Generalized thermal maturity map of Alaska

This dataset consists of a polygon coverage and associated attribute data derived
from the onshore portion of the 1996 "Generalized Thermal Maturity Map of
Alaska" compiled by M.J. Johnsson and D.G. Howell, which was published as Plate 1
in US Geological Survey Bulletin 2142: "Thermal Evolution of Sedimentary Basins in Alaska".
The published map summarizes vitrinite reflectance and conodont alteration index data
(both measure the thermal maturity of rocks) into generalized units that can be shown
cartographically at 1:2,500,000. This digital dataset includes the 8 map units indicated on the
original map. (5 thermal maturity levels; 2 rock or sediment type; 1 "no data").
The data quality of the generalized information is retained, with an attribute value
for "certainty" whose value choices are "questioned" or "certain". Additional data
retained in a look-up table are the maximum and minimum vitrinite reflectance and
conodont alteration index values assigned to each thermal maturity level.
This coverage is not intended to be a complete representation of the printed
map. It does NOT include the following features: locations of individual
vitrinite or conodont sample data points (these data are available in: Johnsson and
others, 1992, USGS Open File Report 409, 3 diskettes); faults; offshore maturity data
(from dredge and well samples); cities, glaciers, wells; inset maps and subsurface
contours for the Colville basin and Cook Inlet; the correlation chart, text or
references printed on the map.