I'm your #1 Submarine Fan (Wyoming)

You are about to embark on the Journey of the Submarine Fan...

On a trip to find the "ice caves" near Point of Rocks, WY (we didn't find them, and I'm still not sure what they are), we zoomed past what I then called an anticline. Musing for the rest of our drive about continental crust deformation, I set out to find more info...

...and today, I slapped open a Thanksgiving gift (Field Geology Illustrated, Terry S. Maley, 1995) to page 321. Browse back two pages and up at me smiles a familiar outcrop: that exact anticline. What are the chances!

 [insert photo in Field Geo Guide book]

I found out this outcrop is penecontemporaneous slumping within a retrogradational submarine fan of the Cretaceous Blair formation (1)! "No way you found that random Wyoming outcrop in a book..." my friend challenges, but that $5 bet was lost!

Slump axis with beds above reverting to sub horizontal dip. Slumping occurred during or shortly after deposition as a submarine fan on the western margin of the Western Interior Seaway (Fig. 10, reference 7) (GPS 41.669459, -108.940874).


Blair formation found in the yellow box (2). 
Image result for prodelta deposits



It is a prodelta deposit (3), which visually looks like (4): 


Schematic stratigraphic sections illustrating: (A) prodelta deposits seaward of a coastal plain delta like the modern Po; (B) prodelta deposits characterised by a subaqueous o?ap break seaward of the Apennine small rivers (central Adriatic); (C) subaqueous delta fed laterally through shore-parallel circulation and perched on morphological relief on the shelf around the Gargano promontory. Note that storage of sediment in coastal plains is signi?cant in case A, negligible in case B and nil in case C.
Cross sectional view of a prodelta environment, clay rich and poor to non-reservoir deposits (5). Deposited on submarine slopes between the shelf and basin of the Western Interior Seaway, (7).

Campanian (83-72 Ma) paleogeography; note Wyoming's position along the Western Interior Seaway, with a prodelta environment in the yellow circle- the depositional fate for the Blair formation (6). 

Deposited under 250 feet of water (as spoken by trace fossil burrows, flute casts, marine tracks), sediments were sourced from beaches northwest of the Rock Springs uplift. The fans grade upward, _.


References
  1. Field Geology Illustrated, Terry S. Maley, Fig. 7.89, photo by W.R. Hansen, USGS, p. 319
  2. https://pubs.usgs.gov/dds/dds-069/dds-069-d/REPORTS/69_D_CH_14.pdf
  3. https://www.researchgate.net/publication/236516699_Depositional_environments_of_the_Rock_Springs_formation_southwest_flank_of_the_Rock_Springs_uplift_Wyoming
  4. https://www.geol.umd.edu/~jmerck/geol342/lectures/10b.html
  5. https://www.researchgate.net/figure/Schematic-stratigraphic-sections-illustrating-A-prodelta-deposits-seaward-of-a-coastal_fig3_223598623
  6. http://www.searchanddiscovery.com/pdfz/documents/2014/30392blakey/ndx_blakey.pdf.html
  7. Coastal Sedimentation Along a Segment of the Interior Seaway of North America, Upper Cretaceous Baxter Shale, and Blair and Rock Springs Formation, Rock Springs Uplift, Southwest Wyoming, Jan 1994, pg. 7

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