Alaska Science Center

U.S. Geological Survey
Professional Paper 1732-D

Estimating the Amount of Eroded Section in a Partially Exhumed Basin from Geophysical Well Logs: An Example from the North Slope

By W. Matthew Burns, Daniel O. Hayba, Elisabeth L. Rowan, and David W. Houseknecht


Figure 10 is a full-color sketch map of the Chukchi and Beaufort Seas offshore from the Alaskan North Slope, showing color-coded contours of the estimated amount of exhumation derived from downhole vitrinite-reflectance profiles of wells in the study area.
Alaskan North Slope, showing contours (in feet) of estimated amount of exhumation derived from downhole vitrinite-reflectance profiles of wells in study area and nearby offshore areas. ANWR, Arctic National Wildlife Refuge; NPRA, National Petroleum Reserve in Alaska (from figure 10).


The reconstruction of burial and thermal histories of partially exhumed basins requires an estimation of the amount of erosion that has occurred since the time of maximum burial. We have developed a method for estimating eroded thickness by using porosity-depth trends derived from borehole sonic logs of wells in the Colville Basin of northern Alaska. Porosity-depth functions defined from sonic-porosity logs in wells drilled in minimally eroded parts of the basin provide a baseline for comparison with the porosity-depth trends observed in other wells across the basin. Calculated porosities, based on porosity-depth functions, were fitted to the observed data in each well by varying the amount of section assumed to have been eroded from the top of the sedimentary column. The result is an estimate of denudation at the wellsite since the time of maximum sediment accumulation. Alternative methods of estimating exhumation include fission-track analysis and projection of trendlines through vitrinite-reflectance profiles. In the Colville Basin, the methodology described here provides results generally similar to those from fission-track analysis and vitrinite-reflectance profiles, but with greatly improved spatial resolution relative to the published fission-track data and with improved reliability relative to the vitrinite-reflectance data. In addition, the exhumation estimates derived from sonic-porosity logs are independent of the thermal evolution of the basin, allowing these estimates to be used as independent variables in thermal-history modeling.

Download this paper as an 18-page PDF file (pp1732d.pdf; 4.1 MB)

For questions about the content of this report, contact David Houseknecht

Back to Studies by the U.S. Geological Survey in Alaska, 2005

Download a current version of Adobe Reader for free

| Help | PDF help | Western reports main page | Western Professional Papers |
| Geologic Division | Alaska Science Center | Western Energy Resources |

This report is available only on the Web

Accessibility FOIA Privacy Policies and Notices

Take Pride in America home page. logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: Michael Diggles
Page Last Modified: October 9, 2007