MANSFIELD: ROXBURY CONGLOMERATE. 127 
Medlicott and W. T. Blanford, R. D. Oldham, C. D. White, and 
others. The main characteristics as summarized by White (p. 302- 
303) are quoted in substance as follows:—The Talchir boulder beds 
underlie coal-bearing strata, are often 500-800 feet thick and consist 
of clays, fine silts, boulders, sandy shales, conglomerates, and soft 
sandstones. They are distinguished everywhere by semi-angular and 
somewhat rounded pebbles, boulders and rock masses of quartzite, 
Vindhyan rocks, granite, gneiss, and metamorphics. The boulders 
are usually foreign to the localities where found, are generally but 
slightly rounded and are smoothed, furrowed, and striated in parallel 
straight lines. Often the boulders are faceted, perfectly polished 
and striated in two or more directions, similar to fragments shaped 
and marked by glaciers. The boulders are not at the angles of repose 
incident to current action, but lie at all angles, embedded in silt too 
fine to admit other explanation than the action of floating ice. In 
the neighborhood of Madras quartzite boulders with a volume of 
800-1,000 cubic feet occur in a matrix of friable clay. At another 
locality a mass of rock 10743 feet is found which is similar to no 
rock nearer than the Arvali Mountains, 150 miles south. 
This description may be supplemented by a few additional details 
taken from the accounts of R. D. Oldham. The matrix of the boulder- 
bed is described (b, p. 468) as “always tolerably and often extremely 
fine grained... .itself distinctly stratified and interstratified with well- 
bedded rock. Through this are scattered blocks of all sizes, always 
embedded in and well separated by the matrix. Where finely lami- 
nated, the bedding is observed to bend down under and arch over the 
included fragments. The matrix was deposited in quiet water. 
Driftwood and volcanic agency are excluded; the only adequate 
explanation is floating ice. Many boulders are striated and in two 
localities the beds rest on a striated roche-moutonnee surface.” The 
soft sandstones accompanying the Talchir group contain undecom- 
posed feldspar (ibid., a, p. 157). 
Glacial boulder-beds of corresponding age have been described 
from several rather widely separated localities in India and similar 
rocks have been reported from Kashmir (ibid., a, p. 135). It seems 
therefore that the glacial formation extends over a wide area in that 
region. 
-— Australia. Boulder-beds similar to those of India occur in 
New South Wales. “Large boulders of foreign rock with distinctly 
glacial smoothings and striations occur, embedded in fine grained silt 
along with delicate Fenestellae and bivalves whose valves are still united 
S 
