Abstract:
Laterally extensive, well-developed clinoforms have been mapped in Early Cretaceous
deposits located in the northeastern 27,000 km2 of the Colvile Basin, North Slope of
Alaska. Using public domain 2-D seismic data, well logs, core photographs, and grain
size data, depositional geometries within the Nanushuk and Torok formations were
interpreted in order to constrain the transport conditions associated with progradation of
the shoreline and construction of the continental margin out of detritus shed from the
ancestral Brooks Range. Using STRATA, a synthetic stratigraphic modeling package,
constructional clinoform geometries similar to those preserved in the North Slope
clinoform volume (32,400 km3) were simulated. Sediment flux, marine and nonmarine
diffusivities, and basin subsidence were systematically varied until a match was found
for the foreset and topset slopes, as well as progradation rates over a 6 milion year
period. The ability of STRATA to match the seismically interpreted geometries allows us
to constrain measures of possible water and sediment discharges consistent with the
observed development of the Early Cretaceous c1inoform suite. Simulations indicate
that, in order to reproduce observed geometries and trends using constant input
parameters, the subsidence rate must be very small, only a fraction of the most likely
rate calculated from the seismic data. Constant sediment transport parameters can
successfully describe the evolution of the prograding margin only in the absence of
tectonic subsidence. However, further work is needed to constrain the absolute
magnitude of these values and determine a unique solution for the NPR-A clinoforms.
