Dave Bowen presentation at EarthScope 2019 workshop

1. The View from (of) the Top:
Considerations of the Phanerozoic
Stratigraphic Cover on the
Wyoming Craton
David W. Bowen
Department of Earth Sciences
Montana State University

2. Purpose – Comprehensive review of
Phanerozoic Stratigraphy above the
Wyoming Craton in 10 minutes!
• Not so much
• Brief review of Tectonostratigraphic Evolution
• Strata
• Unconformities
• What I find interesting and would like to better
understand

3. Phanerozoic Stratigraphic Cover
of the Wyoming Craton
WYOMING
USGS, 1974
(From May et al., 2013)
(from Mueller and Frost, 2006)
Bighorn Basin

4. Tectonostratigraphic Evolution
Cambrian Flathead Sandstone overlying Precambrian in Wind River
Canyon. Madison Limestone and Bighorn Dolomite on Skyline. Photo
courtesy of Alan VerPloeg (WSGS)
385 Ma
*
Antler arc approaches
and collides
with Cordilleran
miogeocline
(From May et al., 2013)
Cambrian
(542 - 488 Ma)
Ordovician
(488 - 444 Ma)
Devonian (416- 359 Ma)

5. Tectonostratigraphic Evolution
325 Ma
*
300 Ma
*
Pennsylvanian (318- 299 Ma)
Mississippian
(359- 318 Ma)
(From May et al., 2013)
275 Ma
*
Phosphoria Retort Shale
Permian (299 -251Ma)

6. Tectonostratigraphic
Evolution
(From May et al., 2013)
Jurassic (200 -146 Ma)
Cretaceous (146- 65 Ma)
75 Ma
*

7. Tectonostratigraphic Evolution
(From May et al., 2013)
Cambrian
(542 - 488 Ma)
Ordovician
(488 - 444 Ma)
Devonian (416- 359 Ma)
40 Ma
*
Quaternary
*

8. P.K. Sims, J.M. O’Neill, Viki Bankey, and E. Anderson, 2004
Nye-Bowler
Basement Structural Weaknesses are Reactivated throughout
Geologic Time and Influence Depositional Patterns Spatially and
Development of Unconformities

9. Strata Bound by Regional
Unconformities
(From May et al., 2013)

10. ~ 30 my
~ 30 my
~ 30 my
~ 10 my
~ 30 my
(From May et al., 2013)
(from Sloss, 1963)
(from Johnson and Clyde, 2016)

11. The seas came in and the seas went out!
• The seas came in and the seas went out
• Plates collided
• Basins Subsided
• “Sloss” unconformities (2nd order), “Milankovitch” unconformities (4th
order, 5th order), but doesn’t explain many unconformities (mostly 3rd
order) and stratal thickness distributions.
• Role of dynamic topography interacting with basement weaknesses?

12. Modeled temporal evolution of Farallon slab (shown in
blue) subducting under North America leading to
differential dynamic topography patterns, with down-
warping of overlying continental lithosphere.
(from Cloetingh and Haq, 2015)
Next? – May be “in-
sync” or “out of sync”
with sea level changes
or tectonic events?