Apatite (U – Th)/He age constraints on the Mesozoic and Cenozoic evolution of the Bathurst region, New South Wales: evidence for antiquity of the continental drainage divide along a passive margin
Apatite (U – Th)/He age constraints on the Mesozoic and Cenozoic evolution of the Bathurst region, New South Wales: evidence for antiquity of the continental drainage divide along a passive margin
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DOI：
10.1080/08120090600923303
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发表时间：
2006-12
影响因子：
1.2
通讯作者：
C. Persano;P. Bishop;F. Stuart
中科院分区：
文献类型：
--
作者：
C. Persano;P. Bishop;F. Stuart
结合磷灰石（U-Th）/He和裂变径迹热年代计，对新南威尔士州巴瑟斯特地区中新生代剥蚀历史进行了约束。大陆分水岭上新的磷灰石（U-Th）/He年龄介于83 ± 14 ~ 114 ± 18 Ma（±2σ）之间，支持了以前发表的磷灰石裂变径迹（AFT）数据的证据，即该地区在白垩纪中期经历了一个快速剥蚀期。磷灰石He衍生的热历史限制在该地区的侵蚀量，并建议在剥蚀的巴瑟斯特岩的空间变化对应于三个广泛的区域具有不同的历史。大陆水系分水岭的区域将东侧与西侧分开，东侧在120 - 90 Ma时剥蚀迅速，约3 000万年后，超过3公里的地壳被移走，西侧剥蚀不太迅速，也不太突出。一些AFT和He年龄与大陆伸展和塔斯曼海开放的时间相吻合，表明大陆分水岭以东的快速剥蚀与裂谷过程有关。这样的解释意味着，东部蓝山边界的悬崖不是在裂谷期形成的，可能是一个较晚的地形特征，与早期构造特征的折返有关和/或与中生代后构造活动有关。大陆分水岭以西地区的演变特点是剥蚀率高于高原其他地区，但低于巴瑟斯特地区东侧。这种模式的原因尚不清楚。拉克伦褶皱带的断层有可能在白垩纪伸展期及以后被重新激活，但没有断层穿过岩基。总的来说，这些数据意味着巴瑟斯特地区的大陆边缘是由固定在大陆分水岭上的高原下穿作用演化而来的。这反过来意味着大陆分水岭是一个长期存在的地形特征，可以追溯到塔斯曼海分裂之前。
The apatite (U – Th)/He and fission track thermochronometers are combined to constrain the Mesozoic and Cenozoic denudational history of the Bathurst region in New South Wales. New apatite (U – Th)/He ages across the continental drainage divide range from 83 ± 14 to 114 ± 18 Ma (±2σ), supporting the evidence from previously published apatite fission track (AFT) data that the region underwent a period of rapid denudation during the mid-Cretaceous. The apatite He-derived thermal histories constrain the amount of erosion in the area and suggest that spatial variations in denudation of the Bathurst Batholith correspond to three broad regions with different histories. The area of the continental drainage divide separates the eastern flank where denudation was rapid at 120 – 90 Ma, and >3 km of crust was removed in about 30 million years, from the western flank, where denudation was less rapid and less prominent. The coincidence of some of the AFT and He ages with the timing of continental extension and Tasman Sea opening suggests that the rapid denudation east of the continental drainage divide was associated with the rifting processes. Such an interpretation means that the escarpment that bounds the Blue Mountains on the east was not formed at the time of rifting and may be a later topographic feature, connected with exhumation of an earlier structural feature and/or related to post-Mesozoic tectonic activity. The evolution of the area west of the continental drainage divide is characterised by rates of denudation higher than on the rest of the plateau but lower than on the eastern flank in the Bathurst area. The reason for this pattern is still unclear. It is possible that faults of the Lachlan Fold Belt were reactivated during the Cretaceous extension and later, but no faults are mapped across the batholith. Overall, the data imply that the continental margin in the Bathurst region evolved by plateau downwearing pinned to the continental drainage divide. This means in turn that the continental drainage divide is a longstanding topographic feature, dating from before Tasman Sea breakup.