Palaeogeographic controls on palygorskite occurrence in Maastrichtian-Palaeogene sediments of the Western High Atlas and Meseta Basins (Morocco)

Abstract

AB ST R ACT : The Maastrichtian-Palaeogene series of the Western High Atlas and Meseta Basins in Morocco are particularly rich in palygorskite. The present work is aimed at clarifying the genesis of palygorskite from the interbedded facies and gaining an understanding of their relationships with the depositional environment. The mineralogical characteristics of palygorskite from these series were studied by X-ray diffraction (XRD) and electron microscopy (SEM/TEM). The palygorskite content and microstructure show large geographical and stratigraphical variations in the deposits studied. The palygorskite occurrence is directly related to palaeobathymetry, since it is the dominant clay mineral in shallow marine and restricted environments. According to the morphology of palygorskite crystallites, four types of textures were distinguished. These types of palygorskite are polygenetic, formed by chemical precipitation, by the recrystallization of smectite clays or reworked by wind or water from sub-aerial environments. The difference between the two studied sub-basins with respect to palygorskite occurrence is attributed to the palaeomorphology of the hinterlands, to the tectonic differentiation and to the physical-chemical conditions of seawater.

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.…”

Occurrences and genesis of palygorskite/sepiolite and associated minerals in the Barzaman formation, United Arab Emirates

“…Palygorskite and sepiolite are fibrous clay minerals typically formed in dry and warm climates at specific pH and concentrations of dissolved SiO 2 (Isphording, 1973;Badraoui et al, 1992;Daoudi, 2004;Hillier & Pharande, 2008;Knidiri et al, 2014). The authigenic formation of sepiolite and palygorskite requires alkaline solutions with high Si and Mg activities (Golden et al, 1985;Birsoy, 2002;Hong et al, 2007).…”

Customised display of large mineralogical (XRD) data: Geological advantages and applications

“…Using a 3D approach provided a more intuitive and complete scenario, fully in agreement with the principles brought forward by Wu and Shah (2004) to: "reduce cognitive load by making information explicit and F I G U R E 3 Schematic representation of the standard procedure followed during XRD data treatment (see text for potential limitations). (A) Example of the results obtained by search/match software used to identify each mineral present at relevant proportion (in Knidiri et al, 2014 and extracted from https:// www.scien tistl ive.com/conte nt/xrd-analy sing-powde rs). (B) Semi-quantitative calculation of the abundance of each mineral (integral intensity, example adapted from Morris et al, 2003).…”