ABSTRACT

Along the south coast of the North Island of New Zealand, elevated Pleistocene marine terraces provide evidence for vertical deformation associated with active crustal faults and the westward subduction of the Pacific Plate at the southern Hikurangi margin. We have reassessed the age and elevation of these terraces. Optically Stimulated Luminescence (OSL) data of their cover bed sediments (20 new ages) provide the first numerical ages for most of these terraces. Shore platform elevations have been surveyed using differential Global Navigation Satellite System (GNSS) measurements of the wave-cut bedrock straths underlying these terraces. These new data allow the terraces to be temporally correlated across the margin. Seven different-aged terraces were identified and mapped along the Wellington south coast; these are preserved discontinuously between the westernmost site at Tongue Point, and Ngawi near Cape Palliser, to the east. The OSL data indicate that most of these terraces formed at MIS 5a, 5c, 5e (Last Interglacial) and 7a. The terraces are best preserved within the Hikurangi margin forearc, where they decrease in altitude towards the west, indicating long wavelength, westward tectonic tilting. The terraces are locally offset by a number of active crustal faults, most notably the Wairarapa and Ohariu faults.

摘要

沿着新西兰北岛的南海岸，升高的更新世海洋阶地提供了与活动地壳断层相关的垂直变形和 Hikurangi 南部边缘太平洋板块向西俯冲的证据。我们重新评估了这些梯田的年龄和海拔。其盖床沉积物（20 个新时代）的光致发光 (OSL) 数据为这些阶地中的大多数提供了第一个数字年龄。使用差分全球导航卫星系统 (GNSS) 测量这些平台下的波切基岩层，对海岸平台高程进行了调查。这些新数据允许梯田在边缘上具有时间相关性。沿惠灵顿南海岸确定并绘制了七个不同年龄的梯田；这些不连续地保存在舌点的最西端和东部靠近帕利瑟角的 Ngawi 之间。OSL 数据表明，这些阶地大部分形成于 MIS 5a、5c、5e（末次间冰期）和 7a。阶地在 Hikurangi 边缘前弧内保存得最好，在那里它们向西高度降低，表明长波，向西构造倾斜。阶地被一些活跃的地壳断层局部抵消，最显着的是怀拉拉帕断层和奥哈里乌断层。向西构造倾斜。阶地被一些活跃的地壳断层局部抵消，最显着的是怀拉拉帕断层和奥哈里乌断层。向西构造倾斜。阶地被一些活跃的地壳断层局部抵消，最显着的是怀拉拉帕断层和奥哈里乌断层。