ABSTRACT

Early Miocene limestones from the Wairarapa region of New Zealand were deposited on thrust-bounded margins of trench-slope basins, and consist of two superposed stratal units, namely units A and B, interpreted as forced regressive and forced transgressive foralgal and rhodolith-bearing deposits, respectively. Unit A is floored by a regressive surface of marine erosion cut into shelfal to bathyal siliciclastic successions, and is overlain across a transgressive surface of erosion by Unit B. A drowning surface abruptly places the latter deposits in contact with deeper hemipelagites and turbidites. The succession is explainable within a tectono-eustatic based framework as follows: (1) Structurally controlled rapid relative sea-level fall, (i.e. sea-bed rise), from upper bathyal to shelfal depths promoted development of regressive (‘lowstand’) mixed carbonate–siliciclastic deposits. Continuation of seabed rise resulted in deposition of pure carbonate sediments, which are represented by channel-fill rhodolithic rudstones; (2) early stage of relative sea-level rise (i.e. seabed drowning) caused emplacement of transgressive glauconitic limestones, consisting of either foralgal deposits, or incised rhodolithic limestones; (3) continued relative sea-level rise terminated carbonate production. The present study documents carbonate production and termination in a tectonically active and confined intra-slope setting, reflected in the development and distribution of unusual forced regressive, and transgressive rhodolithic-heterozoan carbonates.

摘要

来自新西兰怀拉拉帕地区的早中新世石灰岩沉积在沟槽斜坡盆地的逆冲边界边缘，由两个叠置的地层单元组成，即单元 A 和 B，被解释为强制海退和强制海进的藻藻和含红石的沉积物， 分别。单元 A 的底部是海洋侵蚀的海退表面，切割成陆架到深海硅质碎屑层序，并覆盖在单元 B 的侵蚀海侵表面上。淹没表面突然使后者沉积物与更深的半海藻和浊积岩接触。在基于构造-海平面的框架内，该序列可以解释如下：（1）结构控制的快速相对海平面下降（即海床上升），从上深海到陆架深度促进了海退（“低位”）混合碳酸盐-硅质碎屑矿床的发展。海床的继续上升导致纯碳酸盐沉积物的沉积，以河道充填红石质砾石为代表；(2) 相对海平面上升的早期阶段（即海底淹没）造成海侵海绿石灰岩的就位，由藻类沉积物或下切红石灰岩组成；(3) 持续的相对海平面上升终止了碳酸盐的生产。本研究记录了在构造活动和受限的斜坡内环境中碳酸盐的产生和终止，反映在异常的强迫海退和海侵红石-杂虫碳酸盐的发展和分布中。海床的继续上升导致纯碳酸盐沉积物的沉积，以河道充填红石质砾石为代表；(2) 相对海平面上升的早期阶段（即海底淹没）造成海侵海绿石灰岩的就位，由藻类沉积物或下切红石灰岩组成；(3) 持续的相对海平面上升终止了碳酸盐的生产。本研究记录了在构造活动和受限的斜坡内环境中碳酸盐的产生和终止，反映在异常的强迫海退和海侵红石-杂虫碳酸盐的发展和分布中。海床的继续上升导致纯碳酸盐沉积物的沉积，以河道充填红石质砾石为代表；(2) 相对海平面上升的早期阶段（即海底淹没）造成海侵海绿石灰岩的就位，由藻类沉积物或下切红石灰岩组成；(3) 持续的相对海平面上升终止了碳酸盐的生产。本研究记录了在构造活动和受限的斜坡内环境中碳酸盐的产生和终止，反映在异常的强迫海退和海侵红石-杂虫碳酸盐的发展和分布中。海底溺水）导致海侵海绿石石灰岩的就位，由藻类沉积物或切开的红石石灰岩组成；(3) 持续的相对海平面上升终止了碳酸盐的生产。本研究记录了在构造活动和受限的斜坡内环境中碳酸盐的产生和终止，反映在异常的强迫海退和海侵红石-杂虫碳酸盐的发展和分布中。海底溺水）导致海侵海绿石石灰岩的就位，由藻类沉积物或切开的红石石灰岩组成；(3) 持续的相对海平面上升终止了碳酸盐的生产。本研究记录了在构造活动和受限的斜坡内环境中碳酸盐的产生和终止，反映在异常的强迫海退和海侵红石-杂虫碳酸盐的发展和分布中。