Luminescence chronometry and geomorphic evidence of active fold growth along the Kachchh Mainland Fault (KMF), Kachchh, India: Seismotectonic implications

The Kachchh region of Western India is a pericratonic basin experiencing periodic high magnitude earthquakes events. In 2001 a catastrophic seismic event occurred at Bhuj measuring M_w = 7.7. The epicenters of both the 1956 and 2001 earthquakes were along the Kachchh Mainland Fault (KMF), proximal to the eastern end of the Northern Hill Range (NHR). The latter is a topographic expression of an active fault related fold on the hanging wall, and is controlled by a south dipping blind thrust.The present study deals with the eastern sector of NHR and uses optical dating to reconstruct the chronology of tectonically caused incisions. Along the backlimb of the NHR, incision ages on, channel fills and valley fill terraces progressively decrease from  12 ka to 4.3 ka. This age progression along with geomorphic evidences (decrease in topographic relief, drainage capture and drainage migration across the fold nose) suggests an active vertical and lateral fold growth along the KMF. Optical ages suggest that during the Late Holocene, the average uplift rate along the eastern NHR was 10 ± 1 mm/a. Recent GPS based estimates on crustal shortening are  12 mm/a.The KMF and the South Wagad Fault (SWF) represent the bounding faults of a transtensional basin that formed during the initial rifting. This basin is termed as the Samakhiali basin. The compressive stresses on account of structural inversion from normal to reverse phase resulted in lobate-shaped anticlines along KMF and SWF zone. These anticlines subsequently coalesced and formed linked and overlap segments. The present study suggests that eastward lateral deformation across the eastern portion of KMF has continued and has now resulted in its interaction with a left step over transfer fault called the South Wagad Master Fault (SWMF). This implies an increasing transpersional deformation of the Samakhiali basin. We therefore, suggest that the eastward NHR ridge propagation along KMF resulted in the thrust faulting on the south dipping SWMF resulting in the Bhuj 2001 event. The increasing strain on this basin may cause enhanced seismicity in the future along the eastern KMF and Wagad region.     

Facies analysis and depositional environment of the Jurassic, Jumara Dome sediments, Kachchh, western India

The study deals with the depositional environment of Jumara Dome sediments. The Jumara Dome is an important outcrop of Bathonian to Oxfordian sediments amongst the Kachchh Mainland exposures. On the basis of facies analysis three associations have been documented, namely, G-1 consisting of low energy facies comprising of cross-bedded sandstone, massive sandstone, grey shale and thin bedded sandstone, bioclastic — lithoclastic grainstone, bioclastic — lithoclastic packstone, microbioclastic packstone/wackestone, bioturbated laminated wackestone to mudstone and pelagic lime mudstone; G-II consisting of moderate energy facies comprising of laminated sandstone and grapestone or agglutinated grainstone; G-III consisting of high energy facies comprising of interbedded gypsiferous shale and sandstone/siltstone, oolitic grainstone to conglomerate and bioclastic grainstone. The facies associations reflect an ideal shallowing upward sequence representing slope, bioclast bar, lagoon and inner shelf. Presence of wide range of facies indicates that the rocks of the studied area were deposited during the fluctuating sea level, interrupted by the storms, in the shallow marine environment.     

Paleoecological significance of the trace fossils of Dhosa Oolite Member (Jumara Formation), Jhura dome,Mainland Kachchh,Western India

Dhosa Oolite Member of the Jumara Formation comprises alternating bands of oolitic limestones and shales, exposed in Jhura dome of Mainland Kachchh, Western India. This sequence is highly bioturbated and exhibits a moderate diversity and behaviourally complex assemblage of ichnospecies. The rhythmically bedded sequence shows three different levels of preservation of traces. Epichnial tiering consists of moderately bioturbated oolitic limestone exhibiting horizontal or low-angle protrusive/retrusive biogenic laminae, commonly dominated by feeding structures like Rhizocorallium jenense, R. irregulare, Zoophycos brianteus and Zoophycos isp. The endichnial structures within the oolitic limestone can be separated into two different preservational trace fossil suites. The endichnial shallow suites consist chiefly of deposit feeders like Chondrites intricatus, C. targionii, Planolites beverleyensis, Taenidium cameronensis, Thalassinoides isp., Z. brianteus, Z. cf circinnatus and Zoophycos isp. and few suspension feeder forms like Palaeophycus tubularis; while endichnial deep suites consist of Chondrites intricatus, Skolithos linearis and Zoophycos isp. Hypichnial structures consists abundant, cylindrical, branched, horizontal, large-sized three dimensional feeding burrows of Thalassinoides isp. and somewhat irregular, obtuse angle ramification burrows of Phycodes isp., which are attached to the lower surface of the casting medium. The trace fossil association indicates Cruziana ichnofacies and abundance of Zoophycus species below the fair weather wave base level is largely a preservational artifact. The preservational processes of the trace fossils indicate soft substrate and diversity and their abundance reflects the other palaeoecological parameters of the open shallow marine environments.     

