The Role of
Secondary Flow on Facies Associations and Stratigraphic Architecture in Sinuous Slope Channels:
Concepts learned from a 3D exposure of a Sinuous Slope Channel,
Pyles, David1,
Mark Tomasso2, D.C. Jennette3, R.T. Beaubouef4,
C.R. Rossen5 (1) Colorado School of Mines, Golden, CO (2) The
University of Texas at Austin, Austin, TX (3) Apache Oil, Houston, TX (4) ExxonMobil Exploration Co, Houston, TX (5) Exxon Production
Research Co, Houston, TX
The Beacon Channel of the Brushy Canyon
Formation, west
In the Beacon Channel, river-like,
sigmoid-shaped point bars record a time of increasing sinuosity and channel
down cutting. However, unlike in rivers, point bars in the Beacon Channel
contain fine-grained strata partitioned to their lower and upper parts, and
coarse-grained, cross-bedded strata are partitioned to their middle part. These
strata contain greater facies and grain-size
diversity than the rest of the strata in the channel. Paleocurrent
data in the point bars provide evidence that the turbidity currents associated
with them had a secondary component to flow that rotated opposite that of water
in bank-full rivers. In contrast to Beacon Channel point bars, younger strata
related to the filling of the channel are flat-lying, homogeneous, amalgamated
sandstones that progressively onlap the margins of
the channel and contain a fining-upward association. Paleocurrent
data in these strata provide no evidence for a secondary component to flow.
These observations illustrate that flows
and strata associated with increasing the sinuosity and depth of sinuous slope
channels are distinctly different than flows and strata associated with their
fill.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California