Javed N. Malik

CALCRETES IN SEMI-ARID ALLUVIAL SYSTEMS : FORMATIVE PATHWAYS AND SINKS

Late Quaternary deposits in Gujarat, western India show an abundant development of calcretes. Three major sinks of carbonate in the alluvial deposits are recognized: (1) groundwater calcretes, (2) pedogenic calcretes, and (3) calcrete conglomerates. Groundwater calcretes originate from carbonate-saturated waters travelling preferentially along stratification planes. Pedogenic calcretes form through soil-forming processes typically in extra-channel areas. Calcrete conglomerates occur as ribbons, sheets and lenses due to the reworking of both pedogenic as well as groundwater calcretes. As a result a pathway of calcretization develops that has the route: groundwater calcrete to pedogenic calcrete to calcrete-conglomerate. The formation of pedogenic calcretes over sediments containing groundwater calcretes demonstrates that (1) apart from aeolian dust, river waters are also a major source of carbonate, and (2) pedogenic carbonates may attain large sizes at accelerated rates due to the presence of pre-existing groundwater calcretes. Consequently, the maturity of a soil may be overestimated if determined by following established morphogenetic sequences.

Sedimentology of the Narmada alluvial fan, western India

Abstract The Narmada alluvial fan is one of the worlds largest, with an axial length of 23 km. The architecture is dominated by debris-flow deposits (Gms facies). Matrix support, a clay content of 3% and clast contact indicate that the clast-support mechanism resulted from a combination of buoyancy and dispersive pressure. The other faci facies (GSh), planar cross-stratified gravel facies (Gp1 and Gp2), sand-sheet facies (Sm), and trough cross-stratified sand facies (St). Gms, GSh and Sm facies are debris-flow and sheet-flow deposits that aggraded the fan, whereas Gp1 and St are channel bars and channel fills that dominated the fan between major flood events. The fan is characterised by subrounded to rounded clasts. The rounding is due to the elongated catchment area upstream of the fan apex, as clasts are rounded during prolonged bed load transport and are temporarily arrested upstream of the fan apex as channel bars. These clasts are remobilized and entrained in debris-flows on the fan during events of anomalous discharge (storm events). The basalt clasts show a progressive fall in maximum clast size from 150 cm to 10 cm away from the fan apex. The Narmada river exhibits discharges of up to 60,000 m3/s, but, due to reconfinement of the feeder channel resulting from tectonic reactivation of pre-existing lineaments during the Late Pleistocene, this does not aggrade the fan. Tectonism has influenced the location of the depositional site, has provided the necessary physiographic contrast, and has played an important role in the erosion of the fan, whereas climate-controlled primary and secondary processes have determined the nature of alluvial architecture.

Geologic evidence for two pre-2004 earthquakes during recent centuries near Port Blair, South Andaman Island, India

Coastal stratigraphy near Port Blair, Andaman Islands, where the A.D. 2004 Sumatra-Andaman earthquake was accompanied by ∼1 m of subsidence, provides evidence for two prior earthquakes, perhaps both from the past 400 yr. The first of these (event I) is marked by an abrupt mud-over-peat contact best explained by subsidence similar to that in 2004. Event II is evidenced by an overlying chaotic layer composed of mud clasts in a sandy matrix that is connected with feeder dikes. These mud clasts, probably produced by liquefaction, are capped by laminated sand and mud that we ascribe to an event II tsunami. Radiocarbon ages of plant remains in the peat give discordant ages in the range 100 B.C. to A.D. 1950. Event I probably resembled the 2004 Sumatra-Andaman earthquake in that it was accompanied by subsidence (as much as 1 m) but not by strong shaking near Port Blair. If event II was the A.D. 1762 Arakan earthquake, the laminated sand and mud provide the first evidence that this earthquake was associated with a tsunami.

