Cosmogenic 36Cl geochronology of late Quaternary glaciers in the Bolkar Mountains, south central Turkey

We present the first quantitative late Quaternary cosmogenic 36Cl glacial geochronology from the Bolkar Mountains of south central Turkey. Thirty samples were collected from three glaciated valleys. The geomorphological investigations indicate that the palaeoglaciers deposited their moraines between 3200 and 2200 m above sea level on the north- and south-facing valleys. We recognize four glacial periods, with the oldest one dating back to about 46.0±7.0 ka in the northern Karagöl Valley. Later, glaciers reached their maximum positions (∼5.5 km from cirque to snout) by 18.9±3.3 ka (during the local Last Glacial Maximum; LGM) in the Karagöl Valley. Late-glacial moraines were dated to between 15.2±1.6 and 12.6±2.3 ka in both northern Alagöl and southern Elmalı Valleys, respectively. The final deglaciation in the mountain commenced in the early Holocene (9.0±0.9 ka in the Karagöl Valley; 8.5±1.8 ka in the Elmalı Valley). A contemporaneous outwash plain dates to 8.4±1.0 ka at the outlet of the Alagöl Valley. Our results agree well with the glacial chronologies obtained from other Turkish and Mediterranean mountains.本研究首次报道了土耳其中南部博卡尔山脉（Bolkar Mountains）晚第四纪宇宙成因36Cl（cosmogenic ³⁶Cl）定量冰川地质年代学数据。研究团队从3条冰川谷中共采集30件样品。地貌学调查显示，古冰川在南北朝向的谷地上，于海拔3200~2200米区间堆积了冰碛物。本次研究识别出4期冰川作用，最古老的一期可追溯至北卡拉戈尔谷（Karagöl Valley）的约46.0±7.0 ka。后续在卡拉戈尔谷，冰川于18.9±3.3 ka（对应区域末次冰盛期，Last Glacial Maximum, LGM）时达到最大规模，冰斗至冰舌末端的距离约5.5 km。北阿拉戈尔谷（Alagöl Valley）与南埃尔马利谷（Elmalı Valley）的冰消晚期冰碛物年代分别为15.2±1.6 ka与12.6±2.3 ka。该山地的最终冰退作用始于早全新世：卡拉戈尔谷为9.0±0.9 ka，埃尔马利谷为8.5±1.8 ka。阿拉戈尔谷出口处的同期冰水沉积平原年代为8.4±1.0 ka。本研究结果与土耳其境内及地中海其他山地所获冰川地质年代序列吻合度较高。