Some Calloporid (Bryozoa: Cheilostomata) species from the Cenozoic sediments of western Kachchh,Gujarat

Seven species of Calloporid (family Calloporidae Norman, 1903) Bryozoa are described from the Cenozoic sediments of the western Kachchh, Gujarat, India. Among these Planicellaria walsariensis, Dionella sp., Pyriporella charopadiensis, P. vadsariensis and Wilbertopora sp. are new and the other species viz; Crassimarginatella blandfordi and Reptoporina chhasraensis are reported for the second time from these sediments. The phylogenetic analysis suggests all the species of Calloporid bryozoans are monophyletic i.e. all of these species have common ancestor.     

Active fault traces along Bhuj Fault and Katrol Hill Fault, and trenching survey at Wandhay, Kachchh, Gujarat, India

Several new active fault traces were identified along Katrol Hill Fault (KHF). A new fault (named as Bhuj Fault, BF) that extends into the Bhuj Plain was also identified. These fault traces were identified based on satellite photo interpretation and field survey. Trenches were excavated to identify the paleoseismic events, pattern of faulting and the nature of deformation. New active fault traces were recognized about 1km north of the topographic boundary between the Katrol Hill and the plain area. The fault exposure along the left bank of Khari River with 10m wide shear zone in the Mesozoic rocks and showing displacement of the overlying Quaternary deposits is indicative of continued tectonic activity along the ancient fault. The E-W trending active fault traces along the KHF in the western part changes to NE-SW or ENE-WSW near Wandhay village. Trenching survey across a low scarp near Wandhay village reveals three major fault strands F1, F2, and F3. These fault strands displaced the older terrace deposits comprising Sand, Silt and Gravel units along with overlying younger deposits from units 1 to 5 made of gravel, sand and silt. Stratigraphic relationship indicates at least three large magnitude earthquakes along KHF during Late Holocene or recent historic past.     

Geomorphic evidences of tectonic instability during the Late Quaternary Period along southern Saurashtra,western India

The coastal tract of southern Saurashtra has been studied for spectacular Miliolite Formation—its origin and depositional environment. The region had witnessed two moderate earthquakes of M_w 5.0 and 5.1 during 2007 and 2011. However, there have been limited studies which pronounce the geological and geomorphic evidences of neotectonics in southern Saurashtra. Also, there exists little to no information regarding the presence of faults from the region. The paper presents geological and geomorphic evidences of neotectonics from region between Somnath to Jafrabad, western India. A geospatial dataset was used to highlight the neotectonically active nature of the region, as well as support the claim with field evidences and drainage network anomalies. The morphometric parameters like longitudinal river profile, drainage basin asymmetry, and hypsometric integral suggest neotectonic activeness of the southern Saurashtra region. The southern Saurashtra coastal alluvial plains show presence of knick zone, ravines, coastal marine notches, and offset channels/ridges, which testifies the neotectonically active nature of the region. Presence of these features in Miliolites, Middle to Late Pleistocene age, suggests rejuvenation of the landscape post this period.     

Geomorphic expression of late Quaternary sea level changes along the southern Saurashtra coast, western India

Geomorphic expression of land-sea interaction is preserved in the form of abandoned cliffs, marine terraces, shore platforms and marine notches along the southern Saurashtra coast. These features have been used to ascertain the magnitude of sea level changes during late Quaternary. Notch morphology and associated biological encrustation have been used to estimate the magnitude and duration of palaeo-sea strands. Marine notches and other erosive features occurring between 12 and 15 m above the present Biological Mean Sea Level (BMSL) are attributed to the last interglacial corresponding to the Marine Isotopic Stage 5 (MIS-5). However, 6 to 9 m upliftment of the coastal fringe is attributed to this sea level. The second major high sea strand was identified during the mid-Holocene when the sea rose 2 m above the present level. Notches corresponding to this high sea level are recorded 4 to 5 m above the present BMSL.     

