| 释义 |
Keweenawan, a.|kiːwiːˈnɔːən|
Also † Keweenawian.
[f. the name of Keweenaw Peninsula, Michigan + -an, -ian.]
Of, pertaining to, or designating the most recent division of the Proterozoic in North America, as represented by rocks in the region of the Great Lakes. Also absol., the Keweenawan period or rocks.
1876T. B. Brooks in Amer. Jrnl. Sci. CXI. 210 We are therefore justified, I think, in regarding the Copper⁓bearing rocks of Lake Superior as a distinct and independent series, marking a definite geological period which separates the Silurian from the Huronian ages... Since Keweenaw Peninsula forms one of the most striking geographical features in Lake Superior.., I suggest the name Keweenawian for this period. 1883R. D. Irving Copper-Bearing Rocks Lake Superior ii. 25 The Keweenawan rocks form the larger part of Keweenaw Point. 1893Jrnl. Geol. I. 126 The source of the lavas of the Keweenawan. 1930Econ. Geol. XXV. 252 Erosion had peneplained the original folds of the Keewatin and Timiskaming rocks before Keweenawan time. Ibid. 262 They are distinctly younger than the Algoman and older than the Keweenawan. 1935Bull. Geol. Soc. Amer. XLVI. 504 The Keweenawan lavas of the Lake Superior district form the inner border of the Lake Superior syncline. They crop out over an area of several thousand square miles, and in one section on Keweenaw Point, Michigan, form a series with a minimum thickness of 15,000 feet. 1970Dorr & Eschman Geol. Michigan iv. 56/1 Keweenawan lavas were derived from molten magmas of the ‘basic’ or ferro-magnesian type. |