Review of Recent Geological Literature. 59 
land, which he thinks to have been quite probably continuous but with 
fluctuations in the extent and thickness of the ice, makes it wellnigh 
sure that the Chapelhall shells are like those observed in drift sections 
near Flamborough head by Mr. G. W. Lamplugh, occurring in frag- 
ments and shreds of marine beds eroded from a sea bottom over which 
the ice-sheet advanced upon the land. Sir Archibald Geikie also now 
regards the Chapelhall locality as insufficient to prove former marine 
submergence there. 
The Anorthosytes of the Minnesota Shore of Lake Superior. By 
Andrew C. Lawson. Bulletin No. 8, Geol. and Nat. Hist. Survey of 
Minnesota, 1893, pp. 1-23 ipart 1 1, with eight plates. Thegabbro forma- 
tion, whose outcrops on the lake Superior coast are the subject of this 
paper, reaches from Duluth north and east in a belt probably averaging 
20 miles wide to the vicinity of the Pigeon river on the international 
boundary. It is mostly separated from lake Superior by a similar 
width of the overlying Keweenawan series, beneath which its eroded 
surface has in some sections rounded, dome-shaped outlines, and occa- 
sionally rises boldly, as in Carlton peak, hundreds of feet above the ad- 
jacent only slightly tilted Keweenawan beds. This gabbro consists 
almost entirely of plagioclase feldspar, ranging in composition from 
labradarite to anorthite, for which class of rocks the name anorthosytes 
is used by Prof. Frank D. Adams in a memoir, very recently published, 
describing their occurrence in Canada.* The anorthosytes north of 
lake Superior were regarded by Irving as the lower part of his Kewee- 
nawan series, but Dr. Lawson shows thattheir pre-Keweenawan erosion 
and their contribution of boulders at many places to those overlying 
beds relegate the anorthosytes to an earlier period. Their coarsely crys- 
talline structure, furthermore, in connection with their well established 
igneous origin, points to the cooling and crystallization of this magma 
at a considerable depth, from which its overlying portions or higher beds 
of other rocks were removed by denudation as a land surface before 
the deposition of the Keweenawan. For this great formation of deep- 
seated igneous rock, which belongs to the class called batholites by 
Suess in analogy with the smaller intrusive laccolites of Gilbert, Dr. 
Lawson proposes the name Carltonian and tentatively correlates it with 
the Norian of the province of Quebec. Its age is regarded as Archean, 
and the time of its exposure by erosion is believed to be the great in- 
terval which everywhere appears to widely divide the Archean and 
Paleozoic eras. With this reference of the gabbro to so early time, the 
Keweenawan series north of lake Superior has probably a maximum 
thickness of no more than 2,000 feet, instead of the very much larger 
thickness which Irving claimed for it. 
The Laccolitic Sills of the Northwest Coast of Lake Superior. By 
Andrew C. Lawson. In pages 24 to 48, which form the second part 
of the foregoing bulletin, Dr. Lawson discusses the character and ori- 
gin of the trap sheets interbedded with the Animikie and Nipigon sed- 
Qeber das Norian oder Ober-Laurentian von Canada. Stuttgart, 1898. (Reviewed 
by Dr. A. ('. Lawson in Science, May 26. 1893.) 
