Reworked Palynomorph Trends in Late Jurassic to Neocomian Strata of the Colville Delta Region, Alaska

By

H. Haga and M.B. Mickey (Micropaleo Consultants, Inc.)

Palynologists have long recognized the presence of reworked palynomorphs in strata of the North Slope region of Alaska. The reworked forms are a reflection of the formational units from which they were derived, and provide indirect evidence of the detrital contributors to a given depositional site. Coarser clastic source units have petrographic and mineralogic characteristics that are utilized in provenance determinations; and data about the reworked palynomorph content can add to the confidence of such interpretations.

A study of 25 wells from the Colville Delta area in northern Alaska was undertaken to identify and quantify the reworked palynomorph fractions in the Oxfordian, Valanginian and Hauterivian stratigraphic intervals. These units were examined in detail, with the specific objective of tabulating the ages, frequencies and abundance of the various reworked taxa.

The tracking of reworked palynomorphs indicates that Carboniferous units were a major source of detritus during Oxfordian deposition. Devonian and Permian to Triassic age formations were secondary contributors. A similar pattern persisted through Valanginian and Hauterivian deposition, with the addition of Jurassic age detritus to the reworked mix. The Valanginian and Hauterivian intervals show a progressive decrease in reworked palynomorphs, culminating in almost a total lack of reworking during post-Hauterivian (Barremian —Aptian) deposition.

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.