We report on a series of small-scale, en-échelon faults in limestone (Les Matelles, France) that result in the formation of a series of linked pull-aparts (en-échelon pull-apart arrays) that have been infilled with calcite. The formation of stylolite seams and isolated veins occurs adjacent to these fault zones, which constrain the direction of minimum infinitesimal stretching axis (commonly interpreted as maximum compressional stress). We observe that en-échelon pull-apart arrays occur when the maximum infinitesimal shortening direction is at 55° or greater to the enveloping surfaces of the en-échelon fault arrays. This situation differs from en-échelon vein arrays, in which the maximum horizontal infinitesimal shortening direction occurs at 55° or less to the enveloping surfaces. We interpret these features with respect to transpressional strain modeling, which distinguishes between wrench (simple shear) dominated transpression and pure shear dominated transpression. Pure shear dominated transpression occurs if the maximum infinitesimal shortening direction is at 55° or greater to the enveloping surfaces, and results in a maximum infinitesimal stretching direction that is vertical. The formation of en-échelon vein arrays with vertical enveloping surfaces require a horizontal infinitesimal stretching direction, which is incompatible with pure shear dominated transpression. Rather, en-échelon pull-apart arrays form to accommodate the wrench component of deformation in pure-shear dominated transpression.

我们报告了石灰岩（法国 Les Matelles）中的一系列小规模的梯形断层，这些断层导致形成了一系列已填充方解石的连接拉断层（ en-échelon拉断阵列） . 在这些断裂带附近形成了缝合线缝和孤立脉，这限制了最小无限小的拉伸轴（通常解释为最大压缩应力）的方向。我们观察到，当最大极小缩短方向与梯级断层阵列的包络面成 55° 或更大时，会出现梯级拉开阵列。这种情况不同于en-échelon脉阵列，其中最大的水平无穷小缩短方向出现在与包络面成 55° 或更小的角度。我们根据横压应变建模来解释这些特征，该模型区分了扳手（简单剪切）主导的横压和纯剪切主导的横压。如果最大极小缩短方向与包络面成 55° 或更大，则会发生纯剪切主导的横压，并导致最大极小拉伸方向是垂直的。具有垂直包络面的梯状脉阵列的形成需要水平的无限小的拉伸方向，这与纯剪切主导的挤压不相容。相反，en-échelon拉开阵列形成以适应纯剪切主导的挤压变形的扳手分量。