Environmental changes at the Frasnian-Famennian boundary in Central Morocco (Northern Gondwana): integrated rock-magnetic and geochemical studies - Archive ouverte HAL Accéder directement au contenu
Chapitre D'ouvrage Année : 2007

Environmental changes at the Frasnian-Famennian boundary in Central Morocco (Northern Gondwana): integrated rock-magnetic and geochemical studies

Résumé

Rock magnetic (magnetic susceptibility and hysteresis parameters) and geochemical analyses (major and trace elements) were carried out on whole rock samples of two Frasnian–Famennian boundary sections, Anajdam and Bou-Ounebdou in the Central Morocco (Western Meseta). During the Frasnian, the decreasing trend of the magnetic susceptibility signal, mainly carried by low-coercivity magnetite grains, indicates a gradual reduction of detrital influx. This decrease in detrital input parallels a Frasnian long-term sea-level rise. In the Late Frasnian Kellwasser Horizons, that are classically considered to represent highstand deposits, the magnetic signal exhibits the lowest intensities in connection with maximum diamagnetic contribution of the carbonate fraction. With respect to geochemical data, the two black carbonate-rich Kellwasser Horizons are characterized by noticeable positive anomalies of bottom-water dysoxic proxies and of marine primary productivity markers. Our data thus suggest that in Central Morocco, the Late Frasnian marine environments were marked by a relatively important biogenic productivity favouring the onset of oxygen-depleted conditions during periods of maximum transgression on the continental platforms.
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hal-00523941 , version 1 (13-09-2022)

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Paternité - Pas d'utilisation commerciale

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Laurent Riquier, Olivier Averbuch, Nicolas Tribovillard, Abderrazak El Albani, N. Lazreq, et al.. Environmental changes at the Frasnian-Famennian boundary in Central Morocco (Northern Gondwana): integrated rock-magnetic and geochemical studies. R.T. Becker & W.T. Kirchgasser. Devonian Events and Correlations, Geological Society - Special Publication 278, pp.197-217, 2007, ⟨10.1144/SP278.9⟩. ⟨hal-00523941⟩
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