CORRELATION OF GRAVITY ANOMALIES WITH THE KEWEENAWAN GEOLOGY OF WISCONSIN AND MINNESOTA

Abstract

Listen

Translate article

Research Article| August 01, 1956 CORRELATION OF GRAVITY ANOMALIES WITH THE KEWEENAWAN GEOLOGY OF WISCONSIN AND MINNESOTA EDWARD THIEL EDWARD THIEL UNIVERSITY OF UTAH, SALT LAKE CITY, UTAH Search for other works by this author on: GSW Google Scholar Author and Article Information EDWARD THIEL UNIVERSITY OF UTAH, SALT LAKE CITY, UTAH Publisher: Geological Society of America Received: 21 Jun 1955 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright 1956, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1956) 67 (8): 1079–1100. https://doi.org/10.1130/0016-7606(1956)67[1079:COGAWT]2.0.CO;2 Article history Received: 21 Jun 1955 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation EDWARD THIEL; CORRELATION OF GRAVITY ANOMALIES WITH THE KEWEENAWAN GEOLOGY OF WISCONSIN AND MINNESOTA. GSA Bulletin 1956;; 67 (8): 1079–1100. doi: https://doi.org/10.1130/0016-7606(1956)67[1079:COGAWT]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Gravitational mapping by the University of Wisconsin has delineated what appears to be the largest positive-anomaly feature on the North American continent, extending from the Lake Superior region southwest into Kansas. For the greater part of its length this midcontinent gravity high is flanked on both sides by gravity lows. Because the southern part of the anomalous area is blanketed by Paleozoic sediments, the cause of the anomaly was sought first at its northern end, around Lake Superior, where Precambrian rocks crop out to facilitate a correlation of gravity and geology.Around western Lake Superior the positive anomalies correlate with Keweenawan lava and gabbro. The negative anomaly on the Bayfield Peninsula reflects a thick accumulation of sandstone and shale which was deposited in the subsiding Lake Superior syncline during Upper Keweenawan time. A second thick accumulation of sedimentary rocks may underlie the gravity low at Cumberland. Steep gravity gradients indicate the Douglas fault. A second major fault symmetric to the Douglas fault is mapped in northwestern Wisconsin on the opposite side of the Lake Superior syncline. The center of the syncline has been thrust upward between the two faults as a horst. A traverse along the spit at Duluth fails to detect the North Shore fault as it is usually mapped; if the fault exists, no great amount of sandstone is placed in juxtaposition to basaltic lava. Detailed correlation of gravity and geology is presented on maps and structure sections along lines of gravity traverse.The usual isostatic correction cannot reduce the gravity differentials around western Lake Superior. A geological correction which allows for the effects of near-surface geology does account for most of the anomalies. Any attempt to compute the extent of crustal warping at depth without allowing for the near-surface geology would have led to considerable error. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.