Late Pleistocene To Holocene Climate Variability Recorded In Lake Sediment Of Silver Lake Summit County Ohio

Download or read book Late Pleistocene to Holocene Climate Variability Recorded in Lake Sediment of Silver Lake, Summit County, Ohio written by Corinne M. Lally and published by . This book was released on 2016 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: To provide greater spatial coverage of late Pleistocene to Holocene environmental change in the Midwestern United States, a 1350 cm long sediment core was collected from Silver Lake in northeast Ohio. Age control was provided by new radiocarbon dates, correlation to a dated lake record from western Ohio, and a prior study of Silver Lake. Lithologic descriptions and sedimentary profiles of dry bulk density (DBD), organic matter (OM), carbonate, C/N, grain size, magnetic properties, and concentrations of terrigenous derived elements (Al, Ti, and K) allow the core to be divided into six periods. The climate interpretations are compared to published regional and hemispheric climate records. The first period is Deglaciation, which spans from 17,560 -- 13,600 cal year BP (1353 - 1188 centimeters below lake floor (cmblf)). Silty sediment with low OM (average 6 %) and high DBD (average 0.832 g/cm3) are interpreted to reflect cold conditions soon after deglaciation. The Latest Pleistocene Period is the second period and spans from 13,600 -- 12,200 cal yr BP (1188 -- 1103 cmblf). Brown to light brown mud with silty layers, a slight increase in % OM (average 9 %) and decrease in DBD (average 0.694 g/cm3) characterize this interval. The Latest Pleistocene Period may have been a time of increased primary productivity in Silver Lake. The third period is the Younger Dryas, which spans from 12,200 -- 11,500 cal yr BP (1103 -- 1070 cmblf). Gray-brown to light-brown silty mud having low % OM (average 6%), high DBD (average 0.703 g/cm3), high concentrations of magnetic minerals, and elevated concentrations of Al, Ti, and K characterize this period. These sediment characteristics are interpreted as cold and dry conditions, increased terrigenous input, and/or decreased primary productivity. The fourth period is the Early Holocene which spans from 11,500 -- 7,450 cal yr BP (1070 -- 824 cmblf), and is divided into two subperiods. During the first subperiod, from 11,500 -- 10,600 cal yr BP (1070 -- 1016 cmblf), there was an increase in % OM (average 28 %) and decrease in DBD (average 0.311 g/cm3) and concentrations of Al, Ti, and K. The first subperiod of the Early Holocene is interpreted to be a period of brief warming. The second subperiod of the Early Holocene spans from 10,600 -- 7,450 cal yr BP (1016-824 cmblf), and is characterized by highly variable % OM and DBD and increased Al, Ti, and K. This subperiod is interpreted as a period of increased aridity. The fifth period is the Mid to Late Holocene which spans from 7,450 -- 200 cal yr BP (824 -- 128 cmblf). Alternating brown and dark brown mud having no visible silty layers, high % OM (average 51%), low DBD (average 0.116 g/cm3), and decreased Al, Ti, and K and magnetic concentration characterize this period. These sediment characteristics are interpreted to reflect warm and moist conditions when primary productivity increased and/or terrigenous influx decreased. However, within the Mid to Late Holocene Period there are six pronounced intervals of decreased % OM and increased Al, Ti, and K suggestive of millennial-scale increases in terrigenous input and/or decreases in lake productivity. These six intervals may be related in part to rapid global climate changes during the Holocene, when temperatures and moisture balance fluctuated. The sixth period is the Anthropogenic Period, which spans from 200 cal yr BP to the present (128 -- 0 cmblf). The Anthropogenic Period is characterized by a pronounced decrease in % OM (average 19%), increase in DBD (average 0.273 g/cm3), and an increase in the mass accumulation rate (MAR) resulting from Euro-American land clearance enhancing watershed erosion.