Paleo Source-Rock Characteristics of the Kuna Formation in the Western Brooks Range

By

A.C. Banet (Bureau of Land Management) and K.R. Evans (StratiGraphix)

Exposures of the Kuna Formation (Mississippian) in theWulik River area of the westernmost Brooks Range are composed of interbedded black shale, mudstone and chert. These basinal facies are equivalent (or partially equivalent) to the Kayak Shale and the Utukok Formation of the Lisburne Group, which are exposed on nearby multiply repeated thrust sheets. The unfaulted Kuna is up to six hundred feet thick. Hand-held scintillometer surveys provide a quick, inexpensive first look at potential source rocks and a tool to assist in correlating with well logs. Measurements of three sections show that the shale facies of the Kuna yields scintillometer profiles comparable to other North Slope source facies. The Kuna contains up to 14% total organic carbon (TOC), however thermal maturities are well beyond the petroleum generation, as is expected considering the tectonic regime in this area. Base metal exploration in the western Brooks Range shows that the Kuna is multiply repeated in thrust sheets and may have potential for natural gas. Although the areal extent of the Kuna is not well constrained, its organic-rich facies may have played an integral part of Brookian orogenic activities. An early phase of hydrocarbon generation from the Kuna may be related to enigmatic bitumen found in Lisburne limestones in the Brooks Range. Its gas resource potential may be tested soon. 

AAPG Search and Discovery Article #90008©2002 AAPG Pacific Section/SPE Western Region Joint Conference of Geoscientists and Petroleum Engineers, Anchorage, Alaska, May 18–23, 2002.