REVIEWS 583 
The Younger Rock-Series of New Zealand. By P. MARSHALL, 
R. Speicut, and C. A. Corron. Trans. N.Z. Inst., XLITI, 
(1910), 378-407; figs. 9; pl. 1. 
Several geologists have described various unconformities in this 
thick series, yet no two have put them in the same stratigraphical 
position. Such discrepancies interested the writers to make detailed 
examinations of these ‘“‘unconformities,” the evidences for which they 
were unable to find. Correlation with European faunas places the 
lowermost of the series in the Cretaceous, the prominent limestones in 
the Oligocene, and the uppermost beds in the Pliocene. 
Ane ok. 
A Geologic Reconnaissance in Southeastern Seward Peninsula and 
the Norton Bay-Nulato Region, Alaska. By PuHILip S. SMITH 
and H. M. Eakin. Bull. 449, U.S. Geol. Survey, rort. 
Ppa t4o: figs. 15 pls, 13. 
The Norton Bay-Nulato region lies to the east of the southeastern 
portion of Seward Peninsula. Both areas were little known before this 
reconnaissance, for they are unimportant in connection with mining. 
The Nulato-Norton Bay area is largely one of Cretaceous sediments, 
and the southeastern portion of Seward Peninsula is part of the inclosing 
rim of older formations. Pre-Silurian formations are present in a highly 
metamorphosed condition. Less metamorphosed and lying uncon- 
formably upon the earlier are Silurian-Devonian-Carboniferous (?) 
strata. Intrusions and extrusions followed, accompanied by mountain- 
building and extensive erosion. Cretaceous formations overlie uncon- 
formably the preceding rocks, and since their deposition the region has 
again been subjected to diastrophism of mountain-building intensity. 
Intrusions followed, and later still extrusions, some of which are rather 
recent. 
Gold placers are very local, and are only in the regions of metamor- 
phic rocks. Gold lode mining has been attempted only in a few places, 
and has never gone beyond the prospecting stage. Some silver-lead 
mining had been done to the extent of a few hundred tons of ore. Pros- 
pecting for copper has been without success commercially. In the area 
of Cretaceous sediments coal is generally present, but too thin or too 
crushed to be of any value. 
AG Ey He 
