Page:Madras journal of literature and science vol 1 new series 1856-57.djvu/17

1856.] Remarks on the Geology of the Loonar Lake.

In an able statistical memoir of the Circar of Meikher, drawn up by Surgeon Bradley of the Contingent, then on special duty, the opinion is re-advanced and supported by Geological facts, that this singular and wild looking excavation, is the crater of an extinct volcano. On this point, however, there exists amongst Geologists, I believe, some difference of opinion, so that the question may be regarded as still "subjudice." A jagged and picturesque rent exists in the N. E. wall of the supposed crater, down which runs the little stream which passes through a stone channel called the cow's mouth, forming part of a Hindoo temple, which is perched romantically upon a spot near the top of the ravine. Since the destruction of a weir too, during the rains, a large and deep nullah is filled with water which rushes down the ravine. The water as it passes over the almost vertical face of a Trap wall deposits travertin in considerable quantity. Through this great rent, the lava current is supposed by Surgeon Bradley to have found an exit, whence he supposed it to have spread over the surrounding country. Whilst descending the ravine, the rough natural section thus exposed, shows Trap rocks of various kinds, vesicular, compact and amygdaloidal. Masses also of ferruginous trap, weathering red, are seen with seams of chalk, reddish ochre, clay and disintegrated trap having all more or less of a stratiform aspect. During the Resident's recent tour to Hingolee, Loonar, Mominadad, Oodygheer and Beder back to Hyderabad, the whole route with the exception of the syenite and green stone near Hyderabad, and the laterite plateau of Beder lay over an uninteresting country of Trap to the entire exclusion of rock of greater Geological and Paleontological character. In many places, the Trap bears features precisely similar to those observed in the walls and rent of the Natron Lake; at times, the Trap was in solid blocks with vertical seams and irregular horizontal rents—often seen in bowries—again, it was amygdaloidal the nodules being imbedded in concentric laminæ of disintegrated trap and argillaceous shale, the beds being laid over chalk, argillaceous schists, marls, red ochre and green earth—again, it appeared in rude, but distinct strata, almost as regular as the layers of stones in a wall—again, it appeared disor-