Clay Mineralogy of Cretaceous and Cenozoic Sediments off the Moroccan Margin, Deep Sea Drilling Project Sites 415 and 416

Abstract

The Upper Jurassic to Pleistocene, mainly turbiditic sediments recovered at Sites 415 and 416 on the Moroccan margin contain diversified and variegated clay assemblages. Most of the clay species and associated non-clay minerals are considered to be detrital materials, including smectite, fibrous clays, and perhaps part of the zeolite (clinoptilolite) and cristobalite. The Tithonian and Lower Cretaceous turbidites are chiefly marked by the presence of micaceous and chloritic minerals, resulting from tectonic rejuvenations during the oceanic widening. Minor variations in the abundance of illite, kaolinite, and mixed-layer clays could have been caused by climatic variations. Most of the Upper Cretaceous and Paleogene sediments contain abundant well-crystallized smectite, mainly inherited from continental soils developed in poorly drained areas. This suggests that the climate was hot, with strong variations in seasonal humidity. Fibrous clays developed during two periods, attapulgite (= palygorskite) during the early Aptian, attapulgite and sepiolite during the early Eocene. Both minerals indicate the existence of hot and seasonally humid climates which changed northward and southward. Their occurrence or increase in abundance shows the existence of marginal, closed to semi-closed basins in which they formed in confined chemical conditions and were reworked as a result of the margin instability. During the late Cenozoic, the increase of primary minerals and the reappearance of mixed-layer clays and associated non-clay minerals reflect a progressive and irregular worldwide cooling, unfavorable for establishment of soils and favoring direct erosion of rocks and the development of oceanic currents. This change chiefly began in the late Miocene, but it began earlier off Morocco than off southern Europe, suggesting an arid trend along northwest Africa as long ago as the Oligocene.

Geochemical investigation of the taphonomy, stratigraphy, and palaeoecology of the mammals from the Ouled Abdoun Basin (Paleocene-Eocene of Morocco)

“…The presence of early diagenetic dolomite and gypsum in some of these deposits were also interpreted as a consequence of an arid climate during the Ypresian, and only a low amount of seasonal precipitation was proposed (e.g., Mohr, 1986;Fechner, 1988). In addition, the rarity of detritic (clastic) material in the phosphate basins (Lucas and Prevôt-Lucas, 1995), and the high quantity of palygorskite clay mineral in the Paleogene deposits in the Atlas (Daoudi, 2004;Knidiri et al, 2014) and offshore Morocco (e.g., Chamley et al, 1980), would further suggest a dry semi-arid late Paleocene -Ypresian climate in the region. By contrast, Herbig and Gregor (1990) have advocated a tropical humid climate based on the discovery of mangrove macro-plant remains of Nypa palms from Thanetian-Ypresian levels in the Ouarzazate Basin, based on a re-evaluation of early available data.…”

Mineralogical and Geochemical Investigations of Sediments on the Mazagan Plateau, Northwestern African Margin (Leg 79, Deep Sea Drilling Project)

“…These mineralogical similarities suggest a comparable origin for the different species in both sites. A predominantly detrital origin for the clay assemblages is interpreted based on previous studies on the Moroccan margin and in the whole North Atlantic Basin (Mélières, 1978); Chamley, 1979;CEPM, 1980;Chamley et al, 1980) and also is supported by the extent of resedimentation structures, high sedimentation rates, and absence of correlation between detailed li-thology and clay mineralogy. The abundance of Al-Fe smectites and kaolinite indicates the probable importance of pedogenic processes on the landmasses and the existence of hot climates with alternating wet and dry seasons (Chamley, 1979).…”

“…Als.-Lorr., 23. Maillot, H., andRobert, C, 1980. Minéralogie et géochimie des sediments crétacés et cénozoiques dans 1'Océan Atlantique sud (marge africaine, dorsale médio-atlantique).…”

Mineralogy of Cenozoic Sediments Cored during Deep Sea Drilling Project Leg 79 as Determined by X-Ray Diffraction

“…The clay mineral suite is dominated by illite, indicating a terrigenous supply, whereas the origin of the fibrous silicates palygorskite and sepiolite is unclear. Chamley et al (1980) ascribe the fibrous clays in sediment samples from the Moroccan coast to the presence of alkaline marginal basins where they were formed and later redeposited in turbidites off the African continent. A notable feature in some samples was the shape of the fibers that obviously were broken during transport.…”