Accumulations of cephalopods in the Late Ordovician (Katian [Ka4]) Troutbeck Siltstone Member of the Ash Gill Mudstone Formation at Skelghyll Beck in the Lake District and in the Keisley Limestone Formation of the Cross Fell Inlier contribute toward an understanding of their respective depositional environments as well as the palaeogeography of the southeastern margins of the Lakesman Terrane. The accumulation present in the Troutbeck Siltstone Member is interpreted as having been deposited in a shallow, near-shore lagoon that supported stromatolite growth. The shore lay to the north of this site. Geopetals infilling cephalopods forming concentrations in the Keisley Limestone Formation indicate that the conchs came to rest on angles of 30–40° to horizontal. The lithologies of the matrix suggest that they were deposited in cavities or fissures from which fine-grained carbonate was either excluded or winnowed away. Both observations accord with hypotheses that the Keisley Limestone Formation represents the remnants of a carbonate mud mound, and facilitate comparison with the contemporaneous Boda mounds of Siljan, Sweden. Comparison with local late Katian – Hirnantian successions indicate that the Keisley mound would have formed a prominent feature on the sea floor, becoming largely buried by argillaceous sediments during the Hirnantian.

晚奥陶世 (Katian [Ka4]) Troutbeck 粉砂岩中的头足类动物在湖区 Skelghyll Beck 的 Ash Gill 泥岩组和 Cross Fell Inlier 的 Keisley 石灰岩组中的堆积有助于了解它们各自的沉积环境，如以及 Lakesman Terrane 东南边缘的古地理。存在于 Troutbeck 粉砂岩段的堆积物被解释为沉积在支持叠层石生长的浅的近岸泻湖中。海岸位于该地点的北部。在 Keisley 石灰岩组中填充头足类动物的地质花瓣表明海螺与水平面的角度为 30-40°。基质的岩性表明它们沉积在孔洞或裂缝中，细粒碳酸盐要么被排除在外，要么被风吹走。这两个观察结果都符合凯斯利石灰岩组代表碳酸盐泥丘残余物的假设，并有助于与瑞典 Siljan 的同期博达丘进行比较。与当地晚期 Katian-Hirnantian 序列的比较表明，Keisley 土丘将在海底形成一个突出的特征，在 Hirnantian 期间大部分被泥质沉积物掩埋。瑞典。与当地晚期 Katian-Hirnantian 序列的比较表明，Keisley 土丘将在海底形成一个突出的特征，在 Hirnantian 期间大部分被泥质沉积物掩埋。瑞典。与当地晚期 Katian-Hirnantian 序列的比较表明，Keisley 土丘将在海底形成一个突出的特征，在 Hirnantian 期间大部分被泥质沉积物掩埋。