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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >A plume model of transient diachronous uplift at the Earth's surface
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A plume model of transient diachronous uplift at the Earth's surface

机译：地球表面瞬时历时隆升的羽状模型

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Convection in the Earth's mantle appears to be strongly time-dependent on geological time scales. However, we lack direct observations which would help constrain the temporal variation of convection on time scales of 1-10 Ma. Recently, it has been demonstrated that transient uplift events punctuated the otherwise uniform thermal subsidence of sedimentary basins which fringe the Icelandic plume. In the Faroe-Shetland basin, three-dimensional seismic reflection surveys calibrated by well logs have been used to reconstruct a similar to 55 million year old transient event. The minimum amount of uplift is 490 m, which grew and decayed within 2 Ma. This event has also been mapped 400 km further east in the North Sea basin, where peak uplift with an amplitude of 300 m occurred 0.3-1.6 Ma later. Neither observation can be explained by glacio-eustatic sea-level changes or by crustal shortening. We describe a simple fluid dynamical model which accounts for these transient and diachronous observations. In this model, we assume that the Icelandic plume was already in existence and that it had an axisymmetric geometry in which hot (e.g. 1400 degrees C) asthenospheric material flows away from a central conduit within a horizontal layer. A transient temperature anomaly introduced at the plume centre flows outward as an expanding annulus. Its geometry is calculated using radial flow between two parallel plates with a Poiseuille cross-stream velocity profile. The expanding annulus of hot asthenosphere generates transient isostatic uplift at the Earth's surface. Stratigraphic observations from both basins can be accounted for using a plume flux of 1.3 x 10(8) km(3) Ma(-1) for a layer thickness of 100 km. Plume flux is broadly consistent with that required to account for Neogene (0-20 Ma) V-shaped ridges south of Iceland, although our transient temperature anomalies are larger. We suspect that the stratigraphic expression of transient convective behaviour is common and that a careful examination of appropriate records could yield important insights.
机译：地球地幔中的对流似乎在很大程度上取决于地质时标。但是，我们缺乏直接的观测资料，这有助于在1-10 Ma的时间尺度上限制对流的时间变化。近来，已经证明，短暂的隆升事件刺穿了沉积在冰岛羽状边缘的沉积盆地，否则，它们的热沉降就会均匀。在法罗-设得兰群岛盆地，通过测井仪校准的三维地震反射勘测已用于重建类似5500万年前的瞬变事件。最小隆起量为490 m，其在2 Ma之内生长和衰减。该事件也被绘制在北海盆地以东400公里处，在0.3-1.6 Ma之后出现了300 m振幅的峰值隆起。这两种观测都不能用冰川-冰川消融的海平面变化或地壳缩短来解释。我们描述了一个简单的流体动力学模型，该模型考虑了这些瞬态和历时性观测。在此模型中，我们假设冰岛羽状流已经存在，并且具有轴对称的几何形状，其中热（例如1400摄氏度）的软流圈材料从水平层内的中心导管流走。在羽流中心引入的瞬态温度异常作为扩张的环空向外流动。它的几何形状是使用两个平行板之间的径向流动（具有Poiseuille横流速度分布）计算的。热流软流圈的膨胀环在地球表面产生瞬时的等静力上升。来自两个盆地的地层观测可以解释为使用1.3 x 10（8）km（3）Ma（-1）的羽流，层厚为100 km。尽管我们的瞬态温度异常较大，但羽流通量与解释冰岛南部新近纪（0-20 Ma）V形脊所需的通量大致一致。我们怀疑瞬态对流行为的地层学表达很普遍，并且仔细检查适当的记录可能会得出重要的见解。

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