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Isopach map of interval between top of the Pictured Cliffs Sandstone and the Huerfanito Bentonite bed of the Lewis Shale, La Plata County, Colorado, and Rio Arriba and San Juan counties, New Mexico

Miscellaneous Field Studies Map 1831

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Abstract

This thickness map of a Late Cretaceous interval in the northwestern part of the San Juan Basin is part of a study of the relationship between ancient shore 1ines and coal-forming swamps during the filial regression of the Cretaceous epicontinental sea. The top of the thickness interval is the top of the Pictured Cliffs Sands tone. The base of the interval is a thin time marker, the Huerfanito Bentonite Bed of the Lewis Shale. The interval includes all of the Pictured Cliffs Sandstone and the upper part of the Lewis Shale. The northwest boundary of the map area is the outcrop of the Pictured Cliffs Sandstone and the Lewis Shale.

Data used for the isopach map are mostly from interpretation of geophysical logs of oil and gas wells, southeast of the outcrop in parts of the Cortez, Durango, Farmington, and Navajo Reservoir 1: 100,000-scale quadrangles, Colorado and New Mexico. Cross sections A-A’ and B-B' give examples of geophysical logs that show some of the variations in the isopach interval.

Study Area

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Isopach map of interval between top of the Pictured Cliffs Sandstone and the Huerfanito Bentonite bed of the Lewis Shale, La Plata County, Colorado, and Rio Arriba and San Juan counties, New Mexico
Series title:
Miscellaneous Field Studies Map
Series number:
1831
Year Published:
1986
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Description:
2 Plates: 37.83 x 52.35 inches and 40.54 x 39.40 inches
Country:
United States
State:
Colorado, New Mexico
Scale:
0
Online Only (Y/N):
N
Additional Online Files (Y/N):
N