Ichnology of the Callovian-Oxfordian rocks of the Katrol hill range,Kachchh, western India

On the basis of distinct lithologic features such as composition, grain size, bedding characteristics and sedimentary structures, six facies were identified in Callovian to Oxfordian rocks exposed southwest of Bhuj, Kachchh. They are interbedded calcareous shale-siltstone (ICSSF), limestone (LF), ferruginous sandstone (FerSF), felspathic sandstone (FelSF), grey shale (GSF) and oolitic limestone (OLF) facies. The rich and highly diversified trace fossils reveal a wide range of animal behaviours represented by dwelling, feeding, crawling and resting structures. Horizontal feeding structures are found abundantly in all lithofacies indicating low wave and current energy and deposition of poorly sorted muddy to sandy sediments. A few coarse layers containing Arenicolites, Ophiomorpha and Skolithos indicate the presence of opportunistic animals (due to their first appearance under harsh conditions) under -intermittently moderate wave and current energy or storm wave conditions (due to coarse grain size and dominance/presence of only vertical trace fossils) in the shoreface zone. Taenidium occurs mainly in the lower shoreface to transitional zone suggesting low to moderate energy conditions. Thalassinoides occurs in middle to lower shoreface settings under relatively low-energy conditions. Zoophycos represents offshore environment, where it occupies the deepest bioturbation levels.The characteristic lithofacies and assemblages of trace fossils in the rocks of the Chari/Jumara Formation indicate a depositional environment fluctuating from the upper shoreface to offshore zone.     

Geomorphological markers of faulting and neotectonic activity along the western Andean margin,northern Chile

In the Atacama Desert, northern Chile, some ephemeral channels are developed in the Plio‐Quaternary alluvial sequence that caps the Neogene Atacama Gravels Formation. Geomorphological studies and high‐resolution digital elevation data (GPS) along a structural transect in the Central Depression are used to document modern growth history of subtle folding and faulting in the fore‐arc region. Outcrop data of the most recent deposits are combined with observations of warped and faulted late Quaternary pediments, alluvial fans and terrace surfaces to propose unsuspected neotectonic processes on the western flank of the Domeyko Cordillera. Neotectonic process recognition is here based largely upon the interpretation of alluvial landforms, drainage organisation and evolution as the intermittent river network shows systematic patterns of course deflections, successive incisions or deposition processes as it encounters the fault scarps or folds in the superficial deposits. This area presents both N–S‐trending active vertical faults in the topographically higher pampas, and N–S‐trending active folding in the lower pampas. These faults seem to accommodate E–W extension and compression that could be related to uplift of the western Andean margin within a compressive context. Uplift may have taken place unevenly over the past few million years after the deposition of the superficial alluvial surfaces that cap the Neogene Atacama Gravels. Copyright © 2003 John Wiley & Sons, Ltd.     

Late Quaternary stratigraphic development in the lower Luni,Mahi and Sabarmati river basins,western India

This study reviews the Quaternary alluvial stratigraphy in three semi-arid river basins of western India i.e., lower Luni (Rajasthan), and Mahi and Sabarmati (Gujarat alluvial plains). On the basis of OSL chronologies, it is shown that the existing intra-valley lithostratigraphic correlations require a revision. The sand, gravel and mud facies are present during various times in the three basins, however, the fluvial response to climate change, and the resulting facies associations, was different in the Thar desert as compared to that at the desert margin; this makes purely lithostratigraphic correlations unviable. It is further shown that the rivers in the Thar desert were more sensitive to climate change and had small response times and geomorphic thresholds as compared to the desert-margin rivers. This is illustrated during the early OIS 1, when the Luni river in the Thar desert was dynamic and showed frequent variations in fluvial styles such as gravel bedload braided streams, sand-bed ephemeral streams and meandering streams, all followed by incision during the early Holocene. The coeval deposits in Sabarmati, however, only show a meandering, floodplain-dominated river. Late Quaternary alluvial deposits in these basins unconformably overlie some older deposits that lack any absolute chronology. Based on the facies types and their associations, and the composition and architecture of the multistoried gravel sheets in the studied sections, it is suggested that older deposits are of pre-Quaternary age. This hypothesis implies the presence of a large hiatus incorporating much of the Quaternary period in the exposed sections     

