Early dolomitization of platform carbonates and the preservation of magnetic polarity

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doi: 10.1029/93JB00353
Author(s): McNeill, Donald F.; Kirschvink, Joseph L.
Author Affiliation(s): Primary:
Rosenstiel School of Marine and Atmospheric Science, Miami, FL, United States
Other:
California Institute of Technology, United States
Volume Title: Journal of Geophysical Research
Source: Journal of Geophysical Research, 98(B5), p.7977-7986. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0148-0227
Note: In English. Calif. Inst. Technol., Contrib. No. 5185. 48 refs.; illus. incl. sketch map
Summary: Results from a combination of techniques are presented to evaluate the nature of magnetization in shallow-water platform carbonates which have undergone recrystallization during early calcification and dolomitization. Magnetic grain separates, coercivity spectra, modified Lowrie-Fuller tests, magnetization efficiency, and magnetostratigraphic constraints indicate that the ultrafine-grained magnetite is preserved during early burial geochemical regimes, inversion from aragonite/high-magnesium calcite to low-magnesium calcite, and even pervasive dolomitization. These single-domain crystals are thought to occur as interacting multigrain clusters, some of which may exceed 1 µm in diameter. These large clusters may help prohibit magnetic reorientation during diagenesis. Furthermore, during both fabric preserving and fabric destructive dolomitization, the ultrafine-scale replacement process restricts reorientation of the clusters, thus preserving depositional or early postdeposition magnetic orientation. This early dolomitization (matrix stabilization) may even help protect and extend the subsurface lifespan of the original polarity. Copyright 1993 by the American Geophysical Union.
Year of Publication: 1993
Research Program: ODP Ocean Drilling Program
Key Words: 06 Petrology, Sedimentary; 07 Marine Geology and Oceanography; 24 Surficial Geology, Quaternary Geology; Absolute age; Atlantic Ocean; Bahamas; Carbonate platforms; Carbonate rocks; Carbonates; Carbonatization; Caribbean region; Cenozoic; Coercivity; Cores; Dates; Diagenesis; Dolomite; Dolomitization; Early diagenesis; Great Bahama Bank; Holocene; Limestone; Little Bahama Bank; Magnetic domains; Magnetic inclination; Magnetization; Marine sediments; Natural remanent magnetization; North American Atlantic; North Atlantic; Paleomagnetism; Quaternary; Recrystallization; Remanent magnetization; Sedimentary rocks; Sediments; Sr/Sr; TEM data; Textures; West Indies
Coordinates: N230000 N273000 W0750000 W0790000
Record ID: 1993019286
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