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首页> 外文期刊>Sedimentology: Journal of the International Association of Sedimentologists >Formation of mud clast breccias and the process of sedimentary autobrecciation in the hominin-bearing (Homo naledi) Rising Star Cave system, South Africa
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Formation of mud clast breccias and the process of sedimentary autobrecciation in the hominin-bearing (Homo naledi) Rising Star Cave system, South Africa

机译：泥炭砂砾中的形成和南非崛起星洞穴系统的泥浆Clast Breccias及沉积自胶层的过程

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摘要

Unconsolidated mud clast breccia facies in the hominin-bearing (Homo naledi) Rising Star Cave, Cradle of Humankind, South Africa, are interpreted to have formed through a process termed sedimentary autobrecciation in this study. This process, by which most of the angular mud clast breccia deposits are thought to have formed autochthonously to para-autochthonously via a combination of erosion, desiccation, diagenesis and microbial alteration of laminated mud deposits, is thought to have taken place under relatively dry (i.e. non-flooded) conditions inside the cave. Subsequently, gravitational slumping and collapse was the dominant mechanism that produced the mud clast breccia deposits, which commonly accumulate into debris aprons. The mud clast breccia is typically associated with (micro) mammal fossils and is a common facies throughout the cave system, occurring in lithified and unlithified form. This facies has not been described from other cave localities in the Cradle of Humankind. Additionally, sedimentary autobrecciation took place during the deposition of some of the fossils within the Rising Star Cave, including the abundant Homo naledi skeletal remains found in the Dinaledi Subsystem. Reworking of the mud clast breccia deposits occurs in some chambers as they slump towards floor drains, resulting in the repositioning of fossils embedded in the breccias as evidenced by cross-cutting manganese staining lines on some Homo naledi fossil remains. The formation of the unlithified mud clast breccia deposits is a slow process, with first order formation rates estimated to be ca 8 x 10(-4) mm year(-1). The slow formation of the unlithified mud clast breccia facies sediments and lack of laminated mud facies within these deposits, indicates that conditions in the Dinaledi Chamber were probably stable and dry for at least the last ca 300 ka, meaning that this study excludes Homo naledi being actively transported by fluvial mechanisms during the time their remains entered the cave.
机译：在南非人类腰部升起的星洞（Homo Naledi）rising star洞穴中的未扑过泥浆Clastccia面部被解释为通过该研究中所谓的沉积自发性的过程形成。该方法，通过该方法，其中大多数角泥浆Clasccia沉积物被认为通过侵蚀，干燥，成岩作用和层压泥浆沉积物的组合和层压泥浆沉积物的组合而自同加密，认为已经在相对干燥（即洞穴内的未淹没）条件。随后，引力坍塌和塌陷是产生泥浆Clast Breccia沉积物的主要机制，其通常积聚成碎片围裙。泥浆Clast Breccia通常与（微）哺乳动物化石有关，并且是整个洞穴系统中的共同面，以锂化和不合格的形式发生。这张相尚未从人类摇篮中的其他洞穴中描述。此外，在升起的星洞内的一些化石沉积期间，在升起的星座内的一些化石中进行了沉积自发性，包括Dinaledi子系统中发现的丰富的Homo Naledi骨骼。在一些腔室朝向地板排水管下，泥浆Clast Breccia沉积物发生重新加工，导致嵌入在Breccias中的化石重新定位，这是由一些Homo Naledi Fossil上的交叉切割锰染色线所证明的。形成不含泥浆Clast Breccia沉积物是一种缓慢的过程，第一阶形成速率估计为Ca 8 x 10（-4）mm年（-1）。非目的泥浆CLAST Breccia面部沉积物的缓慢形成和这些沉积物内缺乏层压泥浆相表明，二核室中的条件可能稳定并至少干燥最后的CA 300 Ka，这意味着本研究不包括Homo Naledi在遗骸进入洞穴时积极通过河流机制运输。

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