Pliocene glaciations, post-glacial Tyrrell Sea deposition, peatland formation, and continuous isostatic uplift have created a unique environment for karst development on the Paleozoic carbonate rocks within the James Bay Lowland of Canada. Four types of sinkhole and two karst hydrogeological systems have been recognized in the study area. The hydrogeologically active karst system consists of solution sinkholes, solutionally enlarged fractures, and collapse sinkholes that have developed after the area emerged from the Tyrrell Sea approximately 4400 years ago. The active karst system encompasses the exposed reefal limestone of the Silurian Attawapiskat Formation along the Attawapiskat River and Nayshkootayaow River and isolated bioherms that protrude above the surrounding flat but poorly drained peatland between the two major rivers. The second karst system is in the form of paleokarst formed in the underlying limestone but buried beneath the peat and marine sediments. Although these buried sinkholes were only visible at excavation sites where these features were exposed, it is likely that they underlie most of the study area. Another form of paleokarst is the Bedrock Trench that cut through most of the Paleozoic formation to a depth of approximately 200 m. The bedrock trench encompassed an area of more than 3 km2, was filled with unconsolidated materials, and did not have strong hydraulic connections to the active karst system. Formation mechanism of this bedrock trench is inconclusive but may result from polygenetic processes including glacial scouring and bedrock dissolution. Recognition of these two karst systems helps understand potential hydrogeological changes in response to continuous isostatic uplift and dewatering activities in this region.

中文翻译：

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加拿大安大略省北部泥炭地复合体中的天坑及其对岩溶水文地质的影响

上新世冰川作用、冰后泰瑞尔海沉积、泥炭地形成和持续的均衡隆升为加拿大詹姆斯湾低地古生代碳酸盐岩的岩溶发育创造了独特的环境。研究区已识别出四种落水洞和两种岩溶水文地质系统。水文地质活动岩溶系统由溶蚀坑、溶蚀扩大的裂缝和坍塌落坑组成，这些溶洞是该地区大约 4400 年前从泰瑞尔海出现后形成的。活跃的喀斯特系统包括沿 Attawapiskat 河和 Nayshkootayaow 河的志留系 Attawapiskat 组的裸露礁灰岩和孤立的生物礁，这些生物礁突出在两条主要河流之间的周围平坦但排水不良的泥炭地之上。第二个岩溶系统是在下面的石灰岩中形成的古岩溶形式，但埋在泥炭和海洋沉积物之下。尽管这些埋藏的天坑仅在暴露这些特征的挖掘地点可见，但它们很可能是大部分研究区域的基础。另一种古岩溶形式是基岩海沟，它穿过大部分古生代地层，深度约为 200 m。基岩沟的面积超过 3 平方公里，充满松散物质，与活跃的岩溶系统没有强大的水力连接。该基岩海沟的形成机制尚无定论，但可能是由冰川冲刷和基岩溶解等多基因过程造成的。