UPPER CRETACEOUS. , 667 



Within the limits of this area the great body of the Fox Hills is but iadefinitely distinguished 

 from the Pierre. In mild contrast with the latter its shales are yellowish instead of slate colored 

 and are also more arenaceous. * * * ^j^g topmost stratum of the Fox HiUs is, however, 

 a very definite feature in the stratigraphy. For niany feet below it there are occasional sand- 

 stone beds, and the intervening shales are highly sandy, but at the top is a continuous bed of 

 sandstone 40 feet thick. 



The Laramie outcrops in the southeast corner of the area. Within the limits here defined 

 this formation consists essentially of (1) sandstones at the base, (2) sandstones alternating with 

 shales and coal overlying, (3) sandstones above the coal, and (4) clays, containing isolated sand- 

 stone beds and lignitic streaks. * * * The basal sandstones are exposed at various places 

 in the Marshall coal field, but best of all at White Rocks, on the eastern border of the area, 

 mapped. Here the bold sandstone escarpment comprises two distinct and massive beds, 

 whose topographic effect, however, is that of a single stratum contiauous with the Fox HjUs 

 sandstone beneath. The lower Laramie sandstone is 40 feet thick, equaling the underlying 

 Fox Hills sandstone, while between the two are a few feet of thinly laminated sandstones, varying 

 to a lignitic shale. The second and thicker stratum of Laramie is separated from the first by 

 gray shaly sands, inclosing 10 inches of Hgnitic shale and above 10 inches of coal. Both Laramie 

 beds are clearly distinguished from the Fox HjUs by their gray or white color and coarser grain. 

 They are composed of coarse quartz sand and in addition always show some black specks of an 

 undetermined mineral. The two sandstones differ in the following respects: The upper is 

 distinctly whiter and, where exposed along bedding planes (and to a less degree on fracture 

 planes), the surface is marked by weathered-out cracks, making polygonal patterns a few feet 

 across. Both strata are weakly cemented and noncalcareous but contain giant concretions 

 which are very calcareous, hard, and, on weathered surfaces, are stained brown with iron oxide. 

 The 75 feet of thinner-bedded sandstones above, containing some shale and coal, are best seen 

 at Marshall. The shales occur at frequent intervals and are often hgnitic. The one workable 

 coal seam is sometimes at the top of this division but again is overlain by 5 or 10 feet of shales 

 and thin sands ; all, however, lie below the more persistent sandstone referred to under (3) above. 

 Aside from the coal seam, no horizon above the basal sandstones is more definite than the 

 Ostrea glabra zone, which occurs 15, or 20 feet from the base of the series. The sandstone above 

 the coal is not unlike the second massive bed above the bottom. It weathers into the same angu- 

 lar patterns and has the same appearance in the hand specimen. Its thickness is from 8 to 15 

 feet. The overlying clays, as shown in this area, are yeUow and purple, and have frequent 

 lignitic bands but no coal, at least within the limits of the area covered by the map. 



I-K 10. CALIFORNIA AND SOUTHERN OREGON. 



The Upper Cretaceous (Chico formation) of California has long been known. 

 It was described by Diller and Stanton^**" as part of the " Shasta-Chico series." 

 (See J-K 10, Chapter XIV, p. 615.) Anderson ^ discussed its general relations. 

 Stanton ''^^^ has recently stated the following regarding the fauna: 



On the Pacific coast the Horsetown fauna is succeeded by the httoral Chico fauna, which is 

 distributed from the Yukon River to Lower California, occurring on the lower Yukon, the 

 Alaska Peninsula, Queen Charlotte and Vancouver islands, in middle and southern Oregon, 

 in the Sacramento Valley and the Coast Ranges of California to San Diego, and on the peninsula 

 of Lower California as far south as latitude 31° 30'. There are considerable local variations 

 in this fauna, as would be expected in view of its great range in latitude. The assemblage of 

 forms found on the Yukon is quite different from that occurring in the Sacramento Valley, and 

 still another facies is found in southern California, but these are all connected by common 

 species, so that there is no hesitation about referring both the northern and the southern facies 

 to the Chico fauna. The fauna as a whole, like the later Horsetown fauna, is Indo-Pacific 

 in its affinities and is strikingly different from the faunas of the Atlantic border and interior 

 regions of North America. Whiteaves and F. M. Anderson have argued for a connection during 

 Chico time between the Pacific and interior seas, but the evidence brought forward in support 