Evidence of paleoearthquakes from trench investigations across Pinjore Garden fault in Pinjore Dun, NW Himalaya

The Pinjore Garden Fault (PGF) striking NNW-SSE is now considered one of the active faults displacing the younger Quaternary surfaces in the piggyback basin of Pinjore Dun. This has displaced the older Kalka and Pinjore surfaces, along with the other younger surfaces giving rise to WSW and SW-facing fault scarps with heights ranging from 2 to 16 m. The PGF represents a younger branch of the Main Boundary Thrust (MBT) system. An ~ 4m wide trench excavated across the PGF has revealed displacement of younger Quaternary deposits along a low angle thrust fault. Either side of the trench-walls reveals contrasting slip-related deformation of lithounits. The northern wall shows displacement of lithounits along a low-angle thrust fault, while the southern wall shows well-developed fault-related folding of thick sand unit. The sudden change in the deformational features on the southern wall is an evidence of the changing fault geometry within a short distance. Out of five prominent lithounits identified in the trench, the lower four units show displacement along a single fault. The basal unit ‘A’ shows maximum displacement of aboutTo = 2.85 m, unit B = 1.8 m and unit C = 1.45 m. The displacement measured between the sedimentary units and retro-deformation of trench log suggests that at least two earthquake events have occurred along the PGF. The units A and D mark the event horizons. Considering the average amount of displacement during one single event (2 m) and the minimum length of the fault trace (~ 45 km), the behaviour of PGF seems similar to that of the Himalayan Frontal Fault (HFF) and appears capable of producing large magnitude earthquakes.

ACTIVE FAULTING AND DEFORMATION OF QUATERNARY LANDFORM SUB-HIMALAYA, INDIA

Active Faulting and Deformation of Quaternary Landform Sub-Himalaya, India Landforms developed across terrain defining boundary the Main Boundary Thrust (MBT) have imprints of recent tectonic activity. Depositional landforms such as colluvial fan bear signatures of later phases of tectonic activity in the form of faulting of colluvial fan deposits and development of fault scarps. Tectonic geomorphology applied to the MBT zone suggests recent subsurface activity along the MBT and its splay thrusts. Present day tectonic activity of MBT is indicated by ground creeping, thrusting of Lower Siwalik rocks over recent colluvial fan deposit, aligning of series of lakes along splay faults and laterally along a fault, deflected streams, fault scarps and waterfalls. In the present paper we are addressing the tectonic situation in the foothill region of southeastern Kumaun Sub-Himalaya, India based on detailed field work carried out in the region which brought forward some outstanding morphotectonic evidence of neotectonic activities in the MBT zone.

Four major unknown active faults identified, using satellite data, in India and Pakistan portions of NW Himalaya

New mapping through geomorphic analysis of tectonic landforms using a variety of freely available satellite data, including shuttle radar topography and Google Maps, has revealed four major curvilinear ~NW–SE trending faults in NW Himalaya regions of India and Pakistan. From north-west to south-east, these are named as Mawer, Tunda, Gulmarg, and Mughal Road fault zones. Some of these faults show evidence of oblique faulting where thrusting is accompanied by a small component of sinistral strike–slip faulting, and this possibly increases towards south-east. The active nature of deformation on these faults is demonstrated by occurrence of triangular facets, fault rupture scarps, topographic breaks, displaced ridges, shutter ridges, deflected drainages, plus uplift and back tilting of Holocene sedimentary deposits. This is further supported by the fact that these fault traces truncate the previously mapped active structures such as Kashmir basin/Balapore fault and main boundary thrust. The abrupt termination of most of these faults in north-west indicates a strong structural control. These faults are active, and their dimensions and geometrical configurations indicate their potential to host major earthquakes that could be similar or greater than what we witnessed during Kashmir earthquake of 2005. Further, active deformation is also mapped within Udhampur Piggyback basin, which lies within the Riasi fault system in Jammu and Kashmir, NW Himalaya. The emergent thrusting further suggests splay faulting from one of the branches of the Riasi fault system (Mandili-Kishanpur thrust). The structural configuration of the basin indicates a possible structural control on the formation and deformation of the basin. The geomorphic expression of active faulting is manifested in the overall morphology of the oval-shaped basin (similar to Kashmir basin in NW Himalaya). The shape is structurally controlled by faults as the whole of the basin is riding on Riasi fault system. Within the valley, the active faults are only visible on the ~SE portion. This has divided the basin into two distinctive geomorphic divisions: SE and NW domains. These domains are delineated by a structural break that could be ~NE–SW trending fault zone because the mapped faults do not continue beyond this topographic break in the basin. And since the SE tectonic domain is faulted, the streams are deeply incising into the bedrock forming deep canyons. The tributaries are short because their lengths are trimmed by the faults. Thus, the tributaries on the hanging wall have permanently lost their headwater source and are orphaned. Such geomorphic features are not visible in the NW domains, which have not been faulted, and thus, the streams are following the natural slope. All the streams feed the basin merge into a major stream (Tawi River) that cuts through the anticlinal ridge of Suruin–Mastgarh anticline. This river roughly follows the interpreted ~NE–SW trending topographic break, which could mean that it follows a fault. Such an interpretation is backed by the evidence that the anticlinal ridge is only broken at this portion of the ridge.

