacuar-1-2011 because of its smallsize (


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burrow morphology and preservation are illustrated in Fig. S10. The slabs also show the

absence of any inorganic sedimentary features that mimic trace fossils in this bed.Permian sedimentary rocks (Tres Islas Formation), prominent in the northwest part

of the area, are flat-lying and undisturbed (42-44), and rest unconformably on the older

rocks including the Tacuar Fm, the granite and mylonites (see for example 41) (Fig. S2).

In the area, the Tres Islas Fm comprises fluvio-deltaic sandstones that are intercalatedwith massive and bedded mudstones (cf. 43, 45). These sandstones contain abundant

silicified wood fragments (Glossopteris flora), and the mudstones host more than 40

species of pollen and spores of early Permian age (46and references therein).Mylonitic rocks consist of ductilely deformed granitoids and are found throughout

the area but most commonly in the central part. Similarly, good exposures of the intrusive

granite are present within the mapped area but a larger part of the batholith extendstowards the southwest and northeast. Pre-batholithic rocks, represented by the Tacuar

Fm and mylonites, show the effects of considerable deformation. In the former, cleavage

generally extends directly to the igneous contacts where they are abruptly truncated near

shear corridors, which represent late reactivations of the mylonitic shear zone.

In some locations there exist cross-cutting relationships (i.e., discordant contacts)with abundant folds and faults that provide evidence of the batholiths intrusion (Fig. S3).

Local features of the granite contact zone indicate thermal interaction with country rocks(contact metamorphism) and removal/stoping of material by magma intrusion (xenoliths).

Therefore, locally discordant contacts, contact metamorphism and abundant xenoliths

strongly support an intrusive relationship of the granite into the Tacuar Fm.

Contact relationshipsStructural evidence:

The granite is discordant with the sedimentary strata (see next section below) and

schistosity of the Tacuar Fm, and with the foliation of the mylonites. Furthermore, as a

result of the intrusion the granite caused local deformation in the country rocks near itscontact.

A significant part of the Tacuar Fm has been affected by a shear zone, which

produced a shear-associated schistosity. Closer to the shear, the schistosity isprogressively better developed and forms thicker tabular zones that take on a mylonitic

appearance suggesting that shear-strain intensity increases towards the shear zone. In the

same outcrop, the granite intruding the rhythmites of the Tacuar Fm shows no evidenceof being affected by shearing. This suggests that the intrusion occurred after the shear

event that foliated the Tacuar Fm (Figs. S4A and B).

The main structures generated in the Tacuar Fm during intrusion are folds, which

are concentrated near the pluton margins. Within 5-100 m of this contact these folds

grade into low-angle dipping rocks indicating that the termination of the structures issmooth and progressive, as they decrease in wavelength and amplitude (Fig. S4C).

Thermal interaction between granite and host rock:

The granite intrusion is characterized by the presence of chilled margins, bleaching,silicification, hematitization and occasional quartz-bearing cavities (Figs. S5-S8).

Pervasive silicification and hematitization within metasomatized contact zones between


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sedimentary strata and the granite are attributed to the hot fluids percolating at the contact

with the granite intrusion. The silicified portion is also characterized by the moreabundant cavities and vugs filled with quartz. Silicified rocks crop out as layers of several

centimetres to 4 meters in thickness and exhibit either sharp or irregular contact with the

intrusive granite but a gradational contact with adjacent sedimentary strata. The altered

rocks are bleached to a pale grey-cream colour and their texture and sedimentarystructures (e.g., laminae) have been obliterated. These changes occur gradually within a

550 cm thick zone, although locally they were observed up to 2 m from the contact.

Xenoliths:The granite forms a dome-shaped intrusion, and near contacts, it contains xenoliths

of the Tacuar Fm strata (Fig. S9). Within the central area of the Tacuar Fm exposures,

where the contact with the granite is steep, small (1-20 cm) xenoliths of mudstone are

common. The site shows numerous metamorphosed, and occasionally partially melted,disc- and blade-shaped, centimetre-size xenoliths that consist of rhythmites that were

derived from the Tacuar Fm. Xenoliths from the basement mylonites have not been

observed.

U-Pb Results

Granite (080105/3 and S1086):

Two samples from the granite that intrudes the Tacuar Fm were investigated in this

study. The first sample 080105/3 was collected near the contact (within a meter) and thesecond sample S1086 was collected some distance away (ca. 8 meters) from the contact.

In both samples the recovered zircons consist of colourless prismatic grains with aspect

ratios that vary between 2:1 and 4:1. This granite intrudes the fossil-bearing unit andtherefore its age is pivotal in constraining a minimum depositional age for this stratum.

