Petrography, strontium, barium and uranium concentrations, and strontium and uranium isotope ratios in speleothems as palaeoclimatic proxies: Soreq Cave, Israel
Petrography, strontium, barium and uranium concentrations, and strontium and uranium isotope ratios in speleothems as palaeoclimatic proxies: Soreq Cave, Israel
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DOI：
10.1191/095968399673664163
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发表时间：
1999-11-01
期刊：
影响因子：
2.4
通讯作者：
Kaufman, A
中科院分区：
文献类型：
--
作者：
Ayalon, A;Bar-Matthews, M;Kaufman, A
根据以色列Soreq洞穴洞穴沉积物δ（18）O和δ（13）C的变化，重建了东地中海地区近60 ka BP以来的古气候。60 ~ 17 ka BP（相当于末次冰期）的雾凇期气候条件相对寒冷干燥，而17 ka BP至今气候条件相对温暖湿润。在17 kaBP左右，气候发生了重大变化，8.5 ~ 7.0kaBP期间，年降水量和温度急剧增加，并出现了一个非常湿润的时期。在较冷和干燥的时期，大的，无碎屑，优先取向的方解石晶体沉积从缓慢移动的水。由于水文制度的急剧变化，在类似17 ka BP，快速移动的水开始夹带的土壤和携带碎屑物质进入洞穴，方解石晶体沉积变得很小，上反角。与岩相学和同位素变化相一致的是，锶、钡和铀的浓度以及Sr-87/Sr-86和（U-234/U-238）（0）的比值急剧下降，在最潮湿的时期达到最小值。这种下降反映了土壤白云岩寄主岩石的风化作用增强。在较冷和干燥的时期，较高的微量元素浓度和较高的同位素比值反映了增加的贡献，来自外源（海喷雾和风尘）的盐，和减少的贡献风化从主机花岗岩。
The reconstruction of the palaeoclimate of the eastern Mediterranean region for the last 60 ka BP is based on the delta(18)O and delta(13)C variations of speleothems from Soreq Cave, Israel. Climatic conditions during most of the rime interval between 60 and 17 ka BP (the period equivalent to the last glacial) were relatively cold and dry, while they were warmer and wetter from 17 ka BP to the present. At similar to 17 ka BP, there was a major climatic change with a sharp increase in annual rainfall and temperature and a very wet period occurring between 8.5 and 7.0 ka BP. During the colder and drier period, large, detritus-free, preferentially oriented calcite crystals were deposited from slow-moving water. As a result of a sharp change in the hydrological regime at similar to 17 ka BP, fast-moving water started entrainment of the soil and carrying detrital material into the cave, and the calcite crystals deposited became small and anhedral. Coinciding with the petrographic and isotopic changes, a sharp drop occurred in the concentrations of strontium, barium and uranium, and in the ratios Sr-87/Sr-86 and (U-234/U-238)(0), which reached mini mum values during the wettest period. This drop reflects enhanced weathering of the soil dolomite host rock. During colder and drier periods, higher trace-element concentrations and higher isotopic ratios reflect an increase in the contribution of salts derived from exogenic sources (sea spray and aeolian dust), and a reduced contribution of weathering from the host dolomites.