A. Contributed Papers

Saskatchewan Geological Survey

2 Summary of Investigations 2000, Volume J

Clues to the Origin, Tectonics, and Hydrocarbon Generation History of the Williston Basin from Apatite Fission Track

Thermochronology

K. G. Osadetz 1, B.P. Kohn 1

, S. Feinstein 3, and P.B. O 'Sullivan 1

Osadctz, K.G. , Kohn, B.P., Feinstein, S. , and O'Sullivan, P.8. (2000): Clues to the origin, tectonics, and hydrocarbon generation history of the Williston Basin from apatite fission track thermochronology; in Summary of Investigations 2000, Volume I, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 2000-4.1 .

/---/

I I

SASKATCHEWAN

,, ,,CEDAR CREEK ANTICLINE

MANITOBA

PETROLEUM PROVINCE

Depth of base Madison (feet)

200 km

Figure I - Regional setting, major tec:tonic elements, and petroleum provinces of the Williston Basin. Basitiform-lines are indicated tliugrammaticully over limited portions of the basin by the depth to the base of the Carboniferous Matlison Group. F, inferred faults in the Precambrian basement.

1. Introduction

In this paper, the Williston Basin proper (Figure 1) is recognized as the sub-circular epicratonic Phanerozoic basin, approximately 800 km in diameter, that is located within the Williston Basin region, a more extensive area of Phanerozoic strata in Manitoba, Saskatchewan, and the adjacent USA (Gerhard et al., 1982). This distinction between the Williston Basin proper and the Williston Basin region reflects a stratigraphic continuity that extends well beyond the epicratonic basin (Burgess el al., 1997) . The Williston Basin region overlies the Paleoproterozoic coll isional Trans-Hudson Orogen, as well as the margins of the Archean Superior and Hearne/Wyoming cratons (Burwash et al., 1994; Leclair et al., 1997). It contains several significant petroleum provinces and mineral deposits which are randomly distributed both geographically and stratigraphically (e.g. Burrus e l al., 1996).

Apatite fission-track (AFT) thermochronology and organic maturity data (Crowley et al., I 985; Crowley and Kuhlman, 1988; Kohn et al., 1995; Osadetz et al. , 1998) indicate spatial and temporal variations in the thermal history of the Williston Basin and adjacent Precambrian Shield of North America (Figures I and 2). On the Canadian Shield and under areas of the Williston Basin region which have thin

' Geo logical Survey o f Canada. 3303 - JJrd Slrcct NW, Calgary. A l3 T2 L 2A 7. ' School o f Earth Sc iences, Uni versity of M elbourne . Victoria 30 I 0. Australia 'De pa rtment of Geological and l'rwironmcntal Sciences. Ben Gurion Univers ity o f the Negev. P.O Box 6 53. M 120 fleer Shcva. Israel.

Saskalche wan Ceo{ogical Survey 3

Group I Example: Rlctvnound (1-31-18-28W3)

0

» 40

T('C).,

., 100

1*1

• •

N • • ..

(A) 2287 metrea depth

-1-~~-,-~~-,.~-.-~.--~~..,-~.--~ - - - - ,., 0

-(Ml)

... UM 1M

t I I 4 I I 7 I I • tt • • Y ~ • ff W ~ •

TNd< IAnglh ("*""-)

Group II Example: Balldon (2·11-15-28W2) 2357 metrN depth

0

:ID

40

T('C).,

• 11111

(BJ

130 ~--,~~~..---.~-,-~...-".__.~-.-~.--~ - - - - ,., 0 n....., -,~ Qli. !I ttt am 1.9

N •

1 I I 4 • • f a • • " U U M W M ff W • a

Tl-* LAlrGlh <-> Figure 2 - Best match thermal history models for Group I (A), u11disturbed exposed Shield or shallowly buried Williston Basin region, and Group II (8), deeply buried Williston Basin proper, samples as defined by Osadetz et al. (/998). Models for Group I samples record regional late Precambrian cooling, whereas Group II models commence with late Paleozoic cooling. Note the similarity of Mesozoic and Cenozoic thermal histories for both groups of samples.

Phanerozoic cover, AFT data typically record late Precambrian cooling followed by intervals of Phanerozoic heating and cooling, the pattern of which mimics the Phanerozoic sedimentation history. Elsewhere, the earlier thermal history is overprinted by resetting of AFT clocks during the Late Paleozoic. The region affected by this Late Paleozoic thermal event includes both a broad portion of the "central basin", extending more than 300 km from the bas in centre where the Phanerozoic succession is up to 5 km thick, and a linear zone, at shallower depths, stretching from

the Williston to Athabasca basins (Figure 2). It thus broadly conforms to the area occupied by the Devonian Elk Point Basin.

2. Interpretation

Our analysis distinguishes the Late Paleozoic event extending into the Williston Basin region from the Early Paleozoic origin of the Williston Bas in proper (Figures 3 and 4). We infer that the Williston Basin proper fonned as the result of at least two distinct thermo-mechanical processes. Initial Ordovician­Silurian subsidence is generally contemporaneous with the initial subsidence of other North American intracratonic basins (Sloss, 1984). It has been attributed by Hamdani et al. (1994), Ahern and Mrkvicka ( 1984), and others to the thennal contraction of a large sill intruded into the lower crust. An upward migration of the Iithosphere-asthenosphere boundary (LAB) in Devonian time provides a plausible mechanism for linking Late Paleozoic and Early Mesozoic tectonic events in the Williston Basin region. These events include accelerated Middle Devonian to Carboniferous subsidence, Late Paleozoic increase in basal heat flow, followed by Late Paleozoic to Early Mesozoic uplift and erosion. They were succeeded by Triassic and Jurassic subsidence signifying the decay of the heat flow anomaly. Whereas accelerated Devonian­Carboniferous subsidence and the Late Paleozoic thermal event took place in essentially the area of the Devonian Elk Point Basin, Early Mesozoic subsidence was restricted to that region where the Elk Point and Williston basins are superimposed. This restriction of Triassic-Jurassic subsidence to the region of the Williston Basin proper is inferred to indicate a mechanical response, probably a phase change, involving the igneous sill responsible for the initial Ordovician-Silurian subsidence of the Williston Basin.

We conclude that the accelerated Devonian­Carboniferous subsidence and the succeeding Late Paleozoic thennal event are both responses to thennal thinning of the continental lithosphere, temporally separated by the thennal inert ia of the continental lithosphere. The differing response between areas within the Williston Basin proper, and those outside, may be due to the effects o f Late Paleozoic heating on the intrusion inferred responsible for initiating Williston Basin subsidence in Early Paleozoic time (Ahem and Mrkvicka, 1984). Therefore the orig in and pattern of Williston Basin subsidence is inferred to be episodic and fortuitous as opposed to continuous and discrete. Other epicratonic basins (e.g. Illinois Basin) exhibit either accelerated subsidence or thermal anomal ies in Late Paleozoic time (e.g. Kominz and Bond, 199 I). Together these may define a previously unrecognized, but widespread and coordinated interaction with the subl ithospheric mantle. A final phase of subsidence contemporaneous with the formation o f the Cretaceous-Paleogene Interior Seaway and Laramide Orogeny ( Figure 3) may be due to other processes interacting with pre-existing lithospheric structure (Burgess e t al., 1997), but without a change in basa l heat flow (Figure 4).

SummmJ' of Investigations 2000, Voh1111e I

0

1000

~ 2000

t • .§. 3000

= Cl. • a 4000

6000

Foreland Basin

6000+---,.~~-~-----...,.....--,.-...... .......,~ ....... ..,....<

600 600 400 300 200 100 Age (Millions of Years)

Figure 3 - Representative Williston Basin burial history model similar to that used to co11strai11 thermal history models. Notice the acceleration of subsidence accomp11nying Kaskaskia/I and Forela11d Basin setlime11tation in the Late Paleowic a11d Early Mesozoic, respectively. Comparison with Figure 2 indicate.~ that the total resetting of AFT clocks during the Late Paleozoic precedes maximum burial in the Paleogene, a clear indication that basal heat flow wa.\" higher in the Late Paleozoic than in the Paleogene.

50

w 0::: ::, i100

w 0. ::!: w 1-150

HIGH ROCK LAKE LAKE ST.MARnN

IMPACT IMPACT

200 800 600 400 200

TIME (Ma)

0

0

Figure 4 - Generalized thermal history models for Group I (undisturbed exposed Shield or shallowly buried Williston Basin region}, G'roup JI (deeply buried Williston Basin proper), and select Group JI/ (High Rock Lake and Lake St. Martin impact crater s,unples generally restricted to the eastern limits of Williston Basin region, as deji11ed by Kohn el al., /995) sample locatio11s. Group JI is distinguished from Group I by the total resetting of AFT clocks in L11te Paleozoic time. Notice that the subselfuent history of Group II and Group Ill samples is similar to that of Group J samples during the Mesozoic and Cenozoic.

Saskatchewan Geological Survey

3. Implications for Petroleum Systems

The Late Paleozoic thermal event identified in this study has great sign ificance for potential petroleum systems in the Sauk and Tippecanoe sequences, both of which reached the oil window for Type II organic matter at that time (Osadetz et al., 1998). Within the region affected by the Late Paleozoic thermal event is a persistent region of elevated heat flows associated with crustal structure, specifically the North American Central Plains Conductivity Anomaly (NACPCA) and the Nesson Anticline (Majorowicz et al., 1988; Figure I). Along the Nesson Anticline, oil windows in Paleozoic strata occur 750 to 1250 m higher in comparison to other regions affected by the Late Paleozoic heating (Osadetz et al., 1989). This persistent geographical heat flow variation is attributed to crustal compositional differences originating during the Precambrian Trans-Hudson Orogeny (Morel-a­l'Huissier et al., 1990). Together these effects suggest early opportunities for hydrocarbon generation, migration and entrapment in the Williston Basin which are not indicated by analysis of the Devonian and Carboniferous petroleum systems alone (Osadetz et al. , 1998).

