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Gauri Dole ¹, V. V. Peshwa ¹, Vivek S. Kale ¹

Affiliations
1 Department of Geology, University of Pune, Pune 411007, IN

Abstract

Palaeoseismic evidence is recorded for the first time from the upland region near the crest of the Deccan plateau. Some of the soft-sediment deformation structures from Quaternary sediments in the Chandanapuri valley are interpreted as seismites. These sediments rest nonconformably upon the Deccan Traps and are inherently anomalous vis-a-vis their location in the river valley. Based on various features and their position in the succession of the sediments, these seismites are provisionally attributed to a single event with an inferred magnitude > 6.5 M, which occurred 5000 - 7000 years ago. This report highlights the need to re-evaluate the traditional perception of the aseismic nature of the main Deccan plateau.

Keywords

Palaeoseismology, Deccan Plateau, Quaternary Sediments, Seismites.

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Raymond A. Duraiswami ¹, Gauri Dole ², Ninad Bondre ³

Affiliations
1 A/6 Gurudut Housing Society, Srinagar, Kalewadi Phata, Rahatani, Pune - 411 017, IN
2 Department of Geology, University of Pune, Pune - 411 007, IN
3 Department of Geology, Miami University, Oxford, Ohio - 45056, US

Abstract

A ∼9.75 km long, sinuous structure exposed near village Songir, east of Dhile has been previously interpreted to be a lava tube on the basis of remote sensing and field checks. Detailed field investigations, however, reveals an overlapping sequence of P-Type lobes and sheets, constituting a small compound pahoehoe flow, whose sinuous form has been guided by Pre-Existing topography. The Songir structure is undoubtedly a small, Sheet-Flow that propagated by repeated branching of toes and lobes that have been emplaced through the mechanism of inflation. This pahoehoe flow does not bear any resemblance to a lava tube. The study of the Songir structure reiterates the fact that greater caution should be exercised while identifying similar structures in the large and ancient Continental Flood Basalt provinces.

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Raymona D. Duraiswami ¹, Ninad Bondre ², Gauri Dole ², Vinit Phadnis ²

Affiliations
1 Department of Geology, University of Pune, A-6, Gurudut Housing Society, Kalewadi Phata, Srinagar, Rahatani, Pune - 41 1 017, IN
2 Department of Geology, University of Pune, Pune - 411 007, IN

Abstract

The dimension, morphology and structure of seventeen flow-lobe tumuli in pahoehoe flows from western Deccan Volcanic Province are collectively reported here for the first time. The flow-lobe tumuli documented here are generally found in hummocky pahoehoe. The presence of flow-lobe tumuli in pahoehoe flows is consistent with tubefed nature of these flows and suggests emplacement by the mechanism of inflation. The flow-lobe tumuli are of various shapes and sizes. In general, the length of flow-lobe tumuli from the present study ranges from 2.8 to 40 m and their widths range from 2.76 to 28.5 m. The ratio of crust width to tumulus width equals unity indicating that uplift did not involve lateral compression. Variations in shape and size of flow-lobe tumuli are attributable to variations in site characteristics such as nature of substrate, degree of slope, interference of other lobes and local rate of lava supply. Similarly, the study of orientation and location of flow-lobe tumuli within flows reveals that locally defined, random factors control the orientation of flow-lobe tumuli. Their presence generally towards the terininal ends of flow fields suggests that they seldom form over the clogged portions of distributory tubes or pathways. Thus, localized inflation due to blockage of lava tube results in formation of flow-lobe tumuli. The three-tiered (crust-core-basal zone) in ternal structure of the flow-lobe tumuli, resembling the typical distribution of vesicles in P-type lobes, confirms emplacement by the mechanism of inflation. Considering the age of the Deccan Volcanic Province (64-65 Ma) it is most probable that the structures described here may be amongst the oldest recognized examples of lava inflation.

Keywords

Pahoehoe Flows, Flow-Lobe Tumuli, Inflation, Deccan Volcanic Province, India.

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S. Viswanathan ¹, K. S. Misra ², Gauri Dole ³, Ninad Bondre ⁴, Raymond A. Duraiswami ⁵, Vivek S. Kale ⁶

Affiliations
1 10, Bapuji Apts., Rajendra Prasad Raod, Dombivli (East) - 421 201, IN
2 Geological Survey of India, Alandi Road, Phule Nagar, Pune - 411 006, IN
3 238, Narayan Felli, Pune, 411 030, IN
4 114 Shideler Hall, Department of Geology, Miami University, Oxford, Ohio 45056, US
5 A16 Gurudut Housing Society, Srinagar, Kalewadi Phatta, Rahatani, Pune - 411 017, IN
6 Kalyani Net Ventures Ltd., Pune, IN

Abstract

No Abstract.

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