Late Cretaceous Vicariance in Gondwanan Amphibians

Overseas dispersals are often invoked when Southern Hemisphere terrestrial and freshwater organism phylogenies do not fit the sequence or timing of Gondwana fragmentation. We used dispersal-vicariance analyses and molecular timetrees to show that two species-rich frog groups, Microhylidae and Natatanura, display congruent patterns of spatial and temporal diversification among Gondwanan plates in the Late Cretaceous, long after the presumed major tectonic break-up events. Because amphibians are notoriously salt-intolerant, these analogies are best explained by simultaneous vicariance, rather than by oceanic dispersal. Hence our results imply Late Cretaceous connections between most adjacent Gondwanan landmasses, an essential concept for biogeographic and palaeomap reconstructions

Selective Enrichment and Sequencing of Whole Mitochondrial Genomes in the Presence of Nuclear Encoded Mitochondrial Pseudogenes (Numts)

Numts are an integral component of many eukaryote genomes offering a snapshot of the evolutionary process that led from the incorporation of an α-proteobacterium into a larger eukaryotic cell some 1.8 billion years ago. Although numt sequence can be harnessed as molecular marker, these sequences often remain unidentified and are mistaken for genuine mtDNA leading to erroneous interpretation of mtDNA data sets. It is therefore indispensable that during the process of amplifying and sequencing mitochondrial genes, preventive measures are taken to ensure the exclusion of numts to guarantee the recovery of genuine mtDNA. This applies to mtDNA analyses in general but especially to studies where mtDNAs are sequenced de novo as the launch pad for subsequent mtDNA-based research. By using a combination of dilution series and nested rolling circle amplification (RCA), we present a novel strategy to selectively amplify mtDNA and exclude the amplification of numt sequence. We have successfully applied this strategy to de novo sequence the mtDNA of the Black Field Cricket Teleogryllus commodus, a species known to contain numts. Aligning our assembled sequence to the reference genome of Teleogryllus emma (GenBank EU557269.1) led to the identification of a numt sequence in the reference sequence. This unexpected result further highlights the need of a reliable and accessible strategy to eliminate this source of error

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 NFIR, incision ages on, channel fills and valley fill terraces progressively decrease from similar to 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 similar to 12 mm/a. The KMF and the South Wagad Fault (SWF) represent the bounding faults of a transtensional basin that formed during the initial rifling. 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 NFIR 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. (c) 2006 Elsevier B.V

FT-IR spectroscopic investigation of hydrous components in sillimanite from Eastern Ghat Granulite Belt, India

FT-IR spectra of sillimanite samples from high grade regionally metamorphosed rocks belonging to the granulite terrain (amphibolite to pyroxene granulite facies) deciphers prominent OH features. Heating experiments indicate growth of prominent band at 3161cm(-1). Heating above 1000 degrees C all OH features disappear in intensity into broad features with slight shift of bands towards lower energies. Complete dehydration requires temperatures above 1000 degrees C. Coexistence of boron and OH features are also observed in all sillimanite samples. The high temperature behaviour of sillimanite from the granulite terrain discerns that the hydrous species in sillimanite were incorporated much below 700 degrees C, however, secondary hydration due to pegmatite activity retrograde metamorphism and migmatisation is not ruled out. Thus a near anhydrous condition were probably not achieved during the granulite facies metamorphism in Eastern ghat granulite terrain

Colouration in natural beryls: A spectroscopic investigation

Beryl samples from Badmal mines, Orissa were studied by electron spin resonance, optical absorption and Mossbauer spectroscopy. It was found that on artificial irradiation, colourless beryls from Orissa turned to shades of yellow-green. On subsequent heating at 300 degrees C, the hue changed to yellow and upon further heating at controlled conditions they turned to a more desirable sky blue, accounting for value addition. Continued heating above 500 degrees C, however, rendered them colourless. Similar studies were also carried out on natural yellow, blue and green beryls from Orissa, all of which acquired a greenish hue on irradiation and turned colourless on heating to >5000 degrees C. Electron probe microanalysis of beryls showed iron as the major transition element impurity. ranging in concentration between 0.5 to 0.7wt%. Investigations using electron spin resonance, optical absorption spectroscopy and Mossbauer spectroscopy reveal that: colours produced were on account of Maxixe-type defect centres as well as radiation-induced oxidation of Fe2+ to Fe3+ ion and associated charge transfer process. It is interesting to note that the yellow and blue colour produced on irradiation as well as post irradiation heating showed similar hue to that of the natural ones, both having formed on account of similar charge transfer process. Thus, it can be inferred that natural yellow, blue and green colours in beryls comprising low iron impurities are due to prolonged irradiation in nature

ESR dating of interfault gypsum from Katrol hill range, Kachchh, Gujarat: Implications for neotectonism

This article presents chronological investigations on interfault fibrous gypsum using the technique of Electron Spin Resonance (ESR) dating, essentially to demonstrate the robustness of the technique as a dating tool on fibrous gypsum precipitates in a semi-arid region. Samples of fibrous gypsum collected from Katrol hill range, Kachchh consist of those from fractures and bedding planes, and those along the inferred fault plane. The slow progressive uplift along the region resulted in erosion, unloading and dissolution of near-surface evaporite deposits and formation of extensional joints parallel to bedding and across. These openings became favourable sites for the fibrous gypsum to develop perpendicular to the wall of factures as well as fault plane. ESR chronometry. studies deduce that gypsum growth along the bedding plane and fractures took place around 300 ka, while ESR dating studies on fault plane gypsum indicate an age around 70 ka. The young age of the normal fault plane indicates that it developed on account of the ongoing compressive stresses which resulted in normal faults perpendicular to the principal stress and later got immediately filled by sulphate-rich solutions. The ongoing compressive stresses active on the region have finally resulted in further uplift of the footwall back limb to its present topography

Channel constituents of alkali-poor Orissan beryls: An FT-IR spectroscopic study

The Fourier transform infrared (FT-IR) spectra of four coloured beryls, both in single crystal and powder form, were studied at room temperature to characterize the volatile constituents of beryls from Badmal mines of Orissa state, Among the four coloured beryls (colourless, blue, green and yellow), the green beryl shows predominance of type-II H2O. Presence of sodium and cesium molecules associated with OH- group and CO2 as common channel constituent is also deciphered. Fourier self-deconvolution (FSD) technique is applied to observe weak shoulders and classify beryls based on substitution. While the c/a ratio of 0.9994-0.9996 indicates beryls to be of 'tetrahedrally substituted', the FT-IR study in the structural vibration indicates them to be of 'normal type'