Kinematic history of the Laramide orogeny in latitudes 35°–49°N, western United States
Kinematic history of the Laramide orogeny in latitudes 35°–49°N, western United States
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DOI：
10.1029/98tc02698
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发表时间：
1998-10
期刊：
影响因子：
4.2
通讯作者：
P. Bird
中科院分区：
文献类型：
--
作者：
P. Bird
落基山前陆和邻近地区的运动学历史可追溯到 85 Ma，几乎使用了文献中的所有结构、古地磁和应力数据。通过加权最小二乘法将连续速度场拟合到每个时间步长中的数据，并且该速度随时间进行积分。正如 Hamilton [1981] 提出的，科罗拉多高原的净运动是围绕德克萨斯州北部的一根极点顺时针旋转；但旋转比一些人根据古地磁学推断的要小（3°）。拉拉米德造山运动发生在 75–35 Ma 期间，科罗拉多高原峰值速度在 60–55 Ma 期间为 1.5 mm yr−1。在造山运动的大部分时间里，前陆速度的平均方位角和前陆缩短的平均方向稳定在40°，在50-40 Ma期间增加到55°；先前一些作者提出的逆时针旋转缩短方向是不正确的。将计算出的前陆流速和方向的历史与库拉板块和法拉隆板块的已知运动进行比较，证实了拉拉米德造山运动与早期塞维尔造山运动具有不同的机制：它是由水平俯冲期间的基底牵引力驱动的，而不是由海岸俯冲或西部山脉扩张或地体向海岸增生引起的边缘力驱动的。暂时，50 Ma 缩短方向的小顺时针旋转可能会记录俯冲板片内活跃的库拉-法拉隆变换的通过。
The kinematic history of the Rocky Mountain foreland and adjacent areas is computed back to 85 Ma, using virtually all the structural, paleomagnetic, and stress data in the literature. A continuous velocity field is fit to the data in each time step by weighted least squares, and this velocity is integrated back through time. As proposed by Hamilton [1981], the net movement of the Colorado Plateau was a clockwise rotation about a pole in northern Texas; but the rotation was less (3°) than some have inferred from paleomagnetism. The Laramide orogeny occurred during 75–35 Ma, with peak Colorado Plateau velocities of 1.5 mm yr−1 during 60–55 Ma. The mean azimuth of foreland velocity and mean direction of foreland shortening was stable at 40° for most of the orogeny, increasing to 55° in 50–40 Ma; the counterclockwise rotation of shortening directions proposed by some previous authors is incorrect. Comparing the computed histories of foreland flow speed and direction with the known motions of the Kula and Farallon plates confirms that the Laramide orogeny had a different mechanism from the early Sevier orogeny: it was driven by basal traction during an interval of horizontal subduction, not by edge forces due to coastal subduction or the spreading of the western cordillera or by accretion of terranes to the coast. Tentatively, a minor clockwise rotation of shortening directions at 50 Ma may record the passage of an active Kula‐Farallon transform within the subducted slab.