Intrinsic and scattering attenuation in western India from aftershocks of the 26 January, 2001 Kachchh earthquake

176 vertical-component, short period observations from aftershocks of the M_w 7.7, 26 January, 2001 Kachchh earthquake are used to estimate seismic wave attenuation in western India using uniform and two layer models. The magnitudes (M_w) of the earthquakes are less than 4.5, with depths less than 46 km and hypocentral distances up to 110 km. The studied frequencies are between 1 and 30 Hz. Two seismic wave attenuation factors, intrinsic absorption (Q_i^− 1) and scattering attenuation (Q_s^− 1) are estimated using the Multiple Lapse Time Window method which compares time integrated seismic wave energies with synthetic coda wave envelopes for a multiple isotropic scattering model. We first assume spatial uniformity of Q_i^− 1, Q_s^− 1 and S wave velocity (β). A second approach extends the multiple scattering hypothesis to media consisting of several layers characterized by vertically varying scattering coefficient (g), intrinsic absorption strength (h), density of the media (ρ) and shear wave velocity structure. The predicted coda envelopes are computed using Monte Carlo simulation. Results show that, under the assumption of spatial uniformity, scattering attenuation is greater than intrinsic absorption only for the lowest frequency band (1 to 2 Hz), whereas intrinsic absorption is predominant in the attenuation process at higher frequencies (2 to 30 Hz). The values of Q obtained range from Q_t = 118, Q_i = 246 and Q_s = 227 at 1.5 Hz to Q_t ≈ 4000, Q_i ≈ 4600 and Q_s ≈ 33,300 at 28 Hz center frequencies, being Q_t^− 1 a measure of total attenuation. Results also show that Q_i^− 1, Q_s^− 1 and Q_t^− 1 decrease proportional to f^−ν. Two rates of decay are clearly observed for the low (1 to 6 Hz) and high (6 to 30 Hz) frequency ranges. Values of ν are estimated as 2.07 ± 0.05 and 0.44 ± 0.09 for total attenuation, 1.52 ± 0.21 and 0.48 ± 0.09 for intrinsic absorption and 3.63 ± 0.07 and 0.06 ± 0.08 for scattering attenuation for the low and high frequency ranges, respectively. Despite the lower resolution in deriving the attenuation parameters for a two layered crust, we find that scattering attenuation is comparable to or smaller than the intrinsic absorption in the crust whereas intrinsic absorption dominates in the mantle. Also, for a crustal layer of thickness 42 km, intrinsic absorption and scattering estimates in the crust are lower and greater than those of the mantle, respectively.     

Late Quaternary–Holocene evolution of Dun structure and the Himalayan Frontal Fault zone of the Garhwal Sub-Himalaya,NW India

Dun structures are common in the Sub-Himalayan zone of the Himalaya bounded by the Main Boundary Thrust (MBT) and the Himalayan Frontal Thrust (HFT). They are broad synclinal longitudinal valleys formed as a consequence of the exhumation of the range front of the Himalaya. In the Garhwal Sub-Himalaya, these structures have grown since 0.5 Ma, with the peak activity postdating ∼100 ka. A series of out-of-sequence deformation structures have been identified within the MBT-HFT-bounded Dun structures. They are identified on the basis of geomorphic, post-100 ka stratigraphic, and structural expressions, with activity as young as the early Holocene. To the south of the range front of the Himalaya, uplift has been observed in the Piedmont Zone, with peculiar active tectonic geomorphic expressions. Piedmont sediments of 15–5 ka, determined by Optically Simulated Luminescence (OSL), have been affected by the above uplift. The complete tectonic scenario has been analyzed and an attempt has been made to delineate the sequential evolution of these structures during the post-100 ka period (Late Quaternary–Holocene) in the Himalayan range front.     

