ABSTRACT

New biostratigraphically constrained chronologies have been developed to help elucidate the sedimentary and tectonic history of Quaternary sequences on the Hikurangi margin of north-eastern Zealandia. Three sites on the mid to lower slope of the accretionary prism (IODP Site 372-U1517, 375-U1519, 375-U1518) and two sites east of the deformation front (Hikurangi Trough Site 375-U1520 and Tūranganui Seamount Site 375-U1526) are dated using a detailed biostratigraphic framework based on planktic foraminiferal records from ODP Site 181-1123. The dating indicates sedimentation rates are very high and variable on the accretionary prism (0.2–9.6 m/kyr), especially during the Last Glacial Maximum (LGM) when downslope redeposition from the continental shelf and upper slope is common. Sedimentation rates at Hikurangi Trough Site 375-U1520 are also variable (0.01–3.0 m/kyr) and they increase markedly as the incoming site approached the deformation front, especially during the LGM, due to an abundance of downslope redeposition from the inner to mid shelf. The incoming Quaternary section at Tūranganui Seamount Site 375-U1526, is punctuated by hiatuses that shorten in duration as the site approached the deformation front, whilst sedimentation rates remain relatively low (0.04–0.4 m/kyr).

摘要

新的受生物地层约束的年代学已被开发出来，以帮助阐明西兰东北部 Hikurangi 边缘第四纪层序的沉积和构造历史。增生棱柱中下坡的三个地点（IODP 地点 372-U1517、375-U1519、375-U1518）和变形前沿以东的两个地点（Hikurangi Trough Site 375-U1520 和 Tūranganui Seamount Site 375-U1526）使用基于来自 ODP 站点 181-1123 的浮游有孔虫记录的详细生物地层框架来确定日期。测年表明，增生棱柱的沉积速率非常高且多变（0.2-9.6 m/kyr），特别是在末次盛冰期（LGM）期间，大陆架和上斜坡的下坡再沉积很常见。Hikurangi Trough Site 375-U1520 的沉降速率也是可变的（0.01–3.0 m/kyr），随着进入位点接近变形前沿，特别是在 LGM 期间，由于从内部到中部的大量下坡再沉积，它们显着增加架子。在 Tūranganui Seamount Site 375-U1526 进入的第四纪剖面被中断，随着该站点接近变形前沿，持续时间缩短，而沉降速率保持相对较低（0.04-0.4 m/kyr）。