Comparing
Mesozoic and Cenozoic Mixed Carbonate-Siliciclastic
Systems From A
Coffey, Brian P.1, Richard
Sunde2, J. Fred Read3 (1) Simon Fraser University, Chapel
Hill, NC (2) Simon Fraser University, Burnaby, BC (3) Virginia Tech,
Blacksburg, VA
Regional lithology-based
sequence stratigraphic frameworks constructed across
the subsurface of the
Previous interpretation of the Paleogene depositional facies
successions concluded that deposition was heavily influenced by paleolatitudinal position (subtropical to warm-temperate),
coupled with the major global transition from greenhouse to icehouse
conditions. However, examination of more deeply buried Lower Cretaceous mixed
carbonate-siliciclastic strata from the same basin
reveals carbonate lithofacies that closely resemble
late Paleogene updip shelf facies and stacking patterns consisting of admixed quartz
sands/silts and mollusk-foraminifera dominated skeletal carbonate sands. Deep
shelf marls also are comparable. Preliminary analyses suggest that facies similarities also exist into the underlying Upper
Jurassic interval.
These observations suggest that while eustasy and climate strongly influence thickness and
stacking patterns, the paleogeographic position of
the shelf as a promontory exposed to open ocean wave energy and currents plays
a major role in facies development through time. This
shelf position subjected the waters of the basin to repeated pulses of
ocean-derived elevated nutrient levels, similar to the modern palimpsest
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California