Three U-Pb zircon dating techniques were applied. For sample 080105/3, both LA-MC-

ICPMS and ID-TIMS techniques were applied and the results are presented in Tables S1

and S2, respectively. A total of 20 in situ LA-MC-ICPMS U-Pb spot analyses on 16zircon grains identified in multiple thin sections of granite 080105/3 are reported in Table

S1. Ten of these analyses are >10% discordant and many of these have older207

Pb/206

Pb

dates, indicating the presence of zircon inheritance in this zircon population (as old as 2.5Ga, Table S1). The ten least discordant analyses (i.e.,


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analysis indicates well-preserved oscillatory zoning (Fig. S13), the outer regions of which

were specifically targeted for analysis.The SHRIMP U-Pb results are presented in Table S1. The analysis of spot 11.1 has

inaccurate207

Pb/206

Pb (and discordance) due to problems with207

Pb centering, but the

other isotopic measurements remain valid. The weighted average206

Pb/238

U date for all

20 analyses is 584 4 Ma and is indistinguishable from the LA-MC-ICPMS results forsample 080105/3. A concordia diagram displaying the 10 least discordant ICPMS

analyses from 080105/3 and the 20 SHRIMP analyses from S1086 are shown in Fig. 1

and together these data yield a very precise206

Pb/238

U date 585.0 3.3 Ma(MSWD=0.72), which we interpret as a robust minimum constraint for the emplacement

age of this granite. This age overlaps within error the weighted average207

Pb/206

Pb date

of 593 12 Ma calculated for ten least discordant LA-MC-ICPMS analyses.

Sedimentary Samples (Tacuar-1-2011 and 071220/3):Two sedimentary samples were investigated to compare the detrital zircon

provenance age distribution in the trace fossil bearing siltstone (Tacuar-1-2011) and a

second sandstone sample from the Permian Tres Islas Fm that overlies the Tacuar Fm. Atotal of approximately 100 detrital zircons were recovered from the fossil-bearing sample

Tacuar-1-2011; many of these grains are colourless to pink, 20 to 60 microns in the

longest dimension, subrounded prismatic forms with 3:1 to 4:1 aspect ratios. A small

number of grains were greater than 60 microns (e.g., #7, 27 and 49) and for many ofthese grains multiple spot analyses were attempted. The LA-MC-ICPMS U-Pb results for

52 zircon grains from this sample are presented in Table S3 (a number of the grains were

too small to analyze with a 40 micron diameter spot) and shown on a probability densityplot in Fig. S12C. The main zircon age mode in this sample occurs at 805.1 6.1 Ma

(n=6) with the youngest mode at 600.1 8.5 Ma (n=4). The youngest detrital zircons in

this sample constrain the depositional age of the Tacuar fossil-bearing unit to younger

than 600 Ma and older than 585 Ma, the minimum age determined for the cross-cuttinggranite.

A feature of the detrital zircon U-Pb results in this sample is that many analyses are

discordant (Table S3). Therefore, in an attempt to verify the accuracy of these data weextracted three crystals for ID-TIMS analyses (grains #35, 48 and 52). We were unable to

obtain ID-TIMS data for grain #35 (too small) but the results for the other two grains are

presented in Table S2. The U-Pb results for these two grains by both techniques are inexcellent agreement; for example compare the 207Pb/206Pbresults for 52B in Table S3

(600 15 Ma) with 52 in Table S2 (612 17 Ma).

The U-Pb LA-MC-ICPMS results for 194 zircon grains from nearby sandstone

sample 071120/3 are provided for comparison (Table S4) and displayed on probability

density plots (Figs. S12A, B). Detrital zircon grains in this sample are generally of betterquality (fewer fractures, less alteration etc.), slightly rounded, colourless prismatic forms

with a range of aspect ratios (3:1 to 8:1). Unlike the Tacuar fossil-bearing unit, this

Phanerozoic sandstone sample contains a large proportion of zircon detritus with207Pb/206Pb dates younger than 600 Ma. The youngest U-Pb zircon age mode occurs at

533.1 4.6 Ma (n=14) and provides a maximum age constraint for the deposition of the

strata immediately overlaying the Tacuar in this area.


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Fig. S1.

