Palaeoproterozoic seismites (fine-grained facies of the Chaibasa Formation, east India) and their soft-sediment deformation structures
Published:January 01, 2009
R. Mazumder, J. P. Rodríguez-López, M. Arima, A. J. Van Loon, 2009. "Palaeoproterozoic seismites (fine-grained facies of the Chaibasa Formation, east India) and their soft-sediment deformation structures", Palaeoproterozoic Supercontinents and Global Evolution, S. M. Reddy, R. Mazumder, D. A. D. Evans, A. S. Collins
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Metamorphosed shales, heterolithic deposits and sandstones build up the Palaeoproterozoic Chaibasa Formation in east India. The shales (referred here to as the fine-grained facies) comprising mudstone (clay and silt size) with some minor amounts of very fine to fine sandstone were deposited below storm wave base in a deep marine basin that simultaneously underwent tectonic activity. This fine-grained facies contains strongly deformed layers, intercalated between undeformed layers. Sedimentological analysis of the deformations indicates that they formed while still in an unconsolidated or slightly consolidated state, partly during and after sedimentation, but before being covered by younger sediments. The types of deformation structures indicate an earthquake-induced origin. Thus, they should be considered as seismites. The soft-sediment deformation structures in the seismites show a wide variety of shapes and other characteristics that appear to depend on their relative position to the epicentre of the earthquake.
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Palaeoproterozoic Supercontinents and Global Evolution
The Palaeoproterozoic era (2500–1600 Ma) was a critical period of Earth history, with dynamic evolution from the deep planetary interior to its surface environment. Several lines of geological evidence suggest the existence of at least one pre-Rodinia supercontinent, named Nuna or Columbia, which formed near the end of Palaeoproterozoic time. Prior to this assembly, there may have been an older supercontinent (Kenorland) or perhaps only independently drifting supercratons. The tectonic records of amalgamation and dispersal of these ancient landmasses provide a framework that links processes of the deep Earth with those of its fluid envelope. The sixteen papers in this volume present reviews and new analytical data that span the geological record of Palaeoproterozoic Earth and provide a current picture of Palaeoproterozoic research. The volume provides a useful reference book for students and professional geoscientists interested in this important period of global evolution.