MOOK, STUDY OF THE MORRISON FORMATION 159 



9). The principal mineral ingredient in the Morrison sediments is 

 quartz. Other materials usually or often present are calcite, kaolin, iron 

 oxides, mixed carbonates, gypsum and feldspar. Mica and volcanic ash 

 are present in very small amounts. 



10). The larger quartz grains are usually well rounded: the smaller 

 ones are often angular. 



11). The iron oxides usually occur as interstitial material between fine 

 quartz grains, and sometimes as a staining of fine-grained binding matter. 

 In some cases it is uniformly distributed, and in other cases it is scattered 

 in patches. 



13). The limestones are thin, often very pure calcite or dolomite, and 

 consist almost entirely of very fine-grained material. They are some- 

 times argillaceous and sandy. 



13). The sandstones are often nearly pure quartz; when fine-grained 

 they sometimes have interstitial materials of iron oxides, kaolin and 

 mixed carbonates; when coarse they are often extremely calcareous, and 

 sometimes arkosic. 



14). The arkosic sandstones usually occur near the base of the forma- 

 tion. They are occasionally found in the middle beds, and are rare near 

 the top. 



15). The color of the rocks of the formation varies greatly, often in 

 short distances, so that the formation was formerly called the ^'Variegated 

 Beds." This variegated character is sometimes present in a hand speci- 

 men. There is often a pronounced color banding in the formation. 



Gray and purplish red are the usual colors, but green, white, blue, 

 yellow and black are also often present, and all these colors grade into 

 each other in a complex fashion. 



16). The coarse sandstones are usually gray or white. The finer clays 

 and grits may be either gTeen, gray, white, blue, red or dark brown. The 

 green clays are often finer than the red or brown grits. 



17). The flora of the formation is of such a nature as to indicate a 

 warm and moist climate at the time of deposition, in some areas at least. 

 This flora is not especially alnindant, however. 



18). The invertel'rate fauna consists of fresh-water types. They be- 

 long to genera having a wide geologic range. 



19). The vertebrate fauna is composed of aquatic, amphibious, ter- 

 restrial and aerial forms. The flsh were aquatic, of course. The habitat 

 of the sauropod dinosaurs has been the' subject of controversy ; some 

 writers have held that they were exclusively terrestrial, others that they 

 were exclusively aquatic, and still others that they were amphibious. The 

 latter theory seems the most proliable. They certainly possess aquatic 