(A) Geological map of the type area of the Tacuar Fm near Melo, Uruguay showing thelocation of the fossil sites (A-E). Coordinates of the center of the map: 32 29 35 S, 5407 55. (B) Simplified cross-section through the type area of the Tacuar Fm illustrating

the geological relationships between the Sierra Ballena Shear System, granite intrusionand cover rocks. The geology shown in the NW-SE cross-section is best interpreted as a


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result of six major events: (1) A large (?)Palaeoproterozoic granite that now represents

the basement was emplaced. (2) This basement was then affected by the NE-SW trendingSierra Ballena Shear Zone. This shear system, which is more than 1200 km long and 3-6

km wide, generated mylonites and ultramylonites. (3) Diamictites, sandstones and

siltstone/shale rhythmites (i.e., the Tacuar Fm) were deposited. (4) Faulting and

cataclasis in the reactivated shear zone overprinted the sedimentary fabric of the TacuarFm generating multi-directional tilting of the strata, a local fracture cleavage and narrow

brittle shear corridors. (5) A diapiric granite dated to 585 3 Ma intruded the

surrounding country rocks and as a result of intrusion caused local deformation andcontact metamorphism in Tacuar Fm near the pluton contact. (6) The Permian Tres Islas

Fm was unconformably deposited on top of the Paleo/Mesoproterozoic basement, the

Tacuar Fm and the intrusive granite.


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Fig. S2.

Examples of the angular unconformity illustrated in Fig. S1B. The unconformity iscommonly observed along the NE-SW trending contact between the Tacuar and Tres

Islas formations. (A) Northward-plunging syncline of the Tacuar strata that are

unconformably overlain by Permian sandstones of the Tres Islas Fm. (B) Flat-lying strata

(red arrows) of the Tres Islas Fm (see location in A). (C) Dipping strata of the TacuarFm at fossil site D. At this location the angular unconformity is approximately 40. (D)

Close-up view of that indicated in Fig. C showing Tres Islas strata resting horizontally.


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Fig. S3.

Images from trace-fossil locality B (see Fig. S1A) that show the Tacuari-granite contact.The contact between the granite and the Tacuar Fm is traced in red. (A) General view of

the outcrop. Notice the antiform along the granite contact and the clear crosscutting (i.e.,discordant) relationship on the right limb. (B) Detail of the right limb dipping 45-50 E

and being intruded by the granite at 70-80 E (see location of picture in Fig. A). (C)Close-up view of Fig. B showing a sandstone layer and the trace-fossil bearing

rhythmites (see Figs. E and F). The inset shows the discordance between the granite and

sandstone, which has undergone a strong ferruginization. (D) Close-up view of Fig. Cshowing deeply silicified rhythmites immediately overlying the ferruginized sandstone

layer (see location of picture in Fig. C). (E) Location of trace fossils at site B. The trace


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fossils are located in the rhythmites approximately at 1 m from the contact with the

granite (see location of picture in Fig. C). (F) At this site, the rhythmites are only slightlysilicified and the trace fossils are well preserved. (a), (b), (c) and (d) correspond to the

fossil bearing slabs shown in Fig. E.


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Fig. S4.

Relationship between foliation, faulting and folding in the Tacuar Fm and the granite.

(A) Multiple 60 cm-spaced faults F cut across the previously existing cleavage Sn andshear corridors generated through reactivation of the northeast-striking Sierra Ballena

Shear Zone. (B) The foliation and fractures are truncated by the intrusive granite, which


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is devoid of any evidence of deformation (i.e., cleavage). Notice the chill margin at the

top of the granite likely formed by rapid cooling and characterized by a reduction incrystal size and a more reddish colour (contact between the granite and the Tacuar Fm

arrowed). (C) Macroscale example of parasitic folds on steep NE facing limb. These

folded rocks are located right below the angular unconformity (Fig. S1A; SW of point D)

and within the trace-fossil bearing rhythmites. Deformation is strong in this area and it isconfined mainly to the production of small-scale but tight folds. The relationships

observed between folds and the granite at the pluton margin strongly suggest that folding

was synchronous with intrusion of the granite (see also Fig. S3).


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Fig. S5.

Well-exposed outcrop showing multiple intrusive features of the granite into the Tacuarrhythmites. (A) General view of the outcrop. Notice the irregular nature of the contact

and the deformation (concave-upwards) produced by the intrusion. The contact between

the granite and the Tacuar Fm is traced in red. (B) Close-up view (see Fig. A) of the


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discordant contact between the granite and rhythmites. (C) Detail of Fig. B showing a

very well defined contact oriented perpendicular to sedimentary strata. (D) Detail of Fig.B showing ductile deformation located in the ductile (thermally weakened) aureole. (E)

Close-up view (see Fig. A) of the intrusive contact (arrowed) discordant to the

sedimentary layering.


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Fig. S6.Contact metamorphic effects of the granite intrusion on the Tacuar strata. (A) and (B)

Pervasive silicification is irregular in the country rock adjacent to the granite contact but

can be very pronounced generating vitric masses characterized by conchoidal fracture.

(C) and (D) Silica-filled cavities within the rhythmites preferentially developed along the

contact (see also Fig. S5C). (E) and (F) Country rock alteration also includes

hematization (greyish areas around cavities).


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Fig. S7.

