Detrital Thermochronometry Reveals That the Topography Along the Antarctic Peninsula is Not a Pleistocene Landscape
Detrital Thermochronometry Reveals That the Topography Along the Antarctic Peninsula is Not a Pleistocene Landscape
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DOI：
10.1029/2019jf005447
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发表时间：
2020-06
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影响因子：
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通讯作者：
A. Clinger;M. Fox;G. Balco;K. Cuffey;D. Shuster
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文献类型：
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作者：
A. Clinger;M. Fox;G. Balco;K. Cuffey;D. Shuster
利用近海碎屑磷灰石（U-Th）/He热年代测定法和流域地形的3D热动力学建模，我们限制了南极半岛布尔乔亚峡湾（AP）主要地形变化的时间。虽然许多中纬度冰川景观的发展主要是为了应对过去2.6 Ma的全球变冷，但我们发现布尔乔亚峡湾的千米级景观演变始于约30-12 Ma前，自约16 Ma以来发生了<2 km的山谷切割。这种早期发生的主要地形变化发生在这个位置的高山冰川作用开始后，并在此之前的区域性多温冰盖的发展推断，从沉积证据近海的AP。我们假设地形变化与（i）不断变化的地形和冰川侵蚀过程之间的反馈，（ii）冰川-间冰期变化的影响，以及（iii）冰下融水的流行。布尔乔亚峡湾长期剥露的时间和推断的空间模式与一个假设一致，即在全球上新世-更新世冷却期间，AP的冰川侵蚀过程受到抑制，而不是增强。我们的研究考察了随着当地气候变冷，冰川过程对全流域侵蚀的长期影响。我们的研究结果支持了这一假设，即不同纬度的景观对全球变冷有不同的反应。我们的研究结果还表明，侵蚀增强沿着布尔乔亚峡湾今天的高原侧翼，这可能是由于冰缘过程或通过冰下冰碛覆盖。如果区域变暖持续，融水变得更加明显，我们预测，增强侵蚀沿着高原侧翼将加速地形变化。
Using offshore detrital apatite (U‐Th)/He thermochronometry and 3D thermo‐kinematic modeling of the catchment topography, we constrain the timing of major topographic change at Bourgeois Fjord, Antarctic Peninsula (AP). While many mid‐latitude glacial landscapes developed primarily in response to global cooling over the last ~2.6 Ma, we find that kilometer‐scale landscape evolution at Bourgeois Fjord began ~30–12 Ma ago and <2 km of valley incision has occurred since ~16 Ma. This early onset of major topographic change occurred following the initiation of alpine glaciation at this location and prior to the development of a regional polythermal ice sheet inferred from sedimentary evidence offshore of the AP. We hypothesize that topographic change relates to (i) feedbacks between an evolving topography and glacial erosion processes, (ii) effects of glacial‐interglacial variability, and (iii) the prevalence of subglacial meltwater. The timing and inferred spatial patterns of long‐term exhumation at Bourgeois Fjord are consistent with a hypothesis that glacial erosion processes were suppressed at the AP during global Plio‐Pleistocene cooling, rather than enhanced. Our study examines the long‐term consequences of glacial processes on catchment‐wide erosion as the local climate cooled. Our findings support the hypothesis that landscapes at different latitudes had different responses to global cooling. Our results also suggest that erosion is enhanced along the plateau flanks of Bourgeois Fjord today, which may be due to periglacial processes or mantling via subglacial till. If regional warming persists and meltwater becomes more pronounced, we predict that enhanced erosion along the plateau flank will accelerate topographic change.