ABSTRACT

Glacio-eustatic cycles lead to changes in sedimentation on all types of continental margins. There is, however, a paucity of sedimentation rate data over eustatic sea-level cycles in active subduction zones. During International Ocean Discovery Program Expedition 375, coring of the upper ∼110 m of the northern Hikurangi Trough Site U1520 recovered a turbidite-dominated succession deposited during the last ∼45 kyrs (Marine Isotope Stages (MIS) 1–3). We present an age model integrating radiocarbon dates, tephrochronology, and δ¹⁸O stratigraphy, to evaluate the bed recurrence interval (RI) and sediment accumulation rate (SAR). Our analyses indicate mean bed RI varies from ∼322 yrs in MIS1, ∼49 yrs in MIS2, and ∼231 yrs in MIS3. Large (6-fold) and abrupt variations in SAR are recorded across MIS transitions, with rates of up to ∼10 m/kyr occurring during the Last Glacial Maximum (LGM), and <1 m/kyr during MIS1 and 3. The pronounced variability in SAR, with extremely high rates during the LGM, even for a subduction zone, are the result of changes in regional sediment supply associated with climate-driven changes in terrestrial catchment erosion, and critical thresholds of eustatic sea-level change altering the degree of sediment bypassing the continental shelf and slope via submarine canyon systems.

摘要

冰川-海平面旋回导致所有类型大陆边缘的沉积发生变化。然而，在活跃的俯冲带中，海平面海平面旋回的沉降速率数据很少。在国际海洋发现计划 375 远征期间，Hikurangi Trough Site U1520 北部约 110 m 的取心恢复了最后约 45 kyrs（海洋同位素阶段 (MIS) 1-3）沉积的浊积岩为主的层序。我们提出了一个整合了放射性碳年代、年代学和 δ18 的年龄^模型O 地层学，用于评估河床复发间隔 (RI) 和泥沙堆积率 (SAR)。我们的分析表明，平均床 RI 在 MIS1 中约为 322 年，在 MIS2 中约为 49 年，在 MIS3 中约为 231 年。在 MIS 过渡期间记录到 SAR 的大（6 倍）和突然变化，在末次盛冰期 (LGM) 期间发生的速率高达 ∼10 m/kyr，在 MIS1 和 3 期间发生 <1 m/kyr。 SAR 的变化，在 LGM 期间具有极高的速率，即使对于俯冲带也是如此，这是与气候驱动的陆地集水区侵蚀变化相关的区域沉积物供应变化的结果，以及海平面变化的临界阈值改变程度沉积物通过海底峡谷系统绕过大陆架和斜坡。