APPENDIX D. GEOLOGY. 145 



From the 3d of May to June 2d, the formation passed over is, as I 

 judge from Dr. Shumard's sections and descriptions, the predominant 

 one along the upper part of Red river. All the appended sections of 

 Dr. Shumard, except Nos. VI and XI, exhibit the characters and varie- 

 ties of this deposite. Red clay is the most striking and abundant mem- 

 ber ; and above this we have a yellow or lighter colored sandstone, often 

 finely laminated. As subordinate members, we have blue and yellow 

 clay, gypsum, non-fossiliferous limestone, conglomerate, and copper 

 ore. Overlying these strata is what Dr. Shumard calls " drift," which 

 is surmounted by soil. Excepting the gypsum and the copper, no speci- 

 men of this formation was put into my hands ; and only one petrefao- 

 tion which is a coral from the base of section No. IV, unless the fossil- 

 wood belongs to it. 



Now the question is, shall we regard this formation as tertiary, or 

 cretaceous ? With the means in my hands I feel unable to decide this 

 question. If I am right in referring the fossil coral found in it to the 

 genus Scyphia, as described by Goldfuss, (Petrefacta Germanise, Tab. 

 XXXII, fig. 8,) it most probably belongs to the cretaceous period ; for, 

 of the one hundred and twenty species of this genus enumerated in 

 Bronn's Index Paleontologicus, only one is found above the chalk. As 

 to the fossil-wood, which I shall notice more particularly further on, it 

 is well known to occur in almost all the fossiliferous deposites. Upon 

 the whole, I rather lean to the opinion that these strata may belong to 

 the cretaceous formation ; though it is singular, if such be the case, that 

 the fossil remains are so scarce, since, as we shall see, they occur abun- 

 dantly in another portion of the field in which the cretaceous rocks 

 abound. 



Under these circumstances I shall speak of this deposite under the 

 name of the Red Clay Formation, save where gypsum is very abundant, 

 and then I call it the Gypsum Formation ; and thus have I marked 

 these rocks on your map. 



The sandstone which constitutes the upper part of this formation has 

 a slight dip, in a few places, of 2° or 3°. On the 8th of June, however, 

 a grayish yellow sandstone is described as having a westerly dip of 40°; 

 and on the 9th of June, " an outcrop of finely laminated, red, ferruginous 

 sandstone" is mentioned, having an irregular northeasterly dip of 30°, as 

 shown on section VI. The next day the strata were found standing 

 nearly perpendicular ; but whether this sandstone is the same as that 

 lying above the red clay, is not mentioned. If it is, its great dip proba- 

 bly results from some local disturbance. If it is not, it is probably a 

 protruding mass of older rock exposed by denudation or upheaval. 

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