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PLASTIC FLOW AND CONTRAFLOW IN SUPERPOSED ZECHSTEIN SALT SEQUENCES
Author(s) -
Jenyon M. K.
Publication year - 1989
Publication title -
journal of petroleum geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.725
H-Index - 42
eISSN - 1747-5457
pISSN - 0141-6421
DOI - 10.1111/j.1747-5457.1989.tb00245.x
Subject(s) - geology , salt (chemistry) , anhydrite , petrology , salt tectonics , borehole , flow (mathematics) , evaporite , deformation (meteorology) , reflection (computer programming) , structural basin , seismology , mineralogy , geotechnical engineering , diapir , geomorphology , paleontology , geometry , oceanography , chemistry , mathematics , gypsum , computer science , programming language
A competent band within a salt‐rock sequence can be a useful indicator of the form taken by any plastic deformation movement that occurs in the salt. The acoustic impedance contrasts provided by such a band often result in strong seismic reflection events that exhibit the effects of all stages of deformtion accompanying salt movement, from gentle undulations through complete disintegration the competent unit. Examples are shown in seismic data from the North Sea Zechstein of deformation of the Plattendolomit band that separates the underlying Z2 ‐ cycle salt from the salt of the overlying Z3 cycle. Cases are discussed in which the evidence suggests contraflow in the two salts, where the Z2 salt has flowed bi‐directionally away from the axial trough of a salt‐withdrawal basin. This has led to flow of the overlying Z3 salt bi‐directionally towards the same axis. The observations tell us something about the rheological behaviour of superposed salts, and about the deformational behaviour of competent carbonate/anhydrite bands within a salt sequence. They also highlight potential problems of well correlation in the absence of good seismic data, or due to misunderstanding of salt‐flow phenomena.