Morphotectonic control on Quaternary sedimentation and landscape evolution, Pachham Island, Kachchh, Western India
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ORIGINAL PAPER
Morphotectonic control on Quaternary sedimentation and landscape evolution, Pachham Island, Kachchh, Western India V. Chowksey 1 & D. M. Maurya 1 & N. Khonde 1 & L. S. Chamyal 1
Received: 5 November 2015 / Accepted: 1 August 2016 # Saudi Society for Geosciences 2016
Abstract Pachham Island is the westernmost island in a chain of four rocky islands within the Great Rann of Kachchh that are bounded in the north by the Island Belt Fault (IBF). The island is characterized by two parallel and structurally controlled Kaladungar hill range and Goradungar hill range separated by a synclinal central valley. The central valley has acted as a sink for the Quaternary sediments. The island is transversely traversed by a N-S trending basement high termed as Median high that shows pronounced geomorphic and drainage anomaly. The Quaternary sediments comprise coarse-grained colluvio-fluvial deposits, miliolite, and sandy alluvium. The coarse-grained Quaternary deposits were primarily derived from the colluvium generated due to the uplift of the Kaladungar hill range and Goradungar hill range along the IBF and Goradunagar Fault, respectively. The colluvial debris were subsequently reworked, transported down slope and deposited in the central valley. The presence of the deeply incised valleys in Quaternary sediments, two levels of terrace surfaces over the Median high, and the raised Rann floor surrounding the island suggest a dominant role of neotectonics in the landscape evolution and Quaternary sedimentation.
Keywords Morphotectonic . Colluvio-fluvial deposits . Quaternary . Pachham Island . Island belt fault (IBF) . Goradungar fault . Kachchh . Western India
* D. M. Maurya [email protected]
1
Department of Geology, The M. S. University of Baroda, Vadodara -390 002, India
Introduction The Kachchh basin is a seismically active paleo-rift graben at the western continental margin of India. The formation of the rift basin took place as a consequence of the separation of the Indian plate with the Gondwanaland which resulted in the deposition of a thick sequence of marine sediments until late Cretaceous (Biswas 1987). Inversion of the basin at the end of the Cretaceous led to the formation of several uplifts bounded by an E-W trending intrabasinal faults (Biswas and Khattri 2002). The major fault-bounded uplifts are the Island Belt Uplift, Kachchh Mainland Uplift, and the Wagad uplift. These are controlled by the Island Belt Fault (IBF), Kachchh Mainland Fault (KMF), and the South Wagad Fault (SWF) respectively (Fig. 1). The intervening lows formed the sites for the deposition of Tertiary and Quaternary sediments including the vast Rann of Kachchh—a flat terrain formed by the uplift of the floor of the Holocene sea (Glennie and Evans 1976; Merh 2005). The basin is also characterized by a N-S trending subsurface basement high called the Median high in the central part of the basin that has been shown to be active during the syn-rift and the post-rift phases of the basin evolution (Biswas 1987). Quaternary sediment
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