24. Dynamic Relationship between Subsidence, Sedimentation, and Unconformities in Mid-Cretaceous, Shallow-Marine Strata of the Western Canada Foreland Basin: Links to Cordilleran Tectonics

  1. Cathy Busby8 and
  2. Antonio Azor9
  1. A. Guy Plint1,
  2. Aditya Tyagi1,
  3. Phil J. A. McCausland1,
  4. Jessica R. Krawetz2,
  5. Heng Zhang3,
  6. Xavier Roca4,
  7. Bogdan L. Varban4,
  8. Y. Greg Hu5,
  9. Michael A. Kreitner6 and
  10. Michael J. Hay7

Published Online: 30 JAN 2012

DOI: 10.1002/9781444347166.ch24

Tectonics of Sedimentary Basins: Recent Advances

Tectonics of Sedimentary Basins: Recent Advances

How to Cite

Plint, A. G., Tyagi, A., McCausland, P. J. A., Krawetz, J. R., Zhang, H., Roca, X., Varban, B. L., Hu, Y. G., Kreitner, M. A. and Hay, M. J. (2011) Dynamic Relationship between Subsidence, Sedimentation, and Unconformities in Mid-Cretaceous, Shallow-Marine Strata of the Western Canada Foreland Basin: Links to Cordilleran Tectonics, in Tectonics of Sedimentary Basins: Recent Advances (eds C. Busby and A. Azor), John Wiley & Sons, Ltd, Chichester, UK. doi: 10.1002/9781444347166.ch24

Editor Information

  1. 8

    Department of Earth Science, University of California, Santa Barbara CA 93106, USA

  2. 9

    Departamento de Geodinámica, Universidad de Granada, Campus de Fuentenueva, s/n, 18071 Granada, Spain

Author Information

  1. 1

    Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7, Canada

  2. 2

    Canadian Natural Resources Limited, Suite 2500, 855-2nd Street SW, Calgary, AB, T2P 4J8, Canada

  3. 3

    Apt. 1204, 108, 3rd Avenue SW, Calgary, AB T2P 0E7, Canada

  4. 4

    Imperial Oil Resources, 5th Avenue Place, 237, 4th Avenue SW, Calgary, AB, T2P 3M9, Canada

  5. 5

    Loring Tarcore Laboratories Ltd., #2-666 Goddard Ave. NE, Calgary, AB T2K 5X3, Canada

  6. 6

    Suncor Energy Inc., 150 6th Ave SW, P.O. Box 2844, Calgary, AB T2P 3E3, Canada

  7. 7

    Talisman Energy Inc., Suite 3400, 888, 3rd St. S.W., Calgary, AB T2P 5C5, Canada

Publication History

  1. Published Online: 30 JAN 2012
  2. Published Print: 30 DEC 2011

ISBN Information

Print ISBN: 9781405194655

Online ISBN: 9781444347166

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Keywords:

  • foreland basin;
  • Cretaceous;
  • Canada;
  • flexural subsidence;
  • clastic sequences

Summary

Rocks of the mid-Cretaceous Colorado allogroup and time-equivalent strata (late middle Albian to early Campanian; ∼104 Ma to ∼83 Ma), are dominated by marine mudstone and siltstone that was deposited in a few tens of meters of water up to several hundred kilometers from shore. In the north and west, nearshore and coastal plain facies form relatively minor components of the allogroup. The rocks are divided into allomembers by marine transgressive and flooding surfaces. Allomembers are the fundamental genetic stratal packages, and typically span ∼50-200 kyr. Allomembers are grouped into larger informal “units” (spanning ∼400-800 kyr), and alloformations (spanning a few Myr). Except for the Cenomanian Dunvegan alloformation, rocks of the Colorado allogroup lack well-developed clinoform stratification. The scarcity of clinoforms suggests that supply rate usually exceeded accommodation rate and areas of subsidence were immediately filled with sediment up to a subaqueous “accommodation envelope” defined by effective wave base. Alloformations form prismatic wedges, hundreds of kilometers in dip and strike extent and 100-900m thick. Their component “units” have more arcuate depocenters typically 100-300km in strike length, suggestive of more localized loading. Lateral shifts of depocenters and rotation of isopachs between units suggest that the loci of subsidence, loading, and of inferred active thrust advance, shifted laterally over distances of ∼100-300km in ≪ 1 my. Allomembers, occupying even more localized depocenters of 100-200km strike length, may shift along strike by as much as 300km on the timescale of a single marine flooding surface (i.e., < ∼10 kyr), suggesting that the emplacement of loads was spatially and temporally very non-uniform.

Successive allomembers commonly change upward from wedge- to sheet-shaped rock bodies. Wedges indicate high accommodation and aggradation rates that confined nearshore sandstone and conglomerate to a belt close to the orogenic margin. In contrast, sheets commonly contain highly progradational nearshore sandstone and represent periods of low accommodation rate that favored shallow water and rapid regression.

Two principal depocenters are recognized in the Colorado allogroup. A N-S trending depocenter in northern Alberta and British Columbia accommodated Albian to middle Cenomanian rocks; much of this time is represented by unconformities in the south. In the south, a NW-SE trending depocenter was initiated in the late Cenomanian at ∼95Ma and accommodated late Cenomanian to early Campanian (and younger) rocks; in the northern depocenter, late Cenomanian to late Coniacian time is represented by an unconformity. The switch between the northern and southern depocenters apparently took place very abruptly at ∼95 Ma. We speculate that subsidence of the northern depocenter was related to the collision and clockwise rotation of the Stikine and Yukon- Tanana terranes during their impingement upon the adjoining continental margin. Subsidence of the southern depocenter from 95 Ma onward probably corresponds to the onset of significant dextral transpression during the northward translation of the accreted terranes. Patterns of flexure along the western margin of North America and the evolution of foreland basin depocenters may ultimately have been controlled by the convergence of oceanic plates with North America, but via tectonic mechanisms that acted through the accreted terranes at Cordilleran scale, and through thrust sheet loading, basement weaknesses, and other local factors at the <300 km scale.