Peritidal stromatolites as indicators of stepping-stone freshwater resources on the Palaeo-Agulhas Plain landscape
Peritidal stromatolites as indicators of stepping-stone freshwater resources on the Palaeo-Agulhas Plain landscape
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潮间叠层石作为古厄加勒斯平原景观垫脚石淡水资源的指标
DOI：
10.1016/j.quascirev.2019.03.026
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发表时间：
2020
影响因子：
4
通讯作者：
R. Perissinotto
中科院分区：
文献类型：
--
作者：
G. Rishworth;H. Cawthra;Carla Dodd;R. Perissinotto
淡水的天然来源是限制依赖定期水合作用的陆地物种分布的一个特征，特别是在沿海环境中。早期的现代人类同样会受到水供应的限制，可能会聚集或定居在永久性水体附近，例如大河的河口范围之外。然而，沿着现代南部非洲的南海岸，例如，淡水与河流之间的距离可能超过方便的每日步行限制。在缺乏替代供水或蓄水手段的情况下，这些距离将使人类无法在河流边界以外定居。最近发现的生活围潮层形成沿着南非南部海岸线建议一个潜在的替代水源。这些独特的生态系统只有在富含碳酸钙的地下水与沿海边缘沿着定期的海洋入侵相遇的地方才能形成。碳酸钙被蓝藻沉淀，沉积物被硅藻捕获，主要形成分层沉积物，保存在化石记录中。对这些叠层石的形成和生长至关重要的是新鲜的、不间断的地下水供应。在它们的生长过程中，潮缘叠层石通过在新海岸地质露头的向海边缘形成边石坝和拦河坝池来积累和保留这些淡水。对于早期人类来说，认识到河流以外的永久性水源的存在是具有挑战性的;然而，这些叠层提供了替代水资源的明确标志。在这里，我们回顾了现代流行的潮周叠层石在这一地区，其中约540已知沿着200公里的南非南部海岸线只有11个河口。这与功能有关（参见边缘石坝和拦河坝池），类似于在邻近的古阿古拉斯平原景观的潮缘叠层石，使用多波束回声测深仪和侧扫声纳数据，并作为早期现代人类可能的水资源的背景。
Natural sources of freshwater are a limiting feature to the distribution of terrestrial species that rely on regular hydration, especially in coastal environments. Early modern humans would similarly be restricted by water supply and likely would have congregated or settled in close proximity to permanent water bodies such as beyond the estuarine extent of large rivers. However, along the modern south coast of southern Africa, for example, distances between freshwater from rivers can exceed what would be convenient daily walking limits. In the absence of alternative water supply, or a means of water storage, these distances would preclude human settlement beyond river borders. Recent discovery of living peritidal stromatolites forming along the southern South African coastline suggests a potential alternative water source. These unique ecosystems form only at locations where groundwater rich in calcium carbonate meets periodic marine intrusion along the coastal margin. Calcium carbonate is precipitated by cyanobacteria and sediment is trapped by diatoms, primarily, to form layered deposits that preserve into the fossil record. Critical to the formation and growth of these stromatolites is a fresh, uninterrupted supply of groundwater. During their growth, the peritidal stromatolites accumulate and retain this freshwater through the formation of rimstone dams and barrage pools at the seaward margin of neocoastal geological outcrops. Recognising the presence of permanent water sources other than rivers for early humans is challenging; however, these stromatolites provide a clear signature of an alternative water resource. Here we review the modern prevalence of peritidal stromatolites in this region, of which approximately 540 are known along a 200 km stretch of South Africa's southern coastline featuring only 11 estuaries. This is linked to features (cf. rimstone dams and barrage pools) resembling peritidal stromatolites in the adjacent Palaeo-Agulhas Plain landscape using multibeam echosounder and side-scan sonar data and contextualised as a possible water resource for early modern humans.