Original paper

Mineralogical and lithofacies-controlled variation of palygorskite in Neogene siliceous-calcareous coastal deposits in geodynamically stable (Qatar) and mobile settings (Uzbekistan)

Dill, Harald G.; Kaufhold, Stephan


Palygorskite was investigated in Neogene sedimentary series representative of the basin- and landward areas of siliceous and calcareous linear shoreline environments in a mobile (Tien Shan Foreland Basin, Uzbekistan) and stable geodynamic setting (Arabian Shield, Qatar). A sedimentological-mineralogical approach has been taken using lithofacies types to determine the impact of climatic conditions, intrabasinal (formation of the environment of deposition) and extrabasinal (weathering and denudation of source rock) processes on the evolution of palygorskite and lithofacies catenas to demonstrate the influence of the geodynamic setting on palygorskite formation. Based upon the mineralogical and sedimentological data, palygorskite may be expected in morpho-climatic zones (semi-arid to arid - marginal desert-like) stretching parallel to the equator between 20° and 40° N and S, respectively. In nature, palygorskite occurs in moderately to well sorted silt and fine-grained sand under neutral to moderately acidic conditions on floodplains, in overbank deposits, mixed flat to mud flat (intertidal deposits), and supratidal/marsh deposits grading into aeolian deposits. Source minerals are Mg-enriched mica-group, chlorite-group or smectite-group phyllosilicates. As an intermediate repository Mg-bearing carbonates may also act as a source of Mg.In mobile and stable geodynamic settings, a well-balanced ratio of uplift-erosion vs. residence time - chemical weathering is crucial to its formation. In terms of sequence stratigraphy, palygorskite is a negative marker ("palygorskite low") of un/disconformities/sequence boundaries and a positive marker ("palygorskite high") of maximum flooding surfaces.


palygorskitegeodynamic settingclimateenvironment of depositionsource rockcoastlithofaciescatenauzbekistanqatar