Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Origin of the odd-twins anomaly; magnetic effect of a unique stratigraphic marker in the Appalachian foreland basin, Gulf of St. Lawrence

John W. F. Waldron, Jerry DeWolfe, Robert Courtney and Doris Fox
Origin of the odd-twins anomaly; magnetic effect of a unique stratigraphic marker in the Appalachian foreland basin, Gulf of St. Lawrence
Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre (November 2002) 39 (11): 1675-1687

Abstract

The "Odd-twins magnetic anomaly" is a pair of linear asymmetric positive anomalies located in the Gulf of St. Lawrence, over the post-Taconian, pre-Acadian foreland basin fill related to the development of the Appalachians. A marine magnetic survey allowed the anomaly to be traced close to the coast of Newfoundland, and an on-land survey identified both peaks within the area of outcrop of the Late Ordovician Long Point Group. Sandstones of high susceptibility sampled from sparse outcrops close to the locations of the anomaly peaks contain up to 0.58% magnetite. Models involving dipping sheets of sandstone having similar and slightly higher susceptibility can explain both the onshore and offshore anomaly. The magnetite is of detrital origin and represents a paleoplacer heavy mineral concentration formed in a marginal marine environment. The anomaly provides a unique tie point between the known onshore stratigraphy and the succession in the foreland basin, known only from industry seismic profiles. This tie point indicates that nearly half of the recorded subsidence of the post-Taconian foreland basin took place in the Late Ordovician, suggesting that a major event within the Appalachian orogen loaded the Laurentian margin at this time. A subsequent hiatus, representing the Early Silurian, may record thermal uplift associated with the Salinian orogeny. Renewed Late Silurian to Devonian loading and sedimentation resulted from the Acadian orogeny.


ISSN: 0008-4077
EISSN: 1480-3313
Coden: CJESAP
Serial Title: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre
Serial Volume: 39
Serial Issue: 11
Title: Origin of the odd-twins anomaly; magnetic effect of a unique stratigraphic marker in the Appalachian foreland basin, Gulf of St. Lawrence
Affiliation: University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada
Pages: 1675-1687
Published: 200211
Text Language: English
Summary Language: French
Publisher: National Research Council of Canada, Ottawa, ON, Canada
References: 37
Accession Number: 2003-024284
Categories: StratigraphyApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sect., strat. col., geol. sketch map
N48°30'00" - N49°00'00", W59°15'00" - W58°45'00"
Secondary Affiliation: Saint Mary's University, CAN, CanadaGeological Survey of Canada, CAN, Canada
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200309
Close Modal

or Create an Account

Close Modal
Close Modal