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.

我们首次报道了土耳其中南部博尔卡尔山脉的晚第四纪定量宇宙成因36Cl（cosmogenic 36Cl）冰川地质年代学研究。研究团队从3条冰川作用谷中共采集了30件样品。地貌学调查结果显示，古冰川的冰碛物沉积于海拔3200至2200米的南北朝向山谷中。本次研究识别出4次冰川作用旋回，其中最古老的一期可追溯至北侧卡拉戈尔谷（Karagöl Valley）的约46.0±7.0 ka。此后，卡拉戈尔谷的冰川在距今18.9±3.3 ka（对应当地末次冰盛期（Last Glacial Maximum，LGM））时达到最大规模，冰斗至冰舌的间距约5.5 km。北侧阿拉戈尔谷（Alagöl Valley）与南侧埃尔马利谷（Elmalı Valley）的冰消期晚期冰碛物年代分别为15.2±1.6 ka与12.6±2.3 ka。该山地的最终冰消作用始于全新世早期：卡拉戈尔谷的冰消年代为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已获取的冰川年代学序列吻合良好。