Organic-carbon–rich shales of the lower Marcellus Formation were deposited at the toe and basinward of a prograding clinothem associated with a Mahantango Formation delta complex centered near Harrisburg, Pennsylvania. Distribution of these organic-carbon–rich shales was influenced by shifts in the delta complex driven by changes in rates of accommodation creation and by a topographically high carbonate bank that formed along the Findlay-Algonquin arch during deposition of the Onondaga Formation. Specifically, we interpret the Union Springs member (Shamokin Member of the Marcellus Formation) and the Onondaga Formation as comprising a single third-order depositional sequence. The Onondaga Formation was deposited in the lowstand to transgressive systems tract, and the Union Springs member was deposited in the transgressive, highstand, and falling-stage systems tract. The regional extent of parasequences, systems tracts, and the interpreted depositional sequence suggest that base-level fluctuations were primarily caused by allogenic forcing—eustasy, climate, or regional thermal uplift or subsidence—instead of basement fault reactivation as argued by previous workers. Paleowater depths in the region of Marcellus Formation black mudrock accumulation were at least 330 ft (100 m) as estimated by differences in strata thickness between the northwestern carbonate bank and basinal facies to the southeast. Geochemical analysis indicates anoxic to euxinic bottom-water conditions. These conditions were supported by a deep, stratified basin with a lack of circulation.
Added on 28 February, 2014
The origin of thermogenic natural gas in the shallow stratigraphy of northeastern Pennsylvania is associated, in part, with interbedded coal identified in numerous outcrops of the Upper Devonian Catskill and Lock Haven Formations. Historically documented and newly identified locations of Upper Devonian coal stringers are shown to be widespread, both laterally across the region and vertically throughout the stratigraphic section of the Catskill and Lock Haven Formations. Coal samples exhibited considerable gas source potential with total organic carbon as high as 44.40% by weight, with a mean of 13.66% for 23 sample locations analyzed. Upper Devonian coal is thermogenically mature; calculated vitrinite reflectances range from 1.25% to 2.89%, with most samples falling within the dry-gas window. Source potential is further supported by gas shows observed while drilling through shallow, identifiable coal horizons, which are at times located within fresh groundwater aquifers. Thermogenic gas detected in area water wells during predrill baseline sampling is determined not only to be naturally occurring, but also common in the region.
Added on 31 January, 2014
Some surprising findings bubbled up in a recent study of methane geochemistry in the Appalachian Basin. The findings could complicate the jobs of investigators trying to determine how stray methane gets into water wells.
Added on 01 June, 2014
Explorer Division Column DPA
During my term as DPA president this year our theme will be “Culture of Greatness.” This may sound arrogant, but I think it is important to recognize and promote the culture of professionalism and discovery that has provided cheap energy for mankind for more than 100 years.
Added on 01 July, 2014
Innumerable geoscientists worldwide are familiar with the AAPG Giant Oil Fields publications. These AAPG members are spearheading the effort to compile “Giant Oil and Gas Fields of the Decade 2000-2010” featuring papers covering fields in areas around the globe.
Added on 01 January, 2015
A geoscience company some have billed as “Silicon Valley meets the oil patch” has undertaken a study over the Allegheny National Forest in Pennsylvania. Airborne geophysical datasets newly acquired by NEOS GeoSolutions were combined with existing seismic, well, and public domain datasets to better understand the potential of the Marcellus resource play in a roughly 2,500 square-mile area of investigation.
Added on 01 October, 2014
This year, URTeC has added an enhanced preview of “Coming Attractions.” In addition to looking at established plays, URTeC will provide significant information about emerging unconventional resource possibilities in North America and around the world.
Added on 01 July, 2014
Explorer Foundation Update
It has a new name, a new energy and a new lineup of experts, all primed to spread geoscience knowledge around the world. “It” is AAPG’s newly named Global Distinguished Lecture Program – emphasis on the “global” – which dates back to 1941 but continues to be the Association’s flagship initiative for offering the latest in geologic science to AAPG affiliated geological societies and universities.
Added on 01 October, 2014
Explorer Policy Watch
Over the course of four months the House Natural Resources Committee, chaired by Doc Hastings (R-Wash.), or its Energy and Mineral Resources Subcommittee, chaired by Doug Lamborn (R-Colo.), hosted seven hearings celebrating energy education and employment.
Added on 01 August, 2014
This forum is an intensive one-day review by experts of the latest findings regarding the productive extent and producibility in the Granite Wash of Oklahoma and Texas, along with Pennsylvanian sand-producing horizons.
Added on 23 July, 2014