EPEIRIC C13carb RECORD FROM THE MIDDLE AND UPPER DEVONIAN CEDAR VALLEY GROUP-IOWA BASIN OF CENTRAL NORTH AMERICA

Estimates of subtropical Iowa Basin sea surface temperatures (SSTs) interpreted from δO¹⁸ values of conodont apatite from the Cedar Valley Group document progressive warming and SST maxima during the Middle and Late Givetian, respectively, followed by Late Givetian cooling during the Upper disparilis and norrisi zones, and resumed warming during the Early to Middle Frasnian. New δC¹³_carb data from the same localities sampled for conodonts to estimate the SST profile document 17 carbon isotopic excursions through the same interval. Paired +2‰ δC¹³_carb excursions 1A and 1B coincided with deposition of the Middle Givetian Solon Member of the Little Cedar Formation and marine flooding of the Taghanic Onlap (Cratonic North American Devonian Transgressive-Regressive (T-R) cycle IIa-1A = Iowa Devonian T-R cycle 3A). Low magnitude (0.5‰) δC¹³_carb excursions 2 to 6 are associated with resumed sea level rise and highstand of Cratonic Devonian T-R cycle IIa-1B (Iowa T-R cycle 3B) where δO¹⁸ values indicate warming and a Late Givetian (hermanni Zone) SST maxima in the Iowa Basin. Excursions 7 and 8 (1 to 1.5 ‰) are associated with Cratonic Devonian T-R cycle IIa-2 (Iowa T-R cycle 4), pronounced SST cooling, a terminal sea level lowstand, and associated Upper disparilis Zone extinction. Excursions 9 to 14 are recorded within the latest Givetian to Early Frasnian Lithograph Formation and are coincident with 3 sea level flooding events and resumed SST warming of during the interval of Cratonic Devonian T-R cycles IIb-1 to IIb-3. Middle Frasnian Shell Rock Formation platform carbonates record excursions 15 to 17 and were deposited during three sea level fluctuations (Iowa Devonian T-R cycles 5A to 5C) during the interval of Euramerican Devonian T-R cycle IIc. Observed δC¹³_carb values of +2.5‰ to - 1.0‰ characterize excursion 15, followed by low magnitude excursions 16 and 17 recording fluctuations in the range of +0.5-1.0‰. Iowa Devonian excursions 1A and 1B are the first notable positive δC¹³ excursions associated with the Tagnahic Onlap, although a major global organic-carbon burial event at that time is not widely preserved in Devonian basins. Excursion 15 coincides directly the global punctata Zone Event that is recorded in western Canada and Eurasia.