Color Index And Evolution Of Palaeoclimate In Suqian City Area Since Late Pleistocene

Suqian,located in the northern part of Jiangsu Province,is the transition zone of hilly country to Subei Basin.Its sedimentary evolution including sea facies and continental facies comprising deepwater and shallow water depositional environment.Climate change is obviously since the Quaternary, especially the late Pleistocene. sediments,responding to climate change, contain a wealth of information about ancient climate and environment. In the sediments, color change is the most intuitive characteristic, and reflects the ancient climate and environment. Therefore, relying on "standard drilling exploration and Quaternary strata standard profile set up" in "Suqian City active fault detection and seismic risk evaluation" project taken charge by Jiangsu Seismological Bureau and Suqian City Seismological Bureau suggests its sedimentary environment Suqian City neighborhood since the late Pleistocene and paleoclimatic change by color index amplitude and frequency change, combined with pollen, magnetic susceptibility and granularity climate assistant index.According to the chrominance amplitude variation from top 71.5m of BK2 drilling sediments, combined with lithological characterization, particle size curve congregation, pollen curve, magnetic susceptibility curve, the depth of the deposit is divided into seven sections. Segment Ⅰ, Ⅱ, Ⅲ,Ⅳsegment corresponds to the upper part of the Pleistocene, the Ⅴ, Ⅵ,Ⅶ segment corresponds to the Holocene, the bottom boundary of each segment is 50.6m, 53.5m,37.5m, 27 m, 20.8m, 15.8m, 6.0m. Understanding the relationship the color index and deposition of mineral and other ingredients, such as brightness L * and calcium carbonate, redness a * and hematite, yellowness b * and goethite, chromaticity as the study of ancient climate and environment of proxies, speculates sedimentary environment and paleoclimate. Its analysis results indicate hydrodynamic conditions as a whole is high energy to low energy, sedimentary environments are shallow alluvial deposition to deep lacustrine sedimentary, climatic evolution includes six sequence evolution(warm and humid- warm slightly dry- cold and wet- cool and dry- warm and humid- cool and wet). Compared with and the study of climate evolution in the study area five sections pollen period, color indicators six division is used to reflect climate evolution sequence as the study of the period.By contrast with the Emilian deep sea oxygen isotope curve and Luochuan and Zhenjiang Chittagong loess magnetic susceptibility curve obtained the paleoclimatic change of BK2 hole study period since the late Pleistocene sediments is consistent with global climate and regional climate characteristics, and own uniqueness.