Boron Element Quantitatively Reconstruct Paleosalinity And Paleoclimatic Research

The purpose of PAGES research is to attain and explain all kinds of paleoclimatic record information, recognize global system changes process and mechanism. The PAGES research make it possible to provide basal data for establishing future environmental changes model and efficiently decrease indetermination in prediction. The key and difficulty is climate factor's reconstruction. Exact prediction need climate factor's research to be quantitative which is an important aspect in PAGES researchPaleosalinity reconstruction is an essential method to reestablish climate, recognize climate changes process and principle . Paleosalinity reconstruction could identify regional climate changes from regional salinity changing history. At present common methods include: paleobiological geography data qualitatively describe water salinity; Isotope and microelement geochemistry methods quantitatively divide water salinity; Hole liquid or fluid inclusion directly measure salinity; Phosphate and clay minerals data qualitatively calculate paleosalinity .Many experts have been study and apply boron element in sediment to quantitatively reestablish paleosalinity. We can use boron in sediment to reestablish paleosalinity and analyze regional sediment and geography evolvement character; climate changing character; discuss basin natural gas formation and evaluate basin oil and natural gas resources. The Boron element method for reestablishing paleosalinity is feasible in contrast with others means (Sr/Ca, phosphate). I use the method to qualitativelyreestablish Gahai lake sediment core paleosalinity and discuss climate and environment changes in Gahai region since 8000 aBP.1. Gahai sediment age indicate that it has a quick sedimentation velocity in 7.12 meter in core(about 6570 aBP). Gravel size data in Gahai lake sediment core are similar with Malan loess. I consider that there is Malan loess in Gahai sediment, which may help explain Gahai lake's quick sedimentation velocity.2. Walker method has a relative limitation, mainly apply in mud rock and divide salt water and fresh water sediment phases. But Couth consider the difference absorbability in clay minerals and the method has a wider application field.3. Paleosalinity,RB/Sr and Carbonate contents show that 8000 aBP paleoclimate changing in Gahai region could be divided into four stages: 7800—4800 aBP warm-wet climate; 4800—2800 aBP cold-dry climate; 2800— 1450 aBP wet climate; Since 1450 aBP paleoclimate has a intensive fluctuation.