Lithostratigraphic and biostratigraphic evidence for brief and synchronous Early Mesozoic basalt eruption over the Maghreb (Northwest Africa)

Details Lithostratigraphic and biostratigraphic evidence for brief and synchronous Early Mesozoic basalt eruption over the Maghreb (Northwest Africa) Lithostratigraphic and biostratigraphic evidence for brief and synchronous Early Mesozoic basalt eruption over the Maghreb (Northwest Africa)

May 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm...s62a03e&link_type=abstract

American Geophysical Union, Spring Meeting 2001, abstract #S62A-03 INVITED

Mathematics

Logic

7205 Continental Crust (1242), 7220 Oceanic Crust, 8109 Continental Tectonics--Extensional (0905), 8121 Dynamics, Convection Currents And Mantle Plumes, 8450 Planetary Volcanism (5480)

Scientific paper

Previously very sparse biostratigraphic data suggested that the Early Mesozoic tholeiitic effusive and intrusive magmatism in the various basins of the Maghreb occurred over a long time (Ladinian-Hettangian). However, a detailed comparison of the stratigraphy underlying, interbedded with, and overlying the basalts in these basins shows not only remarkable similarities with each other, but also with sequences in the latest Triassic and earliest Jurassic of eastern North America. There, the sequences have been shown to be cyclical, controlled by Milankovitch-type climate cycles; the same seems to be true in at least part of the Maghreb. Thus, the Moroccan basins have cyclical sequences surrounding and interbedded with one or two basaltic units. In the Argana and Khemisset basins the Tr-J boundary is identified by palynology to be below the lowest basalt, and the remarkably close lithological similarity between the pre-basalt sequence in the other Moroccan basins and to the North American basins - especially the Fundy basin - suggests a tight correlation in time. Likewise, the strata above the lowest basalt in Morocco show a similar pattern to what is seen above the lowest basalt formation in eastern North America, as do the overlying sequences. Furthermore, geochemistry on basalts in the Argana, Bou Fekrane, Khemisset, and Iouawen basins indicate they are high-Ti quartz-normative tholeiites as are the Orange Mountain Basalt (Fundy basin) and the North Mountain Basalt (Newark basin). The remarkable lithostratigraphic similarity across the Maghreb of these strata suggest contemporaneous and synchronous eruption over a time span of less than 200 ky, based on Milankovitch calibration, and within a ~20 ky interval after the Triassic-Jurassic boundary. Differences with previous interpretations of the biostratigraphy can be rationalized as a result of: 1, an over-reliance on comparisons with northern European palynology; 2, over-interpretation of poorly preserved fossils; and 3, rarity of early Jurassic non-marine ostracode assemblages.

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