Depositional Models and Sequence Stratigraphic Framework for the “Upper Devonian” Geneseo Formation in the Northern Appalachian Basin, NY: Implications for Hydrocarbon Play Element Quality and Distribution

Abstract

The Middle Devonian Geneseo Formation and its lateral equivalents in the Northern Appalachian Basin are regarded as crucial secondary targets to the extensively explored Marcellus Sub-group. High-resolution sedimentology, sequence stratigraphy, and geochemistry has yielded differentiation of genetically related packages, comprised of distinct lithofacies with characteristic physical, biological, and chemical attributes. Correlations within this mudstone-rich succession are conducted at the parasequence scale, and are based on detailed descriptions of multiple drill cores, surface exposures, and subsurface mapping.

Furthermore, carbon-isotope geochemistry of organic-matter is utilized for regional correlation at the parasequence-scale, and demonstrate the importance of depositional environment and shoreline proximity for organic-matter type and richness. Isopach maps identify thickness trends and lateral variations of mudstone properties (i.e., composition, ductility, etc.). The Geneseo Formation herein has been subdivided into two depositional sequences and comprises three lithostratigraphic units (i.e., Lower Geneseo, Fir Tree, and Upper Geneseo members respectively). The Lower and Upper Geneseo members show systematic aggradational to progradational parasequence stacking patterns, as well as downlap-onlap stratal terminations with underlying strata representing a highstand systems tract (HST). The Fir Tree Member truncates the underlying Lower Geneseo, shows progradational-aggradational-retrogradational parasequence stacking patterns (composite LST and TST), and separates the Lower from Upper Geneseo members respectively.

Thickness variation throughout the Geneseo Formation suggests reactivation of basement structures and syndepositional faulting appears to have strongly influenced accommodation during deposition of the Geneseo Formation. In particular, the N-S trending Clarendon-Linden Fault System which appears to have acted as a western sediment barrier during Geneseo Time. Through the development of a fully integrated sequence stratigraphic framework and incorporation of surface and subsurface data, hydrocarbon play element quality and distribution can be evaluated away from sample control which is critical for economic success. Variations in mudstone properties within the Geneseo succession can be directly linked to presence, quality, and distribution of hydrocarbon source and reservoir.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018