4. Acknowledgments

This study was supported by the Australian Research Council and the Australian Institute of Nuclear Science and Engineering and Geological Survey of Canada Project 950003. Manitoba Energy and Mines staff and Saskatchewan Energy and Mines staff, especially Dr. D.F. Paterson (retired) and Ms. F.M. Haidl, facilitated the collection of basement samples from petroleum boreholes.

5. References

Ahem, J.L. and Mrkvicka, S.R. ( 1984): A mechanical and thennal model for the evolution of the Williston Basin; Tectonics, v3, no I, p79- l 02.

Burgess, P., Gum is, M., and Moresi, L. ( 1997): Formation of sequences in the cratonic interior of North America by interaction between mantle, eustatic, and stratigraphic process; Geol. Soc. Amer. Bull., v108, p!SIS-1 535.

Burrus, J., Osadetz, K.G. , and Wolf, S. ( 1996): Geochemical and numerical modelling constraints on oil expulsion and accumulation in the Bakken and Lodgepole petroleum systems of the Williston Basin (Canada-USA); Bull. Can. Petrol. Geol. , v43 , p429-445.

Burwash, R.A., McGregor, C.R., and Wilson J. ( 1994): Precambrian basement beneath the Western Canada Sedimentary Basin; in Mossop, G. and Shetsen, I. (comp.), Geo logical Atlas of the Western Canada Sedimentary Basin, Can. Soc. Petrol. Geo I./ Alta. Rescar. Counc., p49-56.

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Crowley, K.D., Ahern, J.L., and Naeser, C. W (1985): Origin and epeirogenic history of the Williston Basin: Evidence from fission-track analysis of apatite; Geol., v 13, p620-623 .

Crowley, K.D. and Kuhlman, S.L. (1988): Apatite thermochronometry of western Canadian Shield: Implications for the origin of Williston Basin, Geophys. Resear. Lett., v 15, no. 3, p22 1-224.

Gerhard, LC., Anderson, S.B., LeFever, J.A., and Carlson, C.G. ( 1982): Geolog ical development, orig in, and energy mineral resources of Williston Basin, North Dakota; Amer. Assoc. Petrol. Geol. Bull., v66, p989-I 020 .

Hamdani, Y., Mareschal, J.-C., and Arkani-Hamed, J. ( 1994): Phase change and thermal subsidence of the Williston Basin; Geophys. J. Intern. , vi 16, p585-597.

Kohn, B.P., Osadetz, K.G., and Bezys, R.K. (1995): Apatite fission-track dating of two crater structures in the Canadian Williston Basin; Bull. Can. Petrol. Geo!., v43, no I , p54-64.

Kominz, M.A. and Bond, G.C. (1991): Unusually large subsidence and sea-level events during Middle Paleozoic time: New evidence supporting mantle convection models for super continent assembly; Geol., vl9, p56-60.

Leclair, A.O., Lucas, S. B., Broome, H.J., Yiljoen, D.W., and Weber, W. (1997): Regional mapping of Precambrian basement beneath Phanerozoic cover in southeastern Trans-Hudson Orogen, Manitoba and Saskatchewan; Can. J. Earth Sci., v34, p6 I 8-634.

Majorowicz, J.A., Jones, F.W., and Osadetz, K.G. ( 1988): Heat flow environment of the electrical conductivity anomalies in the Williston Bas in, and occurrence of hydrocarbons; Can. Bull. Petrol. Geol., v36, no 1, p86-90.

Morel-a-I'Huissier, P., Green, A.G ., Jones, A.G ., Latham, T., Majorowicz, J.A. , Drury, M.J. , and Thomas, M.D. (1990): The crust beneath the Williston Basin from geophysical data; in Pinet, B. and Bois, C. (eds.), The Potential of Deep Seismic Reflection for Hydrocarbon Exploration, Edition Techniq., pl4 l-160.

Osadetz, K.G. , Kohn, B.P. , O'Sullivan, P. , Feinstein, S., Hannigan, P.K., Everitt, R.A., Gilboy, C.F., Bezys, R.K. , and Stasiuk, L. D. ( 1998):

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Thermotectonics of the Williston Basin and environs: Variations in heat flow and hydrocarbon generation; in Christopher, J.E., Gilboy, C.F., Paterson, D.F., and Bend, S.L. (eds.), Proceedings of the Eighth International Williston Basin Symposium, Sask. Geo!. Soc ., Spec. Pub!. No. 13, pl47-165.

Osadetz, K.G. , Snowdon, L.R., and Stasiuk, L.D. ( 1989) : Association of enhanced hydrocarbon generation and crustal structure in the Canadian Williston Basin; in Current Research, Part D, Geo!. Surv. Can., Paper 89-1 D, p35-47.

Sloss, L.L. (1984) : Comparative anatomy ofcratonic unconfonnit ies; in Sch lee, J.S. (ed.), Interregional Unconfonn ities and Hydrocarbon Accumulation, Amer. Assoc. Petrol. Geo!., Mem. 36, p 1-6.

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