Examples of silicification and bleaching on Tacuar Fm by contact metamorphism. (A)Rhythmites with faint lamination due to pervasive silicification. In (B) and (C)sedimentary lamination has been obliterated entirely and the rocks have been totally

decolorized by silicification. Notice the irregular nature of the contact between the

granite and the Tacuar Fm. (D), (E) and (F) show more examples of granite-country rockinteraction. Notice that all of the images indicate strong ferruginization along the

intrusive contact, which followed bleaching produced by silicification, and the partial

inclusion of the country rocks (black arrows).


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Fig. S8.

Contact relations between the intrusive granite and rhythmites of the Tacuar Fm (A), (C)and (E) show detailed views of the cross-cutting relationships between the granite and therhythmites (So: bedding). In all the cases, extensive silicification produced by contact

metamorphism (note also the sacaroid texture in E) make the rhythmites very resistant to

erosion. (B), (D) and (F) Microphotographs of the contacts shown in A, C and Eillustrating the discordant contacts with adjacent rhythmites and development of chilled

margins.


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Fig. S9.

Tacuar xenoliths within the intrusive granite. The xenoliths occur as tabular or rough-edged bodies that range from


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Fig. S10.

(A) Counterpart to the example depicted in Fig. 2A. Circular pits, in this slab and theothers that follow, represent impressions of small glacial dropstones on the bedding

surface. Two sinuous crossing burrows (top) and one curved burrow (bottom left) exhibit

prominent flanking levees and local preservation of beaded backfill (see especially Fig.

2A inset). These views are interpreted as the soles of infaunal burrows. Notice the burrowin the upper left leaving the bedding plane and then returning to it along the same path

(black arrow), with ovate burrow cross-sections at the points of exit and entry. (B) Two

slightly sinuous crossing burrows with prominent levees (bottom right) are interpreted asrepresenting the bottom-view of infaunal burrows. Near the middle of the sample are two

cross-cutting burrows showing collapse features interpreted as representing the top-view

of infaunal burrows. Burrow sinuosity and diameter are similar in both preservationalmodes. Epirelief counterparts (C) and (D) corresponding to Fig. 2B. Central burrow

showing irregular collapse features on top (most easily seen in the hyporelief) are

interpreted as representing the top-view of intrastratal burrows. Burrows on the left and

right exhibit beaded backfill and flanking levees and are interpreted as representing cross-

sections near the bottoms of burrows and are, therefore, more evident in the basal slab(D). Burrow sinuosity and diameter are similar in both preservational modes. (E)

Concave epirelief preservation of the complete slab containing Fig. 2F. The prominent,bilobate burrow shows beaded backfill and locally distinct levees (interpreted as

representing a cross-section near the bottom of an infaunal burrow) intersecting,

following, then diverging from an older burrow that exhibits poorly developed lateral

levees along its length (interpreted as representing a slightly undulose burrow moving upand down with respect to the plane of preservation shown). Also present is a poorly

preserved (undertrack or overtrack) burrow with irregular collapse features on top (upper

centre) and a burrow represented by a ridge with flanking levees (top right). Note that allthree preservational grades of burrows on this slab show similar sinuosity and burrow

diameter. (F) Several curved burrows show bilobate lower surfaces. Note that the

burrows continue undisturbed beneath unburrowed lamination, indicating that they are

not later penetrative surface features imposed on the bed. (G) Two burrows, with right-hand burrow passing from unilobate with beaded backfill to bilobate with prominent

levees, reflecting the preservation of progressively deeper levels in the burrow from the

lower left to upper right of the image. (H) Poorly preserved sinuous burrow between twoglacial dropstones.


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Fig. S11.Microbially induced sediment wrinkles interpreted to represent sediment stabilization at

the base of a biomat. Scale bar = 1 cm.


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Fig. S12UPb zircon probability age distributions for detrital zircons from the Permian Tres Islas

Fm (A, B) and the Tacuar trace-fossil bearing strata (C).


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Fig. S13.Colour SEM-CL image of sectioned zircon from granite sample S1086. Note the

prominent regions with banded zoning, consistent with these grains having crystallized

from the granite magma.


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Table S1.U-Pb zircon LA-MC-ICPMS and SHRIMP results for granite samples 080105/3 and

S1086.


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Table S2.

U-Pb ID-TIMS zircon results for granite sample 080105/3 and detrital zircons from theTacuar trace fossil-bearing strata; sample Tacuari-1-2011.


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Table S3.U-Pb Zircon LA-MC-ICPMS results of detrital zircons from Tacuar trace fossil-bearingstrata; sample Tacuari-1-2011.


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Table S4.U-Pb Zircon LA-MC-ICPMS results of detrital zircons from the Tres Islas Formation

(Permian); sample 071220/3.


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