SCIENCE. 



[Vol. XXI. No. 538 



placing or absorbing it, is it not likely that such an event has 

 occurred frequently and in many different parts of the earth's 

 crust? Geological records are, indeed, full of suggestions that 

 such is the case. Yet in all our current discussions of orogeny, 

 epeirogeny, and regional metamorphism, how little is this factor 

 in the problem considered? What part has the development of 

 the Nova Scotia batholite played in the folding of the Cambrian 

 strata of that province, in their metamorphism and in their be- 

 coming charged with gold ? What part has the development of 

 the great batholite of the Sierra Nevada played in the folding and 

 metamorphism of the earlier Mesozoic rocks of California and in 

 their becoming charged with gold? What part has the develop- 

 ment of the great British Columbian batholite played in the fold- 

 ing and metamorphism of the earlier Mesozoic strata of the west 

 coast of that province? Was the British Columbian batholite 

 synchronous in its development with the Sierra Nevada batholite? 

 Are they separate and distinct affairs, or are they simply geo- 

 graphically separate manifestations of one stupendous process of 

 crust development? In either case has not the exposure by de- 

 nudation of these great batholites and their intrusive relations to 

 the surrounding terranes practically reproduced the conditions 

 which we find in the Archaean terranes of the Canadian plateau? 

 These are a few of the questions which can only be profitably 

 discussed when the batholite is recognized as a much larger ele- 

 ment in tectonic geology than the dyke, the neck, the boss, the 

 sill, or the laccolite. Batholites abound. Why should they not 

 be recognized ? 



2. A second important result is the immense simplification 

 which is effected in Archaean geology in the Canadian territory, 

 where most questions of that ilk must find their final solution. 

 Hitherto the Norian rocks have been classed as part of a supposed 

 system of metamorphic sedimentary strata known as the Lauren- 

 tian This system was divided by Logan into an upper and a lower 

 division, the latter being sub-divided into two parts, viz. : the 

 Grenville series and the Ottawa gneiss, so that his scheme stood 

 thus : — 



Norian series = 



Grenville series = Upper division 



Ottawa gneiss = Lower division 



Upper Laurentian 

 of Lower Laurention. 



The recognition of the irruptive character and post-Gren- 

 ville age of the Norian rocks is a great gain, and reduces 

 the Laurentian system to two members. The simplification 

 thus effected suggests to the present writer still other possi- 

 bilities in the same direction. It seems probable that the Gren- 

 ville is a profoundly metamorphosed series of sedimentary 

 strata. Its bedded character and the fact of its being com- 

 posed of strata of limestone, quartzite, iron ore, graphite, etc., 

 in addition to the gneisses, favor this view. The Ottawa gneiss, 

 on the other hand, has a very different character. There are no 

 beds of limestone, or quartzite, or iron ore, or graphite. The 

 mass of the formation is eminently granite, with gneissic folia- 

 tion, which in some oases is well defined, and in others vague or 

 almost absent. What is the relation of the Ottawa gneiss to the 

 Grenville series ? The former would be recognized by any pe- 

 trographer as a granite — a plutonic igneous rock. Professor 

 Adams recognizes the geological identity of the Ottawa gneiss 

 with the Laurentian gneiss and granite which the writer has de- 

 scribed as invading the upper division of the Archaean complex 

 (Ontarian system) in the region northwest of Lake Superior. 

 There the igneous irruptive and batholitic character of the granites 

 and gneisses (= Ottawa gneiss) and its invasion of the Upper 

 Archaean rocks is unequivocally demonstrated by evidence which 

 has been abundantly adduced elsewhere. Does the Ottawa gneiss 

 of the Ottawa valley bear a similar batholitic and intrusive rela- 

 tion to the Grenville series? From what the writer knows of the 

 region, it seems to him eminently probable that such will be 

 found to be the case. This hypothesis is favored somewhat by 

 certain harmonious analogies which it would establish between 

 the Archeean complex in the Lake Superior region and the region 

 of the Lower Ottawa. Generally, the Archaean complex through- 

 out Canada, omitting the Norian, is composed of two great divi- 

 sions. The lower division seems generally to have the petro- 



grapbical characters of the Ottawa gneiss. The upper division 

 is usually recognizable as an assemblage of metamorphic, sedi- 

 mentary, or mixed sedimentary and volcanic strata. Part of this 

 upper division has usually been referred to as Huronian, but, ac- 

 cording to several authorities, this term was originally applied to 

 a post- Archaean series on the north shore of Lake Huron; and 

 there is some confusion attending its use. Even when applied to 

 Archaean rocks, the term has embraced only a portion of the 

 upper division of the complex. In western Ontario, this upper 

 division includes at least one other group besides that which has 

 usually been called Huronian. The writer has elsewhere pro- 

 posed the term " Ontarian system," as a comprehensive designa- 

 tion to embrace the whole of the upper division of the Archaean 

 in western Ontario, Now it seems to the writer that the Gren- 

 ville series in Quebec occupies the same stratigraphical position in 

 the Archaean complex as does the Ontarian system (embracing 

 Contchiching and Keewatin [Huronian?]) in western Ontario. 

 Admitting, for the sake of clearly stating the hypothesis, that the 

 Grenville series is the equivalent; of Ontarian system, or any part 

 of it, we would have the following parallelism: — 



1 See Bulletin, No. 8, Geolog. and Nat. Hist. Surv. of Minnesota. 



If this hypothetical correlation should ever be established, it 

 would then seem that different names and different stratigraphi- 

 cal positions had been given to groups of strata geologically 

 equivalent because of their petrographical dissimilarity. The 

 Grenville series is characterized by limestones and quartzites, with 

 little or no volcanic admixture. In the Ontarian system of 

 western Ontario sedimentary rocks, in a more or less metamorphic 

 state, are common enough; but there is a scarcity of crystalline 

 limestones and quartzites, and altered forms of volcanic rocks 

 abound. This petrographical dissimilarity, however, in no way 

 militates against their geological correlation. It is interesting to 

 note in this connection that the Hastings series, which is geo- 

 graphically between the Quebec region and the Lake Superior 

 region, is intermediate in petrographical character between its 

 suggested equivalents on either side. By some authors it has 

 been correlated with the Grenville series, and by others with the 

 Huronian (Archaean). 



GEOLOGY OF TUCUMCARI, NEW MEXICO. 



BT W. F. CUMMINS, TEXAS GEOLOGICAL SURVEY, AUSTIN, TEXAS. 



In 1852, Professor Jules Marcou, as United Slates geologist, 

 made a trip across the country with the engineers who were sent 

 out to survey a railroad route from Fort Smith, Ark., to the 

 Pacific Ocean, near the thirty-second parallel. On that trip he 

 passed through the Tucumcari region, and published a description 

 and section of Pyramid Mountain, one of the representative 