GCP collection for corona satellite photographs: Issues and methodology

Use of high-resolution and historic CORONA satellite photographs for mapping and other purposes requires Ground Control Points (GCPs), as ephemeris data and image parameters are not available. However, the alterations in landscape in last 34 years (i.e., since the acquisition of these photographs) prevent identification and collection of large number of GCPs in the field. This paper presents a methodology for collection of GCPs for CORONA photographs. The advantages and limitations of the methodology are discussed. For a study site, situated in Siwaliks and Lower Himalayas, the GCPs were identified in CORONA photographs and their WGS84 coordinates were estimated through a process of datum transformation and georeferencing. Estimated GCP coordinates from the topo sheets and 2D and 3D views of photographs, helped in identifying the GCP locations in field, which were observed using DGPS. Investigations were carried out to relate Differential Global Positioning System (DGPS) accuracy with base line length and time of observation. Abase line of 350 km and half an hour observation were found appropriate to yield accuracy in GCP collection by DGPS method, which conforms to CORONA resolution of 3 m.

Use of satellite data for tectonic interpretation, nw Himalaya

Mountain topography is the result of highly scale-dependent interactions involving climatic, tectonic and surface processes. Tectonic geomorphology deals with the geodynamics and geomorphic manifestation of crustal deformation processes. In Himalaya, bulk of the relief in mountainous region has been formed by uplift along thrust faults striking sub-parallel to the trace of the thrust zones. Therefore, there is an intimate link between uplift rates, material redistribution rates due to geomorphic processes, and the morphology of the area. By quantifying features the tectonic uplift rates and constrains geomorphic process rates can be inferred. To understand the complex interrelationship of these elements in regional scale, there is a need to develop new approaches and methodologies. With significant improvement in resolution of available digital terrain data and computing resources, the evaluat ion of morphotectonic in a Geographical Information System (GIS) environment tends to be quantitative and more precise.

Ground penetrating radar investigations at Ahichhatra: An attempt to identify buried subsurface structures

Ahichhatra, is 20 km from Bareilly district, Uttar Pradesh, one of the most ancient settlements in India. It encompasses differential accumulation of cultural and structural deposits beginning from 2500BC-1200AD. Ground Penetrating Radar (GPR) survey, involving both 2D & 3D profiling, helped in finding the buried structures at the site and also in understanding the pattern of occupancy. GPR and surface investigations carried out at Ahichhatra revealed slumped and displaced walls, warped surfaces, buried pavements and ruins of various foundations that spread over a wide range of area. These evidences are indicative of a large magnitude earthquake related damage and deformation, most likely having earthquake source in Himalayan foothills.

Ground-Penetrating Radar Investigations along Hajipur Fault: Himalayan Frontal Thrust—Attempt to Identify Near Subsurface Displacement, NW Himalaya, India

The study area falls in the mesoseismal zone of 1905 Kangra earthquake (Mw 7.8). To identify appropriate trenching site for paleoseismic investigation and to understand the faulting geometry, ground-penetrating radar (GPR) survey was conducted across a Hajipur Fault (HF2) scarp, a branching out fault of Himalayan Frontal Thrust (HFT) in a foot hill zone of NW Himalaya. Several 2D and 3D profiles were collected using 200 MHz antenna with SIR 3000 unit. A 2D GPR profile collected across the HF2 scarp revealed prominent hyperbolas and discontinuous-warped reflections, suggesting a metal pipe and a zone of deformation along a low-angle thrust fault, respectively. The 3D profile revealed remarkable variation in dip of the fault plane and pattern of deformation along the strike of the fault.