The Lower Palaeozoic Geosyncline

Abstract

The principal interest of the Lower Palaeozoic era in the British area lies in the development of a geosyncline which later became transformed, by major folding movements, into a folded-mountain chain. A geosyncline (Fig. 5) can be defined as an elongated downwarping of the crust of the earth, forming a deep trough in which a great thickness of sediments accumulates. This definition needs to be somewhat enlarged. First the downwarp is occupied by the sea and the environment of sedimentation is normally marine. Secondly, sedimentation may, or may not, keep pace with the downwarping, the sediments being therefore of shallow-water type in the former case but of deep-water type in the second. Thirdly, an essential part of the definition is that the geosynclinal sediments are later compressed and folded by the movement together of the sides of the downwarp, and so come to form fold-mountains.