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" An upper Miocene sedimentary succession, Melilla Basin, northeastern Morocco "
K. J. Cunningham
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Latin Dissertation
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English
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| Record Number
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1112983
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TLpq304204633
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| Main Entry
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K. J. Cunningham
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| Title & Author
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An upper Miocene sedimentary succession, Melilla Basin, northeastern Morocco\ K. J. Cunningham
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| College
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University of Kansas
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| Date
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1995
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1995
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| Degree
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Ph.D.
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| Page No
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371
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| Abstract
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In the Melilla basin of northeastern Morocco a Tortonian-to-Messinian sequence of sedimentary rocks, principally carbonates, has been studied in detail over an area of 30 usd\rm km\sp2.usd This succession includes a dramatically exposed shallow-marine carbonate complex. From bottom to top, the carbonate complex shows the following evolution: (1) a bryozoan red-algal limestone ramp; (2) a molluscan bioclastic limestone platform; (3) a dolomitized Porites fringing-reef complex; and (4) a dolomitized topography-draping series of peloidal grainstones, Porites reefs, and stromatolites, referred to as the terminal carbonate complex (TCC) by Esteban (1979). Overlying marginal and basinal rocks of the carbonate complex is a succession of mixed carbonate-siliciclastic sedimentary rocks, which reflect an upward transition from marine to continental deposition. Detailed section measuring, mapping of stratal geometries, of facies associations, and of depositional sequence boundaries on topographic maps and photomosaics has produced a detailed sequence stratigraphy and interpretative relative sea-level curve for the Melilla basin. The sequence stratigraphy and curve are anchored in time by a high-resolution chronostratigraphy resulting from new foraminiferal biostratigraphy, usd\rm\sp{40}Ar/\sp{39}Arusd dating of volcanic rocks, and magnetostratigraphy. The magnetic reversal stratigraphy of the Melilla basin has been correlated to the geomagnetic polarity time scale. Correlations have been independently corroborated with foraminiferal biostratigraphy and usd\rm\sp{40}Ar/\sp{39}Arusd dating of volcanic rocks. These correlations suggest the bryozoan red-algal ramp spans the Tortonian-Messinian boundary. Deposition of the fringing reefs began in chron C3An.2n and ended just after the onset of chron C3r (lower Gilbert). The overlying TCC and mixed carbonate and siliciclastic succession correlate within chron C3r. A usd\rm\sp{40}Ar/\sp{39}Arusd dated volcanic ash located near the marine to continental transition suggests marine conditions ended in the Melilla basin at about 5.75 Ma. This transition likely reflects final closure, during the Messinian "salinity crisis", of a seaway (Rifian corridor) that connected the southwestern Mediterranean Sea with the Atlantic Ocean. Results from the Melilla basin compared to data from other carbonate complexes of the Mediterranean region, a stable isotope record and cyclostratigraphy from northwestern Morocco, and global and regional eustatic curves has resulted in recognition of the complex interaction of eustacy, tectonics, and possibly climate as forcing mechanisms driving relative sea-level changes that influenced the development of carbonate depositional sequences in the Melilla basin. Results from this study can be applied to understanding the development of other upper Miocene carbonate depositional sequences and to the development of a global sea-level curve with greater than third-order resolution.
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carbonates
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Earth sciences
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Geology
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Messinian
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Tortonian
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