Flexural Subsidence Around Ross Island, West Antarctica
Flexural Subsidence Around Ross Island, West Antarctica
复制标题
DOI：
10.1029/2021gc010181
复制
发表时间：
2022-03
期刊：
影响因子：
3.7
通讯作者：
S. Jha;D. Harry;C. P. Wenman;M. Mayle
中科院分区：
文献类型：
--
作者：
S. Jha;D. Harry;C. P. Wenman;M. Mayle
罗斯岛位于维多利亚陆地盆地南部，沿着西南极裂谷系的西缘。自约以来的幕式火山作用。4.6马云在岛屿周围形成了一条不连续的沉积护城河，与区域扩张同步。护城河是由四个较小的子盆地在不同的火山活动时期形成的复合体。每个子盆地内的沉降被建模为连续弹性板的弯曲，首先考虑仅在相关火山活动期间发生的沉降，然后考虑自罗斯岛火山活动开始以来的累积沉降。基于每个子盆地中沉积的地层的模型在相应火山活跃的时间间隔内产生的弯曲刚度范围为6-36 × 1018 N-m，最低值与岛屿南部和西南侧最年轻的火山有关。基于自火山活动开始以来沉积的整个地层间隔的模型产生的弯曲刚度比仅考虑相关火山活动时每个子盆地内沉积的地层的模型大20倍。复合盆地的模型高估了岩石圈的强度，因为包含了在区域伸展而不是局部挠曲主导沉降的时期沉积的地层。这些模型表明罗斯岛处于接近弯曲均衡的状态，上地幔密度较低（3，260 kg m−3），尽管允许额外的浮力负荷相当于地幔温度异常高达200°C。
Ross Island is located in the southern Victoria Land Basin along the western margin of the West Antarctic Rift System. Episodic volcanism since ca. 4.6 Ma produced a discontinuous sedimentary moat around the island, coeval with regional extension. The moat is a composite of four smaller sub‐basins created during distinct episodes of volcanism. Subsidence within each sub‐basin is modeled as bending of a continuous elastic plate, first considering subsidence that occurred only during the time in which the associated volcano was active, and then considering cumulative subsidence since the onset of volcanism on Ross Island. Models based on strata deposited in each sub‐basin during the time interval in which the respective volcano was active yield flexural rigidities ranging from 6–36 × 1018 N‐m, with the lowest values associated with the youngest volcanoes on the south and southwest sides of the island. Models based on the entire stratigraphic interval deposited since the onset of volcanism yield flexural rigidities up to 20 times greater than models that consider only strata deposited within each sub‐basin when the associated volcano was active. Models of the composite basin overestimate the strength of the lithosphere due to inclusion of strata deposited during periods in which regional extension rather than local flexure dominated subsidence. The models indicate that Ross Island is in near flexural isostatic equilibrium with moderately low‐density (3,260 kg m−3) upper mantle, although an additional buoyant load equivalent to a mantle temperature anomaly of up to 200°C is permissible.