Abstract This paper concerns the sedimentary successions deposited in the Mandawa Basin after the separation of East and West Gondwana during the subsequent southwards drift of Madagascar in the Late Jurassic to Early Cretaceous times. The aim of this study was to provide more specific details on the Late Jurassic and Early Cretaceous sedimentation and to report mineralogical and petrographical characteristics on the less well documented successions, namely the Kipatimu, Mitole and Nalwehe formations, in the central and northern parts of the Mandawa Basin. The Late Jurassic and Early Cretaceous depositional environments are reviewed, based on the sedimentological, mineralogical and petrographical results presented here, supplemented by previously published work. The Late Jurassic to Early Cretaceous depositional setting mainly reflects a shallow, tidally influenced, mixed carbonate-silisiclastic coastal ramp. The succession displays cyclical sedimentation best described as a series of transgressive-regressive sequences with limestones overlain by siliciclastics. During transgressions microbial activity was high and sedimentation rates low, resulting in micro-oncoid deposition in the late Kimmeridgian – early Tithonian (Mitole Limestone Member), and oncoids and stromatolites in the Early Cretaceous (Nalwehe Limestone Member). During the regressive phases siliciclastic marginal marine sediments were deposited over the limestones. The regressive sandstones are mainly unfossiliferous and display evidence of being deposited in a tide-dominated, marginal marine environment.

中文翻译：

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坦桑尼亚沿海曼达瓦盆地晚侏罗世和早白垩世沉积。

摘要 本文研究了晚侏罗世至早白垩世马达加斯加随后向南漂移期间东西冈瓦纳分离后沉积在曼达瓦盆地的沉积层序。本研究的目的是提供关于晚侏罗世和早白垩世沉积的更具体的细节，并报告记录较少的层序的矿物学和岩相特征，即在中部和北部的 Kipatimu、Mitole 和 Nalwehe 地层。曼达瓦盆地。根据此处介绍的沉积学、矿物学和岩相学结果，并辅以先前发表的工作，对晚侏罗世和早白垩世沉积环境进行了审查。晚侏罗世至早白垩世沉积环境主要反映了浅、受潮汐影响的混合碳酸盐硅质碎屑海岸斜坡。序列显示出周期性沉积，最好将其描述为一系列海侵-海退层序，其中石灰岩被硅质碎屑岩覆盖。海侵期间微生物活动高，沉积速率低，导致晚金里吉世-提通阶早期（米托勒灰岩段）和早白垩世（纳尔维赫灰岩段）的巨粒瘤和叠层石沉积。在回归阶段，硅质碎屑边缘海洋沉积物沉积在石灰岩上。退化砂岩主要是无化石的，并显示出沉积在潮汐主导的边缘海洋环境中的证据。序列显示出周期性沉积，最好将其描述为一系列海侵-海退层序，其中石灰岩被硅质碎屑岩覆盖。海侵期间微生物活动高，沉积速率低，导致晚金里吉世-提通阶早期（米托勒灰岩段）和早白垩世（纳尔维赫灰岩段）的巨粒瘤和叠层石沉积。在回归阶段，硅质碎屑边缘海洋沉积物沉积在石灰岩上。海退砂岩主要是无化石的，并显示出沉积在潮汐主导的边缘海洋环境中的证据。序列显示出周期性沉积，最好将其描述为一系列海侵-海退层序，其中石灰岩被硅质碎屑岩覆盖。海侵期间微生物活动高，沉积速率低，导致晚金里吉世-提通阶早期（米托勒灰岩段）和早白垩世（纳尔维赫石灰岩段）的巨粒状沉积物和叠层石沉积。在回归阶段，硅质碎屑边缘海洋沉积物沉积在石灰岩上。退化砂岩主要是无化石的，并显示出沉积在潮汐主导的边缘海洋环境中的证据。导致晚 Kimmeridgian – 早 Tithonian (Mitole Limestone Member) 和早白垩世 (Nalwehe Limestone Member) 的 Oncoid 和叠层石沉积。在回归阶段，硅质碎屑边缘海洋沉积物沉积在石灰岩上。退化砂岩主要是无化石的，并显示出沉积在潮汐主导的边缘海洋环境中的证据。导致晚 Kimmeridgian – 早 Tithonian (Mitole Limestone Member) 和早白垩世 (Nalwehe Limestone Member) 的 Oncoid 和叠层石沉积。在回归阶段，硅质碎屑边缘海洋沉积物沉积在石灰岩上。退化砂岩主要是无化石的，并显示出沉积在潮汐主导的边缘海洋环境中的证据。