Magnetic fabrics in Quaternary sediments, Ursa Basin, northern Gulf of Mexico record transport processes, compaction and submarine slumping

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doi: 10.1016/j.margeo.2011.05.007
Author(s): Meissl, Sandra; Behrmann, Jan H.; Franke, Christine
Author Affiliation(s): Primary:
IFM-GEOMAR, Kiel, Germany
Other:
University of Bremen, Germany
Volume Title: Marine Geology
Source: Marine Geology, 286(1-4), p.51-64. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0025-3227 CODEN: MAGEA6
Note: In English. 45 refs.; illus., incl. sect., 1 table, sketch map
Summary: The continental slope of the northern Gulf of Mexico seaward of the Mississippi Delta is characterized by very rapid Quaternary sedimentation. Thick sequences of underconsolidated muds and mudstones are present, which are severely overpressured. In the Ursa Basin, Site U1322 of the Integrated Ocean Drilling Program (IODP) provided an excellent coring record of interleaved fine-grained turbidites and hemipelagic sediments, in part severely affected by submarine slumping and sliding after deposition. Cores were continuously sampled and analyzed for anisotropy of magnetic susceptibility (AMS), to elucidate the effects of different transport mechanisms and degree of settling and consolidation on magnetic fabric properties. Generally AMS ellipticity increases with depth irrespective of transport mode, due to loss of porosity. Samples from slumped mass transport deposits (MTD), however, have higher AMS if compared to immediately overlying non-slumped material. MTD samples dominantly show triaxial magnetic fabrics whereas those found in non-slumped sediments are much more oblate. Long axes of the fabric ellipsoid reflect the direction of eastward to southward suspension transport in samples not overprinted by sliding or slumping. Short ellipsoid axes in non-slumped material are vertical, and thus parallel to the axis of maximum uniaxial shortening. In the MTD samples, many short ellipsoid axes are inclined, reflecting an overprint of the uniaxial shortening by bed-parallel shearing induced by the slumping. Shear and MTD transport direction deduced from the fabrics is top-to-SE, downslope along the morphological axis of Ursa Basin. Generally we show that magnetic fabrics of muds and mudstones are sensitive recorders of sedimentary and tectonic processes, and can be used to reconstruct essential parts of basin history. Abstract Copyright (2011) Elsevier, B.V.
Year of Publication: 2011
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 06 Petrology, Sedimentary; Anisotropy; Atlantic Ocean; Boreholes; Cenozoic; Compaction; Continental margin sedimentation; Continental slope; Cores; Expedition 308; Fabric; Foliation; Gulf of Mexico; IODP Site U1322; Integrated Ocean Drilling Program; Lithostratigraphy; Magnetic fabric; Magnetic properties; Magnetic susceptibility; Magnetostratigraphy; Marine sediments; Mass movements; North Atlantic; Northern Gulf of Mexico; Paleomagnetism; Porosity; Quaternary; Sedimentation; Sediments; Shear strength; Slumping; Ursa Basin
Coordinates: N280600 N280600 W0890100 W0890200
Record ID: 2011087848
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands