Spectra Alalysis Of Early-Pleistocene Latchstring High-Resolution Climatic Record In Lixia Basin

To access a reliable, precise and high-resolution time-scale is a challenging task in the reconstruction of palaeo-environment at Pleistocene period. Five highly precise time scales of Pleistocene have been established and been accepted in the researches of past globle till now: (1) The time-scale spanning over 80 ten thousand years, that Imbrie etc (1984)build, namely famous SPECMAP's time-scale;(2) The high-resolution time-scale spanning over 30 ten thousand years of Indian Ocean, that Martinson etc (1987) build;(3) The long time-scale spanning over 2.8 Myr, that Ruddiman etc (1989) and Raymo etc (1989) build on DSDP site 607 of the North Atlantic;(4) The long time-scale spanning over 2. 6 Myr, that Shackleton etc (1990) build on DSDP site 607 of the equator Pacific;(5) The long time-scale spanning over 2. 5 Myr who possesses higher resolution and the precision, and was built by Ding Zhongli (1994) on Baoji section of the Loess-plateau . These 5 time-scales chiefly come from deep sea deposit and the loess record , but lakes and its river basins are the natural syntheses of relative independence , and are connection point of layers' interaction , thedeposit records in lakes are the optimum information carriers that reflect palaeoclimate construction and the environment evolution.A 84 m thick typical lacustrine deposit with high depositional rate near Dongshanding Village in Linxia Basin, Gansu Province, Northwest China, with silt and clayey silt is given first place to , spans 2. 35—1. 65 MaB. P. through ancient geomagnetism and amino acid survey year. We has been in progress the systematic sampling at an interval with 2. 5cm , and up to now , established a high-resolution time scale in obtained for the first time by using orbital tuning approach from the carbonate contents;this paper discusses carbonate contents period evolution by spectrum analysis technique and makes the following preliminary conclusions:Based on the high-resolution orbitally-tuned time-scale, the spectrum analysis results also show that at the period of 2. 35—1- 65 Ma B.P., the paleoclimate had an clear 117 K dominant periodicity, suggesting that the earth' s eccentricity change was the main cause of climate change over this period.The time-scale indicates that climate change of during 1.75 - 1. 8Ma B. P. was its coldest and moist period in early Pleistocene, and this time, the high surface of the palaeo-lake in Dongshan-dinghad appeared . This cold event is believed occurred popular in China during Early-Pleistoncene period, with consequences of the large-scaled sea-intrusion at Eastern China during that time.