ABSTRACT

The Hemse Group is one of the least understood stratigraphic units of the Silurian sequence of Gotland, Sweden. New results from airborne transient electromagnetic (ATEM) measurements in combination with previously published data from field studies and geophysical investigations shed new light on carbonate platform development during the early- to mid-Ludlow Hemse Group. ATEM reveals a transgressive phase that began near the Wenlock-Ludlow boundary, which resulted in deposition of marls and corresponds roughly to the Hemse limestone units a-c and the Hemse Marl NW. In this phase little or no reef development occurs. The end of the transgressive phase coincides with the weak Linde Event. The following highstand favoured extensive reef growth forming a reef barrier system of both fringing reefs and more rampiform settings with stromatoporoid biostromes and occasional biohermal buildups. The Kuppen-Snabben Unconformity Complex marks an erosional (karstic) sequence boundary and rocky shoreline and the transition from a rampiform setting with reef biostromes towards a more rimmed setting with patch reefs.

摘要

Hemse组是瑞典哥得兰岛志留系层序中最鲜为人知的地层单位之一。机载瞬变电磁（ATEM）测量的新结果与先前发表的现场研究和地球物理研究数据相结合，为Ludlow Hemse组早期至中期的碳酸盐岩平台开发提供了新的思路。ATEM揭示了一个海相阶段，该相开始于温洛克-卢德洛边界附近，其导致了泥灰沉积，大致对应于Hemse石灰石单元ac和Hemse Marl NW。在此阶段，很少或根本没有珊瑚礁发育。海侵阶段的结束与薄弱的林德事件相吻合。接下来的高潮期有利于广泛的礁石生长，形成边缘礁的礁石屏障系统，以及层状多孔生物层和偶尔的生物体堆积，形成更多的斜坡状环境。Kuppen-Snabben不整合面体标志着侵蚀性（岩溶性）层序边界和多岩石的海岸线，以及从具有礁石生物界的斜坡状环境向具有斑驳礁石的更边缘环境的过渡。