Mountain Building, Regional Diagenesis, and Magnetite Authigenesis in Alleghenian Foredeep

Chad McCabe

In recent years a number of diagenetic features have been linked to regional events, possibly resulting from large-scale migration of fluids driven by orogenesis. These features include, but are not limited to, authigenic feldspar development, clay mineral transformations, and the formation of diagenetic hematite and magnetite. This presentation will focus on magnetite authigenesis and its implications for the nature, origin, and timing of regional diagenetic events in the foreland basin setting.

Recent studies in New York State indicate that authigenic magnetite content in Devonian carbonates correlates very well with paleotemperature estimates in an east-west profile. Magnetite grain size also shows a systematic variation across the transect. We can infer from this data set that magnetite authigenesis occurred during maximum burial of the basin during Alleghenian time, but that temperature was not the only controlling influence. Paleomagnetic data from the same carbonate units indicates that the magnetization was also acquired during the Alleghenian rather than during subsequent basin unroofing.

These observations can be seen as evidence in favor of a large-scale diagenetic event of Alleghenian age that resulted from landward migration of basinal fluids. The nature of the fluids remains unknown, although previous speculation that they may have included hydrocarbons now appears unlikely, at least in the New York setting. Paleotemperatures there were simply too high.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.