This study maps the facies architecture and geometry of stratigraphic surfaces within
the tide-influenced upper Sego Sandstone exposed in the Book Cliffs between Crescent
Junction and Thompson Springs, Utah. A bedding diagram was constructed by
correlating 32 measured stratigraphic logs across this 8.5 kilometer strike-oblique outcrop
to interpret depositional environments and the sequence stratigraphic setting of this
tidally-influenced sandstone. Five facies associations are defined: marine shale, lower
shoreface, tidally-influenced bedsets, heterolithic tidal bedsets, and tidal flat deposits.
Vertical facies trends define two sandy intervals separated by a marine shale, that are
interpreted to record episodic progradation of deltaic shorelines. Erosion surfaces at the
base of these intervals are interrupted to record tidal scouring of the sea floor during
falling stage regression. Sandstone-bodies within these intervals shingle westward
recording delta lobes that thinned and became more heterolithic. Although sandstone
intervals are interpreted to record progradation, internal cross stratification is dominantly
tidal-flood oriented. This is interpreted to record preferential preservation of bedload
transported by flood tidal currents onshore, even though net sediment was directed offshore in a suspended ebb-oriented hypopycnal plume and as fluid mud during
uncommon river floods. Deposits above high-relief erosion surfaces observed to cut
down into the upper Sego Sandstone do not meet the criteria for incised valley fills.
These surfaces are interpreted to record tidal current enlargement of distributary channels
after abandonment. Such incisions thus do not necessarily record changes in sea level.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/3326 |
| Date | 12 April 2006 |
| Creators | Birkhead, Stanley Scott |
| Contributors | Willis, Brian |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 30201211 bytes, electronic, application/pdf, born digital |
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