Fissures and fractures in the Koyna seismogenic zone,western India

Mn-rich ilmenites (up to 7 % MnO) have been identified in dykes cutting the Malanjkhand porphyry copper mining area in Madhya Pradesh. The dykes are hydrothermally altered and are of tholeiitic affinities. Lamprophyres have been reported from nearby areas. The presence of Mn-rich Ilmenites in the Malanjkhand copper mine dykes and the occurrence of lamprophyres and the pervasive potassium metasomatism in the area strongly suggests a possibility of finding diamondiferous rocks in the area. Such high-Mn bearing ilmenites are associated with diamondiferous deposits in other parts of the world, e.g. Juina kimberlites, Brazil. Mn-bearing ilmenite is considered as an indicator mineral for kimberlite/diamond occurrences. The presence of kimberlite pipes in Raipur district and the association of Mn-rich ilmenite with kimberlites is a fortuitous coincidence for venture-some mining companies. A probable explanation for the origin of manganese layers in the context of ‘rift’ tectonic environment is offered. Also a possible link between the dykes, quartz veins in the Malanjkhand granitic rocks and the copper mineralization is proposed.     

Geochemistry of stream sediments along the western coast of the Gulf of Elat (Aqaba)

One hundred twenty-eight samples of heavy-mineral fractions from sand-size sediments whose mineralogy was previously studied by A. Ayalon, were chosen for this geochemical study. The samples represent the stream sediments along the coastal belt from Elat to Sherm el-Sheikh. This study supplements the geochemical study of A. Zilberfarb and R. Bogoch on the Precambrian terrain of Sinai.The mineral composition of the samples was determined by X-ray diffraction and optical microscopy. In all samples, 14 elements were analyzed: B, Co, Cr, Cu, Ga, Mn, Mo, Nb, Ni, Pb, Sn, Ti, V and Zr. Seven magnetic fractions were separated from twenty of these samples and in these fractions 14 to 20 elements were analyzed, according to the sample. The chemical determinations were mainly by DC emission spectrography.The results were submitted to factor analysis and to association analysis (D. Gill and co-workers). Since the environment is typically arid, there is relatively little chemical weathering. The combined results of both statistical analyses show clearly that three types of source areas can be differentiated: sandstone, metamorphic and granitic terrain. Furthermore, a distinct Mn anomaly was found in the Sherm el-Sheikh area.     

Deciphering condensed sequences: A case study from the Oxfordian (Upper Jurassic) Dhosa Oolite member of the Kachchh Basin,western India

In large parts of the Kachchh Basin, a Mesozoic rift basin situated in western India, the Oxfordian succession is characterized by strong condensation and several depositional gaps. The top layer of the Early to Middle Oxfordian Dhosa Oolite member, for which the term ‘Dhosa Conglomerate Bed’ is proposed, is an excellent marker horizon. Despite being mostly less than 1 m thick, this unit can be followed for more than 100 km throughout the Kachchh Mainland. A detailed sedimentological analysis has led to a complex model for its formation. Signs of subaerial weathering, including palaeokarst features, suggest at least two phases of emersion of the area. Metre‐sized concretionary slabs floating in a fine‐grained matrix, together with signs of synsedimentary tectonics, point to a highly active fault system causing recurrent earthquakes in the basin. The model takes into account information from outcrops outside the Kachchh Mainland and thereby considerably refines the current understanding of the basin history during the Late Jurassic. Large fault systems and possibly the so‐called Median High uplift separated the basin into several sub‐basins. The main reason for condensation in the Oxfordian succession is an inversion that affected large parts of the basin by cutting them off from the sediment supply. The Dhosa Conglomerate Bed is an excellent example, demonstrating the potential of condensed units in reconstructing depositional environments and events that took place during phases of non‐deposition. Although condensed sequences occur frequently throughout the sedimentary record, they are particularly common around the Callovian to Oxfordian transition. A series of models has been proposed to explain these almost worldwide occurrences, ranging from eustatic sea‐level highstands to glacial phases connected with regressions. The succession of the Kachchh Basin shows almost stable conditions across this boundary with only a slight fall in relative sea‐level, reaching its minimum not before the late Early Oxfordian.     

