Lacustrine sedimentation in the diapir-controlled Miocene Bicorb Basin, eastern Spain

The Miocene Bicorb Basin is a small elongated basin developed by normal faulting of a thick Jurassic-Cretaceous carbonate succession and subsequent diapirism of Upper Triassic mudstones and evaporites. The basin fill comprises a sequence over 650 m thick formed by two units. The lower, alluvial unit consists of a complex alternation of conglomerates, sandstones, mudstones, and minor lacustrine limestones. The upper unit comprises marginal alluvial and lacustrine deposits in which seven lacustrine facies associations have been distinguished, The inner lacustrine deposits comprise mudstones and carbonates with minor evaporitic deposits. At the northeast and southwest basin edges, alluvial inputs led to the development of delta and fan-delta environments where sandstone and conglomerate deposits dominate, The latter stages of the lake evolution are represented by an expansive thick limestone sequence which close to the NW fault-bounded margin pass laterally to breccias, The hierarchical arrangement of the upper unit shows five different orders of sequences. The first-order sequence defines a major vertical trend of lake expansion whereas three second-order sequences are linked to major flooding-expansion episodes. All these sequences are related to the tectonic evolution of the diapir. Metre-scale, third- and fourth-order sequences and fifth-order sequences, which consist of finely laminated rhythmite deposits probably record climatically forced processes. The diapir-graben system evolution and the climatic variations have exerted major controls on the sequential arrangement and evolution of the lacustrine system. Both factors have also strongly influenced the changes in the gastropod assemblages. (C) 1998 Elsevier Science B.V. All rights reserved.