Sedimentation
as the Result of Interplay of Tectonics and Sea Level Change: Evidence from
Pennsylvanian to Early Permian Tensleep Sandstone in Wyoming
Zhang, Qingsheng1, Dag Nummedal2 (1) Parallel Data Systems, Stafford, TX (2) Colorado School of Mines, Golden, CO
Two geological conditions controlled the
sedimentation of the Pennsylvanian to Early Permian Tensleep
Sandstone: the uplift of Ancestral Rocky Mountains due to the collision between
the North American Plate and Gondwana Continent, and
the high-frequency and high-amplitude sea level change due to the glaciation in the southern hemisphere. Outcrop studies at
the Middle Fork of the Powder River and Fremont Canyons,
and core and well log study at the Teapot Dome, indicate the Tensleep Sandstone represents an overall forestepping mega-sequence caused by the uplift of
Ancestral Rocky Mountains. The mega-sequence, which was influenced by numerous
marine transgressions caused by the high-frequency and high-amplitude sea level
change, contains multiple sequences. A typical sequence in the Tensleep Sandstone contains a lowstand
eolian sand dune, interdune
or sand sheet facies, a transgressive
coastal sabkha, interdune
or shoreface facies, a high
stand epeiric marine carbonate facies
and a sequence boundary at the top. The sequence boundaries can be recognized
with erosional surfaces, paleosol,
facies change, conglomerates, karst,
carbonate breccia and gamma ray intensity change.
Correlation indicates that six basal sequences onlap
from the Middle Fork of the Powder River to the Fremont Canyon, reflecting the
presence of the Pathfinder Uplift to the south during Tensleep
deposition period. This study provides an example to show that the development
of sequences and sequence boundaries in the Tensleep
Sandstone which was deposited in a stable and flat shelf environment is the
result of the interplay of tectonics and sea level change.