Endogenic carbonate sedimentation in Bear Lake, Utah and Idaho, over the last two glacial-interglacial cycles

摘要: Sediments deposited over the past 220,000 years in Bear Lake, Utah and Idaho, are predominantly calcareous silty clay, with calcite as dominant carbonate mineral. The abundance of siliciclastic sediment indicates that River usually was connected to Lake. However, three marl intervals containing more than 50% CaCO 3 were during Holocene last two interglacial intervals, equivalent marine oxygen isotope stages (MIS) 5 7, indicating times when not lake. Aragonite is mineral these high-carbonate intervals. high-carbonate, aragonitic coincide warm continental climates Pacifi c sea-surface temperatures. also a carbonate-cemented microbialite mound formed southwestern part lake several thousand years. history sedimentation Lake documented through study isotopic ratios oxygen, carbon, strontium, organic carbon content, X-ray diffraction mineralogy, HCl-leach chemistry on samples from traps, gravity cores, piston drill microbialites. Sediment-trap studies show precipitates surface waters today high-Mg calcite. began precipitate highMg sometime mid‐twentieth century after artifi cial diversion into 1911. This drastically reduced salinity Mg 2+ :Ca water changed primary aragonite sediment-trap core accumulating fl oor today, even though it precipitating waters. this derived reworking redistribution shallow-water at least 50 yr old, probably older. Apparently, stopped forming cement diversion. Because old aragonite, bulk mineralogy bottom sediments has very much since marked by distinct changes chemical composition carbonate. After glacial interval (LGI), large amount endogenic moisture fi lled pluvial lakes Great Basin LGI diminished, apparently abandoned