ABSTRACT

Uplifted coastal terraces are present on Santa Catalina Island, but so poorly preserved that researchers have debated for more than a century whether they even exist. Morphometric analyses of LIDAR-based topography on the California Channel Islands suggest that the poor expression of terraces on Catalina Island is due a combination of (1) geological conditions less conducive to terrace formation than on the other Channel Islands and (2) high landslide susceptibility around Catalina’s coastal margin that is erasing terrace morphology and deposits before they can reach the island's relatively un-dissected interior. Both of these factors seem to be related to the mechanical properties of the island’s predominant rock type, the Catalina Schist. Several of the other Channel Islands – such as Santa Barbara, San Clemente, Anacapa, and San Miguel Islands – have topography that is dominated by their terrace morphology, mostly by virtue of the small size of those islands. Of the large islands, Santa Rosa has the most extensive terraces, apparently driven by the prevalence of shallowly dipping sedimentary rock. Looking at terrace preservation generally, subhorizontal sedimentary units seem to represent an optimum between promoting the initial creation of wide terrace platforms and resistance to terrace erosion thereafter.

摘要

圣卡塔利娜岛上存在隆起的沿海梯田，但保存得如此糟糕，以至于研究人员已经争论了一个多世纪，它们是否存在。加利福尼亚海峡群岛基于激光雷达的地形的形态测量分析表明，卡塔利娜岛梯田的不良表现是由于（1）地质条件比其他海峡群岛更不利于梯田形成和（2）滑坡敏感性高在卡塔利娜海岸边缘附近，梯田形态和沉积物在到达岛上相对未被剖析的内部之前就已经被抹去。这两个因素似乎都与岛上主要岩石类型卡塔利娜片岩的机械特性有关。其他几个海峡群岛——如圣巴巴拉、圣克莱门特、阿纳卡帕、和圣米格尔群岛——地形以梯田形态为主，主要是因为这些岛屿面积小。在大岛中，圣罗莎拥有最广阔的梯田，这显然是由浅倾沉积岩的普遍存在所驱动的。从一般的阶地保护来看，亚水平沉积单元似乎代表了促进宽阶地平台的初始创建和之后的阶地侵蚀抵抗之间的最佳选择。