Abstract The Cretaceous oceanic crust of the Caribbean plate has a long and complex tectonic history as an indentor plate bounded by transcurrent faults (N and S) and subduction margins (W [east slab dip] and E [west slab dip]) with no strain data. Miocene forearc sediments and accreted ophiolites are exposed along the central Pacific coast of Costa Rica and preserve a variety of folding and faulting styles. These clastic sediments, deposited in the forearc as the Middle America trench evolved, contain calcite cements and are cross cut by calcite veins. Analysis of the mechanical twins in these two calcite groups (8 samples, n = 267 twins) at Punta Dominical and the Nicoya Peninsula ophiolite preserve a consistent sub-horizontal shortening strain that is oriented parallel to the current trench axis, as are most of the accretion-related fold axes. Differential stress magnitudes for the calcite twinning strain average −450 bars, and there is little evidence of a twinning strain overprint (low NEVs). Obduction along the Middle America trench involves, in part, a component of trench-parallel horizontal shortening. The Motagua fault originates in the Middle America trench and strikes east as the northern boundary of the Caribbean plate as a sinistral margin. The Roatan Islands are a series of islands composed of south-dipping rocks along the southern side of the Motagua fault. Recent, deformed clastic sediments are drapped over gneisses, schists (40Ar-39Ar biotite age of 14 Ma), conodont-free marbles and ophiolitic fragments of presumed Cretaceous age. Twinning studies (n = 6 samples, n = 425 twins) of these marbles preserve a N–S, horizontal shortening strain, normal to the sinistral plate boundary. Differential stress magnitudes for the calcite twinning strain average −36 MPa. Only in a combined sample (n = 189 grains) is a strain overprint (high NEVs; n = 47) present, which records horizontal shortening strain at 132°, 5°. Jamaica is also along the eastern Motagua fault (Cayman trough) and twinning strain studies in Eocene limestones and younger calcite veins (n = 4 samples; n = 136 twins) preserve a horizontal shortening strain normal to the sinistral plate boundary. Twinning strain results are compared to regional GPS, focal mechanism and SKS anisotropy results around the Caribbean plate, especially along the Middle America trench on the western margin of Costa Rica with some new insights into subduction dynamics.

中文翻译：

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沿中美洲海沟、哥斯达黎加和莫塔瓜左旋断层、洪都拉斯和牙买加的方解石孪晶织物：对加勒比板块的构造影响

摘要 加勒比板块白垩纪大洋地壳作为一个以横流断层（N 和 S）和俯冲边缘（W [东板倾角] 和 E [西板倾角]）为界的压痕板块，具有悠久而复杂的构造历史，没有应变。数据。中新世弧前沉积物和增生蛇绿岩沿哥斯达黎加太平洋中部海岸出露，并保留了各种褶皱和断层样式。这些碎屑沉积物随着中美洲海沟的演化而沉积在弧前，含有方解石胶结物并被方解石脉横切。对 Punta Dominical 和 Nicoya 半岛蛇绿岩这两个方解石组（8 个样品，n = 267 双胞胎）中的机械孪晶的分析保持一致的亚水平缩短应变，其平行于当前的海沟轴取向，大多数与吸积相关的折叠轴。方解石孪晶应变的差异应力大小平均值为 -450 条，几乎没有孪晶应变叠加的证据（低 NEV）。沿中美洲海沟的俯冲部分涉及海沟平行水平缩短的组成部分。莫塔瓜断层起源于中美洲海沟，向东作为加勒比板块的北边界作为左旋边缘。罗阿坦群岛是由沿莫塔瓜断层南侧向南倾斜的岩石组成的一系列岛屿。最近，变形的碎屑沉积物覆盖在片麻岩、片岩（40Ar-39Ar 黑云母年龄为 14 Ma）、无牙形石大理石和推测白垩纪的蛇绿岩碎片上。对这些大理石的孪生研究（n = 6 个样本，n = 425 双胞胎）保留了 N-S、水平缩短应变，垂直于左旋板块边界。方解石孪晶应变平均 -36 MPa 的微分应力大小。仅在组合样品（n = 189 粒）中存在应变叠印（高 NEV；n = 47），其记录了 132°、5° 处的水平缩短应变。牙买加也沿着东部 Motagua 断层（开曼海槽）和始新世石灰岩和年轻方解石脉（n = 4 样本；n = 136 双胞胎）的孪生应变研究保留了垂直于左旋板块边界的水平缩短应变。孪生应变结果与加勒比板块周围的区域 GPS、震源机制和 SKS 各向异性结果进行了比较，特别是在哥斯达黎加西部边缘的中美洲海沟沿线，对俯冲动力学有一些新的见解。仅在组合样品（n = 189 粒）中存在应变叠印（高 NEV；n = 47），其记录了 132°、5° 处的水平缩短应变。牙买加也沿着东部 Motagua 断层（开曼海槽）和始新世石灰岩和年轻方解石脉（n = 4 样本；n = 136 双胞胎）的孪生应变研究保留了垂直于左旋板块边界的水平缩短应变。孪生应变结果与加勒比板块周围的区域 GPS、震源机制和 SKS 各向异性结果进行了比较，特别是在哥斯达黎加西部边缘的中美洲海沟沿线，对俯冲动力学有一些新的见解。仅在组合样品（n = 189 粒）中存在应变叠印（高 NEV；n = 47），其记录了 132°、5° 处的水平缩短应变。牙买加也沿着东部 Motagua 断层（开曼海槽）和始新世石灰岩和年轻方解石脉（n = 4 样本；n = 136 双胞胎）的孪生应变研究保留了垂直于左旋板块边界的水平缩短应变。孪生应变结果与加勒比板块周围的区域 GPS、震源机制和 SKS 各向异性结果进行了比较，特别是在哥斯达黎加西部边缘的中美洲海沟沿线，对俯冲动力学有一些新的见解。牙买加也沿着东部 Motagua 断层（开曼海槽）和始新世石灰岩和年轻方解石脉（n = 4 样本；n = 136 双胞胎）的孪生应变研究保留了垂直于左旋板块边界的水平缩短应变。孪生应变结果与加勒比板块周围的区域 GPS、震源机制和 SKS 各向异性结果进行了比较，特别是在哥斯达黎加西部边缘的中美洲海沟沿线，对俯冲动力学有一些新的见解。牙买加也沿着东部 Motagua 断层（开曼海槽）和始新世石灰岩和年轻方解石脉（n = 4 样本；n = 136 双胞胎）的孪生应变研究保留了垂直于左旋板块边界的水平缩短应变。孪生应变结果与加勒比板块周围的区域 GPS、震源机制和 SKS 各向异性结果进行了比较，特别是在哥斯达黎加西部边缘的中美洲海沟沿线，对俯冲动力学有一些新的见解。