A "Hot" New Shale Facies from the Carboniferous of Northern England

MAYNARD, JAMES ROBERT, and PAUL BARRY WIGNALL, Leeds University, Leeds, U.K.

Thin black shales (marine bands) are well known from Carboniferous of northwest Europe where they occur as maximum flooding surfaces, each with a distinct fauna. Their C/S marine signature and authigenic uranium enrichment, combined with their widespread occurrence over many thousands of kilometers, have made them of fundamental use in downhole correlation.

However, a new black shale facies has been discovered that also has high TOC and authigenic uranium values, a marine geochemical signature but, in this case, no associated fauna. This has serious implications for downhole correlation where only the marine bands have been considered to have this signature. Correlation of the new shale type has shown that they form the basal marine flooding surface of transgressive systems tract in the Pennine basin of northern England. Thus they are of less areal extent than the marine bands. Downhole correlation therefore requires that these two black shale types are distinguished. However, the presence of a transgressive black shale type substantially increases the source rock potential of the basin.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)