A late Pleistocene–Mid-Holocene noble gas and stable isotope climate and subglacial record in southern Michigan



[1] Stable isotopes (δD, δ18O) and 14C derived ages in the Saginaw aquifer in southern Michigan suggest subglacial meltwater contributions from the Laurentide Ice Sheet of up to 36% in the late Pleistocene, following the Last Glacial Maximum. Contributions of up to 74% from previous glaciation periods are observed. Together with the Marshall record [Ma et al., 2004], noble gas temperatures (NGTs) and excess air (EA) from the Saginaw aquifer capture, for the first time, the onset of the Younger Dryas (∼12.9 kyr BP) with a ∼3.3°C cooling accompanied by drier conditions. Mid-Holocene (MH) climatic shifts are also identified, with warming (∼2.9°C), increased aridity starting at ∼5.4 kyr BP followed by reversal to cooler, humid conditions at ∼4.1 kyr BP. Except for the last MH reversal, the stable isotope record mimics the NGT and EA records. Contrasting trends displayed byδ18O and deuterium-excess in the last MH reversal suggests enhanced vapor transport from the Gulf of Mexico.