Cenozoic Exhumation of Larsemann Hills,East Antarctica:Evidence from Apatite Fission-track Thermochronology

Does Cenozoic exhumation occur in the Larsemann Hills, East Antarctica？ In the present paper, we conducted an apatite fission-track thermochronologic study across the Larsemann Hills of East Antarctica. Our work reveals a Cenozoic exhumation event at 49.8 ± 12 Ma, which we interpret to be a result of exhumation caused by crustal extension. Within the uncertainty of our age determination, the timing of extension in East Antarctica determined by our study is coeval with the onset time of rifting in West Antarctica at c.55 Ma. The apatite fission-track cooling ages vary systematically in space, indicating a coherent block rotation of the Larsemann Hills region from c.50 Ma to c.10 Ma. This pattern of block tilting was locally disrupted by normal faulting along the Larsemann Hills detachment fault at c.5.4 Ma. The regional extension in the Larsemann Hills, East Antarctica was the result of tectonic evolution in this area, and may be related to the global extension. Through the discussion of Pan-Gondwanaland movement, and Mesozoic and Cenozoic extensions in West and East Antarctica and adjacent areas, we suggest that the protracted Cenozoic cooling over the Larsemann Hills area was caused by extensional tectonics related to separation and formation of the India Ocean at the time of Gondwanaland breakup.

拉斯曼丘陵新生代剥露作用的裂变径迹证据

在西南极和横贯南极山脉地区，新生代裂谷和剥露作用非常普遍。但是，文献中很少记录东南极地区的新生代剥露作用。文中根据东南极普里兹湾拉斯曼丘陵地质样品的磷灰石裂变径迹年龄和热历史的模拟，认为在东南极海岸边缘存在新生代的隆升和伸展作用，其年龄为始于（49．8±12）Ma。该年龄略晚于西南极裂谷系的启动年龄（约60-50Ma）。由于差异隆升作用，在拉斯曼丘陵地区发育了更新的正断层作用——拉斯曼丘陵拆离断层的新活动，其年龄为约5．4Ma。东南极周缘新生代裂谷和伸展作用的普遍存在，是冈瓦纳裂解以来大陆分离和印度洋形成的结果。