BRYANT, TERRY WAYNE, and ROBERT A. GASTALDO, Auburn University, Auburn, AL
ABSTRACT: Criteria to Aid in the Establishment of Genetic Boundaries Within a Carboniferous Basin: Mary Lee Coal Zone, Black Warrior Basin, Alabama
The upper part of the Mary Lee coal zone of the Lower Pennsylvanian (Westphalian A) Pottsville Formation in northwestern Alabama is composed of the Mary Lee and the Newcastle coal seams. The Mary Lee coal seam has been economically significant in terms of both mining and coal-bed methane production. A sedimentological, paleontological, and geochemical investigation of the lithologies associated with this coal zone was done to define the changes that occur in facies changing from terrestrial into marine facies. A ravinement bed, ranging in thickness from 13.0 to 60.0 cm, marks the boundary between marine and terrestrial deposits. Fifteen surficially exposed sections were observed and sampled in the study area.
Geochemical analyses were done on samples collected from seven sections along the perimeter of the study area. The analyses conducted involved inductively coupled atomic plasma spectrometry (ICAP) for seven elemental oxides that include aluminum, iron, silica, calcium, potassium, magnesium, and manganese. Atomic absorption was used to determine sodium content. Carbonate carbon was determined by weight percent difference after hydrochloric acid treatment, whereas organic carbon content was determined by use of a carbon analyzer on a LECO(tm) induction furnace. Sulfur content was also determined by a LECO induction furnace equipped with a sulfur analyzer. Loss-on-ignition (LOI) percentage was based upon change in weight of samples after a period of 30 min in a muffle furnace at a temper ture of 1000 degrees C.
The combination of sedimentological, paleontological, and geochemical characteristics were used to better understand the depositional setting of the upper Mary Lee coal zone in terms of a transgressive event. These criteria can be used in similar basin systems to better understand the depositional history of those settings.
AAPG Search and Discovery Article #90989©1993 GCAGS and Gulf Coast SEPM 43rd Annual Meeting, Shreveport, Louisiana, October 20-22, 1993.