ABSTRACT: Organic Geochemistry and Hydrocarbon Potential of Upper Anthracosia Lake Sediments from the Sudetes Area of Southwestern Poland

YAWANARAJAH, SHAREEN R., Southern Illinois University, Carbondale, IL

Lacustrine synrift sediments are found at three stratigraphic levels in the lower Rotliegendes continental deposits of southwestern Poland. The Autunian Upper Anthracosia lake sediments were sampled at outcrops in Scinawka, in the Intrasudetic basin, and Swierzawa, located 70 km north, in the North Sudetic basin. The sections consist of basal gray mudstones, overlain by organic-rich Upper Anthracosia black shales and succeeded by dark gray mudstones.

The sediments are characterized by features typical of deposition under saline conditions. These include the presence of Beta-carotanes and gammacerane. Relative abundances of both biomarkers and Pr/Ph 1 suggest that lake waters at Scinawka were more saline than at Swierzawa. The identification of sesquiterpanes and head-to-head linked isoprenoids (2,6,9,13-tetramethyltetradecane and 2,6,9,13-tetramethylpentadecane) based on mass spectra and retention times, coupled with high hopane/sterane ratios suggest a predominantly algal and/or microbial source input. Observable kerogen is dominated by lamalginite with little terrestrial material. Botryococcus was noted in the Scinawka shales.

Methylphenanthrene indices (0.42-0.52), triaromatic steroid ratios (0.69-0.83), and Tmax values (450 degrees C) indicate mid-oil window thermal maturity levels at both locations. Average vitrinite reflectances are 0.964 and 0.924 for the Swierzawa and Scinawka sections, respectively. Potential yield and production index values from Rock-Eval pyrolysis show the shales in both sections to have good source rock potential. Increased amounts of generated hydrocarbons and low intensity fluorescence in the observable bitumen of Swierzawa shales suggest migration of generated hydrocarbons into

adjacent lean mudrocks showing anomalously high potential yield and production index values.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)