Lake level changes in Hala Lake(NW China) based on ostracodassemblages during the LGM and Post-LGM

The Hala Lake, located in the Qilian Mountains, Qinghai Province, China, at 4078 m a.s.l. may archive in its sediments hydrological and climate changes during the Late Quaternary time, as it is close to the area impacted by the East-Asian Summer monsoon and westerly-driven air masses. Based on the sediment core H7, which was taken in the center of the lake at 65m water depth,ostracod assemblages and stable isotopes from ostracode shells were investigated in details. Three main species were found, which are common species in high altitude saline lakes of the Tibetan Plateau: Leucocythere sp.,Limnocythereinopinata and Eucypris sp.They started to occur in deeper part of H7,indicating an early onset of favorable living conditions during the LGM and post-LGM periods. Besides, algae occurred between 25 and 32m water depth. According to the unevenly distributed amount of ostracods and oxygen isotope data, our results indicate important lake level changes during the global LGM and Lateglacial. The lake experienced lowest levels of 25-50 m below the present water line. Ostracods disappeared with the onset of the early Holocene.A stepwise refilling started already at ca. 16 kyr BP and reached -25 m level during the Bølling/Allerød warm phase at ca. 13.5 kyr BP.Latest at ca.7.6 kyr BP, the lake reached a stable highstand similar to the present level until ca.6 kyr BPas . The subsequent lake development remains unclear due to strong mismatches of the data but may indicate a general trend to deteriorating conditions and lake level lowstands at ca. 5.0-4.2, 2.0 and at around 0.5 kyr BP.; Ostracods Distribution in H2 ; Ostracods plate in Hala lake