Olisthostromes and other delapsional deposits, and their occurrence in the region of Moratalla (Prov. Of Murcia, Spain)

In the first part of this publication an attempt is made to bring some order in the terminological chaos existing in the field of delapsion, which is the independent gravitating of rock material along sloping surfaces. The term olisthon is introduced for everything that has been delapsed. For the purpose of a rational and comprehensive classification of geological phenomena delapsion is introduced as a separate class between tectonization and sedimentation. Special emphasis is laid upon the concepts of olisthostrome and olistholith, which are redefined. The principles of the mechanics involved in delapsional processes are discussed. In the second part emphasis is laid upon the description of the olisthostromes, olistholiths, reversely graded mud flow and muddy gravel avalanche deposits that invaded the Moratalla basin during the Miocene. Attention is also given to the olisthostrome occurring in the Lower Eocene, the slump packets and slip blocks in the Miocene, and to the extensive slip sheets of Cretaceous rocks that closed the depositional phase of the basin. The regional stratigraphy and tectonic structure are briefly discussed. The interpretation of the structures - the greater part of the Triassic rocks of the Subbetic zone is thought to be in autochthonous to parautochthonous position - differs from the current interpretation that the Triassic rocks form the basal part of the Subbetic nappe that would have thrust over some twenty kilometres.