The upper estuarine series of the East Midlands.

The purpose of the present study, of which some of the results are here presented, was to investigate and describe the Upper Estuarine Series and its sediments. It has been shown that the Series is best described as a bipartite formation rather than tripartite, as has been the case until now. The two divisions have been named, the Lower Freshwater Sequence, and the Rhythmic Sequence. Both names describe the general character of the divisions involved. The former name retains its original connotation. it can be demonstrated that the upper two thirds of the Series which have been celled until now, the Upper Estuarine Limestone, and the beds above the Upper Estuarine Limestone, are essentially rhythmic in character. Both limestones and clays have a repetitive sedimentary form, which is generally an upward change from a laminated texture to a homogeneous texture. Limestones may be developed in any of the rhythms, but are more common in the higher ones. The position within a rhythm determines the limestones characterestics. Those limestones which are developed at the base tend, like the crays, to be laminated, when they occur at the top of a rhythm they tend to be bioturbated and homogeneous in texture. The lowest rhythm which has been traced wherever the Upper Estuarine Series overlies the Lincolnshire Limestone is invariably marked by the occurrence or Lingula kestevenensis within the lower two feet. Lingula has never been found above this horizon. Upwards there is evidence of a passage sequence of sediments into the Great Oolite Limestone. The occurrence of a lacustrine-deltaic complex in the Lower Freshwater Sequence can be demonstrated, and shows "estuarine" to be a misnomer in the strictest sense. The ostracod fauna is described and there is evidence that, although marine conditions were dominant, it is likely that at times freshwater and brackish conditions influenced the Rhythmic Sequence. A study of the clay miner logy has shown that changes occur upwards through the two rhythms investigated, and it is considered that leaching during upper Estuarine time was the cause. An occurrence of echinoderms in the limestones at Blisworth has been studied and their preservation has been found to reflect the mode of death and burial, and has also shed some light on the conditions of deposition in the rimes tones. The thick, well developed, limestones of the Upper Estuarine Series have been studied and it has been found that lateral sedimentation played an important role in their deposition. Directional indicators are scarce in the upper Estuarine Series, but when they are present they give every indication of a southerly derivation for the sediment, both for the Lower Freshwater Sequence and the Rhythmic Sequence