Seismic velocity images of a crystallized crustal magma-conduit (related to the Deccan plume) below the seismically active Kachchh rift zone,Gujarat, India

Natural Hazards - Local earthquake seismic tomography of the Kachchh rift zone (India) using arrival times of P- and S-waves detect a semi-circular region of lower seismic velocities (8–15%...     

Trace fossil assemblages in mixed siliciclastic-carbonate sediments of the Kaladongar Formation (Middle Jurassic), Patcham Island,Kachchh, Western India

The Middle Jurassic rocks of the Kaladongar Formation well exposed in the Kaladongar Hill range of the Patcham Island and Kuar Bet of the Northern Kachchh comprises of ∼450 m thick sequence of mixed siliciclasticcarbonate sediments intercalated with shales. These Mixed siliciclastic-carbonate sediments show wide variation in textural and mineralogical composition and represent genetically related six rock types: micritic sandstone, allochemic sandstone, sandy allochemic limestone, micrtic mudrock, sandy micrite and muddy micrite; which are highly bioturbated and show behaviourally diverse groups of trace fossils. Total 34 ichnogenera are identified, which includes, Arenicolites, Asterosoma, Beaconites, Bergaueria, Chondrites, Cochlichnus, Dactylophycus, Daedalus, Didymaulichnus, Diplocraterion, Gordia, Gyrochorte, Gyrolithes, Ichnocumulus, Laevicyclus, Lockeia, Margaritichnus, Monocraterion, Nereites, Ophiomorpha, Palaeophycus, Phoebichnus, Phycodes, Pilichnus, Planolites, Plug Shaped Form, Protovirgularia, Rhizocorallium, Scolicia, Skolithos, Taenidium, Teichichnus, Thalassinoides and Walcottia. These trace fossils are classified into six morphological groups namely, circular and elliptical structures; simple structures; branched structures; rosette structures; spreiten structures; and winding and meandering structures. These trace fossils are further group into eight assemblages which occurred together into mixed siliciclastic-carbonate sediments, include, Asterosoma assemblage, Gyrochorte assemblage, Rhizocorallium assemblage, Thalassinoides assemblage, Planolites-Palaeophycus assemblage, Phycodes assemblage, Ophiomorpha assemblage and Skolithos assemblage. The recurring pattern of these assemblages through the sequence displays the development of Skolithos and Cruziana ichnofacies and at places the mixed Skolithos-Cruziana ichnofacies which suggest a low wave and current energy conditions with intervening period of high wave and current energy conditions and an intermediate period of stressful environments, respectively. Sedimentological and ichnological data suggest that the deposition of the mixed siliciclastic-carbonate sediments of the Kaladongar Formation took place in the foreshore to offshore environment under fluctuating wave and current energy condition.     

Animal-sediment relationship of the crustaceans and polychaetes in the intertidal zone around Mandvi,Gulf of Kachchh,Western India

Animal-sediment relationships of two benthic communities (Crustaceans and Polychaetes) were studied around Mandvi coast in the Gulf of Kachchh, Western India. This coast consists of many micro-geomorphic landforms in which benthic communities are inhabited and select their niches and produce endemic biogenic structures. Five intertidal subfacies have been described and four types of grounds are identified, based on substrate consistency. 18 species of crustaceans, 15 species of polychaetes and unsegmented worm nemertea have been identified. Crustacean behavioural activities were observed in dunes, beaches and ridge-runnel in the form of burrowing, pellet making, feeding and crawling traces. Pelleted wall lining burrows of the suspension feeder stomatopodean species of Oratosquilla striata are also abundant in runnels. Motile, deposit feeder polychaetes are abundant on the ridges and are occasionally found on the lower reaches of the beaches, while suspension and filter feeders are found in the runnels. Lagoons consist of mainly grouped funnel branched burrows of Oniphus eremita which is identical to ichnogenus Balanoglossites. Nemertea, which are opportunistic algal grazers, have exploited restricted niches for dwelling-feeding purposes and constructed vertical burrow with pentamerous conical mound. The shore platform consists of cemented, calcareous tubes of filter feeder Serpula along with symbiotic encrusters like Ostrea and barnacles. Ichnocoenoses are discussed and three-dimensional ichno-sedimentologic models are reconstructed for Beach, Ridge, Runnel and Lagoon of the Mandvi intertidal zone.