A loess–paleosol record of climate and glacial history over the past two glacial–interglacial cycles (~ 150 ka), southern Jackson Hole, Wyoming

Abstract

Loess accumulated on a Bull Lake outwash terrace of Marine Oxygen Isotope Stage 6 (MIS 6) age in southern Jackson Hole, Wyoming. The 9 m section displays eight intervals of loess deposition (Loess 1 to Loess 8, oldest), each followed by soil development. Our age-depth model is constrained by thermoluminescence, meteoric 10Be accumulation in soils, and cosmogenic 10Be surface exposure ages. We use particle size, geochemical, mineral-magnetic, and clay mineralogical data to interpret loess sources and pedogenesis. Deposition of MIS 6 loess was followed by a tripartite soil/thin loess complex (Soils 8, 7, and 6) apparently reflecting the large climatic oscillations of MIS 5. Soil 8 (MIS 5e) shows the strongest development. Loess 5 accumulated during a glacial interval (~ 76–69 ka; MIS 4) followed by soil development under conditions wetter and probably colder than present. Deposition of thick Loess 3 (~ 43–51 ka, MIS 3) was followed by soil development comparable with that observed in Soil 1. Loess 1 (MIS 2) accumulated during the Pinedale glaciation and was followed by development of Soil 1 under a semiarid climate. This record of alternating loess deposition and soil development is compatible with the history of Yellowstone vegetation and the glacial flour record from the Sierra Nevada.

Pedothem carbonates reveal anomalous North American atmospheric circulation 70,000–55,000 years ago

“…Rapid growth of carbonate at this time (Fig. 3G), despite indications of low moisture, may be related to high dust input to WR soils during MIS 2 summers as glacial detritus was mobilized from fluvial systems (40).…”

Spatial and temporal changes in aeolian redistribution of sediments and nutrients following fire

“…Regional studies of soil development and loess deposition (e.g. Pierce et al ., 2011) show increased deposition of loess during glacial intervals, with intervals of surface stability and soil formation during interglacials. While these modern rates only approximate flux during current climactic conditions and measure the gross deposition of material onto the landscape, the 100 ka rates demonstrate the ability of small and steady flux rates to alter landscapes and provide nutrients and sediment to semi‐arid ecosystems (see Table S5 in the online Supporting Information).…”

Atmospheric re-organization during Marine Isotope Stage 3 over the North American continent: sedimentological and mineralogical evidence from the Gulf of Mexico

“…The clay and sedimentological records from the Orca Basin were compared with previously published paleo-environmental records including the Mississippi River discharge intensity (Hill, 2006) and lower Mississippi terrace levels (Rittenour et al, 2005), loess and paleosoil deposition (Forman et al, 1992;Johnson et al, 2007;Wang et al, 2009;Pierce et al, 2011), lacustrine records (Jacobs et al, 2007;Wood et al, 2010), braided vs. meandering river systems in the Atlantic coastal plains (Leigh et al, 2004), pollen association and vegetation (Fredlund, 1995;Baker et al, 2009;Pierce et al, 2011) and summer precipitation over Florida (Grimm et al, 2006;Donders et al, 2011). When we compare data from different cores recovered in the Gulf of Mexico and various continental archives, however, it is important to keep in mind that all records have independent age models which all contain uncertainties.…”