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Trilobites from the latest Frasnian Kellwasser crisis in North Africa [Mrirt, Central Moroccan Meseta]

100%

Feist R.

Acta Palaeontologica Polonica

2002

tom 47

nr 2

Latest Frasnian trilobites are recorded for the first time from North Africa. They occur in oxygenated limestones between the Lower and Upper Kellwasser horizons at Bou Ounabdou near Mrirt, central Moroccan Meseta. The faunas are very close to the contemporaneous associations in European sections both by their taxonomic composition and by patterns of evolutionary behavior towards eye reduction. Two new taxa are described: Gondwanaspis mrirtensis gen. et sp. nov., which is the last known representative of the Odontopleuridae before its extinction at the base of the Upper Kellwasser horizon, and Pteroparia ziegleri maroccanica subsp. nov., a geographical variant of the nominal subspecies from Sessacker in the Rhenish Slate Mountains.

The Frasnian-Famennian events in a deep-shelf succession, Subpolar Urals: biotic, depositional, and geochemical records

80%

Yudina A. B., Racki G., Savage N. M., Racka M., Malkowski K.

Acta Palaeontologica Polonica

2002

tom 47

nr 2

The Frasnian–Famennian (F–F) boundary is well biostratigraphically documented in the Palmatolepis−rich deposits exposed along the Syv’yu River in the lower slopes of the Subpolar Urals. The thin−bedded calcareous−clayey−siliceous deep−slope succession of the Vorota Formation appears to represent continuous Domanic−type deposition throughout the world−wide carbonate crisis time, without evidence for the basal Famennian hiatus or a large−scale sedimentary perturbation within a regressive setting. The northernmost Laurussian sequence exhibits many well known signatures throughout the broad F–F timespan: the appearance of organicand clay−rich deposits, icriodontid and radiolarian blooms, and a correlative shift of several geochemical proxies towards hypoxic and high−productivity regimes, perfectly recorded by positive 13Ccarb excursions of +3.5‰. Integrative biotic, microfacies and geochemical data substantiate a longer−term oceanographic destabilization, attributable to multiple Earth−bound triggering factors in (episodically enhanced?) greenhouse climate and punctuated eustatic sea−level highstands, superimposed on the elevated deposition of organic carbon−rich sediments during the Upper Kellwasser Event. Unsteady eutrophicated, and oxygen−depleted ecosystems during the F–F biotic crisis interval could be assumed, especially when intensified by various spasmodic tectono−volcanic phenomena in the incipiently closing Ural Ocean.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

1 Feist R.

1 Malkowski K.

1 Racka M.

1 Racki G.

1 Savage N. M.

1 Yudina A. B.

2 2002

Wyniki wyszukiwania

Trilobites from the latest Frasnian Kellwasser crisis in North Africa [Mrirt, Central Moroccan Meseta]

The Frasnian-Famennian events in a deep-shelf succession, Subpolar Urals: biotic, depositional, and geochemical records