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XXXIX. — Geological Notes on part of Mazunderan. 

 By CHARLES M. BELL, M.D. 



[Read January 17, 1838.] 



lEHRAN stands on an alluvial plain consisting- chiefly of debris of lime- 

 stone and trap rocks, (see Map, p. 381.) The high range immediately to the 

 north of the city is composed of fine-grained lithographic limestone*; the 

 strata dippings to the north and resting upon porcelain-stone, which passes into 

 serpentine and porphyretic claystonef. The hills to the south-east of Tehran 

 and overhanging the ruins of the city of Rai, are formed of limestone repo- 

 sing on trap. 



From Tehran the soft, lithographic limestone extends nearly to the village 

 of Demavend; but the sandstone of the subjacent coal-formation is occasion- 

 ally exposed. A little to the westward of the village, the ground rises consi- 

 derably ; and in the ranges of mountains, both north and south of the road, as 

 far eastward as the caravanserai of Dalee chaee, nothing is seen but limestone 

 resting on trap. In the bed of the river, we passed some upraised strata of 

 altered shale, resembling coked coal; and upon the opposite bank we observed 

 a loose conglomerate of fragments of limestone and trap, imbedded in what 

 appeared to be dried mud, or detritus of the above-mentioned limestone;}:. 



* This stone, which takes a beautiful surface, has lately been used in the lithographic presses at 

 Tehran ; and it forms an excellent cement under water. Associated with a blue variety it ex- 

 tends over an immense tract to the N. and N.W. of Tehran, on the southern aspect of the chain of 

 Elboorz. It there generally rests upon shale and red sandstone, which again overlie a compact 

 limestone. (This rock is considered by the author to be mountain-limestone. — Ed.) 



f The rock which forms the substratum of the greater part of the range of the Elboorz is trap, 

 passing into every possible variety of basalt, greenstone, claystone, claystone- porphyry, pitch- 

 stone, pitchstone-porphyry, serpentine, &c. 



J From its appearance in different parts of the country, I imagine this formation to be the remains 

 of great volcanic floods of mud, which carried along large fragments of rock, and were spread un- 

 equally over the surface ; and that they have been more or less removed by denudation. In the pre- 

 sent route, we met with it in several places, occupying low hills and valleys, in general unconform- 

 ably with the strata beneath ; and in other parts of Persia we found a similar formation covering the 

 lower grounds, near lofty ranges of limestone elevated upon trap, — for instance, in the valley of the 



