Comparative influence of burial depth on the clay mineral assemblage of the Agadir-Essaouira basin (western High Atlas, Morocco)

Abstract

In the western High Atlas basin, the evolution of the clay assemblage of the Upper Jurassic–Cretaceous sedimentary series is controlled by palaeogeographic changes of the basin and by burial diagenesis.The effects of burial are expressed by an increase in the proportions of illite and chlorite with depth, a decrease of expandability of smectite minerals and by a decrease in the Kübler Index.Kaolinite is preserved at greater depths than smectite, but also tends to diminish in abundance. TEM observations show that idiomorphic pseudo-hexagonal crystals of illite increase in size and abundance downwards, especially in the sandy levels.In the Agadir section, the main change in the clay mineral evolution related to late diagenesis occurs at the Mid-Albian, corresponding to a burial depth of about 1800 m; in the Essaouira section it occurs at the Lower Tithonian at a burial depth of about 2100 m.Considering the different geothermal gradient between Agadir (36ºC km–1) and Essaouira (27ºC km–1), the disappearance of smectite occurs at the same temperature in these two sites (60 to 65ºC).

Main parameters influencing the plastic behavior of clays used for traditional ceramics production

“…Figure 3: Classification of studied clay raw materials based on the sand-silt-clay ratios (Shepard, 1954). Daoudi et al (2010) show that the burial diagenesis is the main factor controlling the genesis of the clay assemblages of the sedimentary series of the Lower Mesozoic of the Western High Atlas. The effects of burial on these clay assemblages are expressed as the downward increase in the proportions and size of the illite crystallites.…”

New thermocronological data of the Cretaceous-Cenozoic clastic sequences from the VINCHINA basin: Linkage between burial, exhumation and thermal flow variations

“…Although some studies of paleoclimatic and paleoenvironmental conditions of different geological periods based on this proxy take into account the influence of diagenetic processes (eg. Daoudi et al, 2010), many others do not consider such influence or subjectively assume that diagenesis can be negligible (e.g., Thiry, 2000;Net et al, 2002;Ruffell et al, 2002;Daoudi et al, 2008;Raucsik and Varga, 2008;Bauluz et al, 2014). Similarly, many studies that attempt to establish paleothermal conditions, geodynamic contexts and geothermal gradients do not take into account possible compositional variations related to paleoenvironmental changes or primary source variations (e.g., Hower et al, 1976;Merriman and Peacor, 1999;Collo et al, 2011;Clauer and Lerman, 2012).…”

Clay minerals in shales of the Lower Silurian Longmaxi Formation in the Eastern Sichuan Basin, China

“…The types and distribution of clay minerals vary in different regions and geological formations due to a number of factors. Analysis of clay-mineral composition, genesis and distribution may be used not only for palaeo-environmental reconstructions and records of diagenetic conditions, but may contribute in the prediction of oil and gas reserves (Daoudi et al, 2010;Zhang et al, 2013).…”