--> --> The Sauk-Tippecanoe Megasequence Boundary in Ohio and Northern Virginia: testing the correlation using Sr isotope stratigraphy

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The Sauk-Tippecanoe Megasequence Boundary in Ohio and Northern Virginia: testing the correlation using Sr isotope stratigraphy

Abstract

The early Paleozoic carbonate succession of the Laurentian epeiric sea (Great American Carbonate Bank, herein GACB) holds major oil resources, but precise regional correlation of these strata remains a difficult task due to temporal uncertainty in biostratigraphic range zones and/or scarcity of index fossils. The marine Sr isotopic record (87Sr/86Sr)—preserved in calcium carbonate and biogenic apatite—is a globally averaged signal due to the long oceanic residence time of Sr (~2.5 Myr), and is therefore a potentially useful tool for correlating carbonate strata of the Laurentian epeiric sea. I propose to correlate the Sauk-Tippecanoe sequence boundary—a major target for oil production in the GACB—in the subsurface of Ohio to equivalent strata that outcrop in Northern Virginia (Tumbling Run road cut) using high-resolution (meter-scale sampling) 87Sr/86Sr chemostratigraphy. I will analyze pristine micrite in polished sections of core (Ohio) and outcrop (Virginia) samples, and use the existing Ordovician Laurentian 87Sr/86Sr curve that is calibrated to conodont biostratigraphy to fit my data into the temporal framework of the Geologic Timescale. I expect to see a significant jump in 87Sr/86Sr values from ~0.7084 to ~0.7082 in Virginia, and from ~0.7088 to 0.7082 in Ohio. This work represents an important test of the sequence stratigraphic framework of Ordovician strata of the GACB.