« PrejšnjaNaprej »
Cairnes's key is as follows: The strip along the international boundary is divided into blocks comprising 10 minutes of latitude and approximately 10 minutes of longitude, which are numbered from north to south with roman numerals. Each main block is subdi
. vided into units approximately one-fourth of a mile square, designated from south to north by the numbers 1 to 46 and from west to east by the letters a to t. The main blocks falling within this area and the method of designating their subdivisions are indicated in Figure 3.
On the assumption that this scheme was used consistently and that no typographic errors are present in the numbers of the fossil collections given in Cairnes's memoir and after making the best possible adjustment of some of the obvious inconsistencies, the following lots of Cairnes's fossils are interpreted by the writer as having been collected from the essentially noncalcareous rocks, ranging in age from Ordovician to Carboniferous. XX i 25:
Dicranograptus cf. D. ramosus (Hall).
Harpes? sp. The three graptolites listed above were determined by R. Ruedemann to be of Lower Ordovician age, or, more specifically, equivalent to the Normanskill, the upper part of which, however, Ruedemann considers to be of early Black River (Lowville) age, which is commonly classified as Middle Ordovician. The other invertebrates
XV a b 35:
Cladopora cf. C. dichotoma Hall.
This collection, determined by E. M. Kindle as Devonian but possibly different from the type Middle Devonian fauna, was obtained, according to the scheme of locations given in Figure 3, about 27, miles west of the boundary and an equal distance south of the Kandik River, in an area believed to be composed essentially of Lower Cretaceous rocks. If no error in placement has been made, these fossils probably came from essentially noncalcareous Devonian rocks infolded into the Cretaceous.
L. D. Burling, who accompanied the boundary party in 1912, also made several Ordovician collections along the boundary north of the Yukon. These have been studied by R. Ruedemann, and the results of his study are given in the identifications below tabulated :
Cactograptus n. sp.
Callograptus cf. C. diffusus Hall. 4662:
Lingula n. sp.
Didymograptus cf. D. extensus Hall. 4680:
Caryocaris n. sp.
Didymograptus extensus Hall. 4683:
Lingula n. sp.
Didymograptus nitidus Hall.
In a collection of lower Ordovician praptolites from the Alaska-Yukon boundary sent to the writer by L. D. Burling, of the Geological Survey of Canada, for identification, a small number of specimens of Caryocaris were noted, one of which retains the abdomen in place. This fact as well as the presence of other characters hitherto unknown have suggested this note, the material having been kindly presented to the New York State Museum by Mr. Burling. The Alaska-Yukon material is not obscured by an imperfect cleavage and leaves no doubt that the posterior margin of the carapace was indeed furnished with a fine comb of uniform bristles or teeth corresponding to the "fringe" observed in certain species of Ceratiocaris.
In 1928 P. S. Smith made a collection of Lower Ordovician graptolites from a bed just above the Upper Cambrian limestone, at the
* Ruedemann, R., Note on Caryocaris salter: New York State Mus. Bull., Nos. 227–228, pp. 97-98, 1919.
head of the North Fork of Shade Creek, which were determined by Edwin Kirk, of the United States Geological Survey, as Diplograptus sp. and assigned by him to the Normanskill. The exact locality (28AMt261) is 1 mile N. 171/2° W. from “ Hug” boundary triangulation station (McCann Hill). These fossils come from a narrow band of slate, directly above the Upper Cambrian limestone but directly below a group of rocks composed of argillite and chert, of Middle Devonian age. This Ordovician slate is too small to show on the scale of the accompanying map but can be discriminated and mapped on a larger scale. The occurrence is here recorded, for the benefit of later workers in this area.
Most of the Carboniferous fossils collected by Cairnes occurred in rocks that were dominantly noncalcareous, although some of the upper Mississippian rocks evidently contain thin beds of limestone, as they do at Calico Bluff, on the Yukon. The Carboniferous fossils of the boundary were studied originally by G. H. Girty, of the United States Geological Survey, and those collected from latitude 66° southward to the Yukon have recently been reexamined by him. Three of these collections from the vicinity of Ettrain Creek, which occur in limestone and are now referred by Girty to the Permian, are separately listed under the Tahkandit (Permian) limestone. (See p. 129.) All the others, as revised, are listed below:
XIV s 43:
Martinia ? sp.
Cleiothyridina cf. C. pectenifera.
Marginifera? cf. M. involuta.
Lithostrotion ? sp.
Productus cf. P. curvirostris.
Camarophoria cf. C. explanata XVII ; 30:
Chonetes cf. C. variolatus.
Spirifer cf. S. nikitini.
Chonetes cf. C. variolatus.
XIX c d 30, 31, 32:
Chonetes cf. C. ostiolatus.
Camarotoechia sp. Girty's latest statement regarding the probable age and correlation of the fauna above listed is given herewith:
I find it possible to repeat at this time most of what I wrote to Mr. Cairnes in 1912—something that does not always happen. As regards the age of this