Steep-sided carbonate mud mounds in the Middle Devonian of the eastern Anti-Atlas, Morocco

Article Abstract:

Middle Devonian carbonate mud mounds are exposed along the northern margin of the Sahara Craton in the eastern Anti-Atlas mountain range of Morocco. These rocks have not been exposed to metamorphic pressures and their current structures are identical with their original distributions. Sponge and coral fossils are rare from these deposits in contrast with nearby contemporaneous deposits. These mounds probably formed on a gentle gradient into a shallow basin. The distribution of organisms in these mounds suggests a transition to a pelagic platform not far from the deepest mound.

Basins (Geology), Sedimentary structures

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Geochemistry of bimodal amphibolitic-felsic gneiss complexes from eastern Massif Central, France

Article Abstract:

The Middle Allochthonous Unit of the eastern and southern French Massif Central is dotted with bimodal amphibolitic-felsic gneiss complexes containing high-grade basic and acidic meta-igneous rocks. Chemically diverse metabasites from two gneiss complexes in the unit is an indication that the complexes have different mantle sources. The bimodal association between the metabasites suggest a transition period between continental rifting and oceanic crust formation during the spreading event that occurred during the Cambro-Ordovician.

France, Rocks, Igneous, Igneous rocks, Gneiss

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Hydrothermal origin of Devonian conical mounds (kess-kess) of Hamar Lakhdad Ridge, Anti-Atlas, Morocco: comment and reply

Article Abstract:

D. Mounji et al provided carbon and oxygen as well as strontium isotope data for microspars and diagenetic cements of Lower Devonian mud mounds from Morocco. Based on low delta(super 18)O values of the microspars, they suggested that the precipitation of the carbonate muds and the formation of the mud mounds was caused by hydrothermal venting. While hydrothermal venting may offer a novel approach for explaining the formation of the Lower Devonian mud mounds, the isotope evidence given by Mounji et al do agree with the conclusion.

Hydrothermal vents

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