17'2 CAWHdNlKIOKOl'S KdKMA'I'KINS AND KAI'NAS ii|' ( 1 1|,( IK A I « i. 



dark i'iU'l)oniU'0()iis ;iih1 calcarcHJUs .slialo.s and tliin liiii('stoii''.~. 'I'hc thickness varies 

 fVdli) Ion to r).")0 IVet, a raiiy'e of lueasurenieiit wllic^h is accniintiMl foi- hy Kidl'idii'e l>y 

 tiie Tart thai it I'olhiws a marked miconformity. Its fossils ;trr iilmndant. and of llie 

 Coal Measures tv[)e. The Maroon coiie'lonK^'ate is t'aken lo l"'L:,in with thin heds of 

 calcareous grits dili'erent fi'oni the constituents of the \\'elici- formation, and to end 

 with " the unconfonnity overlying the Gunnison sandstone."' though in this last 

 statement "overlying" is clearly a misprint for imd/'r/t/nii/. 'i'he maximum tlii(d\- 

 ness is thus 4,500 feet. A lower and an upper division of ihr formation are recog- 

 nized. "The lower division is an alternating series of yellowish-gray grits, thin 

 limestones, and shale beds, reaching 2,000 feet in thickness in rJieir greatest develop- 

 ment along lower Cement Creek. The grits consist of grains ;ind pebbles of quartz 

 and limestone, with a calcareous and somewhat ferruginous cenient."" The limestone 

 pebbles vary in size up to 3 or-i inches, and frequently contain (Joal Measures fossils. 

 This occurrence of Upper Carboniferous fossils in pebbles in the Maroon conglom- 

 erate is an important and well-established fact. Station I'Mot;. near Cement Creek, 

 in our collections, seems to be an instance of this association, and the fauna, it will 

 be seen, is clearly a Pennsy Iranian one. It is somewhat unexpected that the fauna 

 of these jDebbles is the native Maroon fauna and not thai of the eroded Leadville 

 limestone or of the Weber formation. The limestones of rhe lower division occur 

 in beds from 1 to 15 feet thick, are of bluish-gray color, and are frequently fossil- 

 iferous. The upper division, which has a maximum thickness of about 2,500 feet, is 

 composed of alternating beds of conglomerate and sandston<'. with some shales and 

 occasional limestone beds. The pebbles of the conglomerate consist largely of red 

 granite and schist from the Archean areas, with representatives of quartzites and 

 limestones of the older sediments. The upper division is ')f a peculiar red or 

 chocolate color. It is found in greatest thickness in the northern part of the 

 Crested Butte quadrangle, and is very greatly decreased in rhe southern portion. 



In the Aspen district the Weber foi*mation consists of n series of thin-bedded 

 carbonaceous limestones and calcareous shales. The typical rock is a black limestone, 

 thin bedded, and aphanitic. The maximum thickness is reported at not nmch less 

 than 1,000 feet. "Above the Weber formation comes a, great thickness of mixed 

 arenaceous and calcareous sediments forming impure grits and thin-bedded shaly 

 limestones. This formation is calcareous and thin bedded Ht tirst, but becomes more 

 massive and arenaceous farther up. The general color is a peculiar dark red 

 * * *." " "The purplish-red beds pass upward into moiv niassive and fine-grained 

 sandstones which are more purelv siliceous in composition and of a bright brick-red 

 color." "The change to these Red Beds, however, is not iibrupt, and does not indi- 

 cate anv break in the sedimentation.'"' There is a basal u-rav bed of the Maroon 



1' U. S. Geol. Surv., Mon., vol. 31, p. 33. . '■ Ibid, p. 34. 



