Identification of fluvial architectural elements of meandering systems by paleosols (Upper Freshwater Molasse, North Alpine Foreland Basin, SW-Germany)

Maurer, H.; Buchner, E.

doi:10.1127/1860-1804/2007/0158-0271

Cited by 4 publications

(2 citation statements)

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“…12). Although these modes may resemble features of topographic "highs" and "lows" suggested by Ulbig (1994Ulbig ( , 1999, they are based on the fluvial-lacustrine depositional environment of the anastomosing to braided river system and associated palaeosols of the UFM (Schmid, 2002;Maurer & Buchner, 2007). This circumvents the problematic preservation of unconsolidated volcanic ash on topographic "highs" (Ulbig, 1994) in a strongly seasonal climate and the inherent dryness of such topographic "highs" (Böhme et al, 2007) that contradicts the sedimentological evidence of moist soils and wetlands (Unger, 1996;Schmid, 2002;Maurer & Buchner, 2007;Abdul-Aziz et al, 2010).…”

Section: B E N T O N I T E a N D C A R B O N At E F O R M At I O Nmentioning

confidence: 87%

“…zones of a basement high (Unger, 1981(Unger, , 1999Abdul-Aziz et al, 2010). The deposits being mined at present are limited to the 14.7 ± 0.2 Ma main bentonite horizon (Abdul-Aziz et al, 2010) in the upper part of the fluviatile Nördlicher Vollschotter (NV) sand and gravel unit and floodplain sediments of the Sand-Mergel-Decke (SMD) formed in an anastomosing to braided river system (Schmid, 2002;Maurer & Buchner, 2007) of the Upper Freshwater Molasse (UFM) (Vogt, 1980;Unger & Niemeyer, 1985;Unger et al, 1990;Ulbig, 1999). Ulbig (1999) invoked topographic "highs" and "lows" to explain sedimentological and depositional differences in the bentonites.…”

Section: Geological Settingmentioning

confidence: 99%

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A strontium isotope and trace element geochemical study of dolomite-bearing bentonite deposits in Bavaria (Germany)

Köster

Hölzl²,

Gilg

2017

Clay miner.

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The Landshut bentonites that formed from Ca- and Mg-poor rhyolitic tuffs in a fluviatile-lacustrine depositional environment of the Miocene Upper Freshwater Molasse, southern Germany, contain abundant palustrine, pedogenic and groundwater carbonates. Geochemical analyses of dolomites, calcites and smectites from bentonites of various environments by X-ray diffraction, thermal ionization mass spectrometry, inductively coupled plasma-mass spectrometry, and handheld X-ray fluorescence yield new insights into the compositions of fluids and sources of imported components involved in carbonate formation and bentonitization, as well as the timing of bentonite formation. Evaporated, Sr-rich brackish surface water with a molar Mg/Ca ratio of 2–5, derived mostly from the weathering of detrital carbonates, was involved in dolomite and bentonite formation in palustrine and some pedogenic environments. However, Sr-poor groundwater with a molar Mg/Ca ratio of ∼ 1 and a stronger silicate weathering component caused bentonite and calcite formation in strictly pedogenic and groundwater settings. The 87Sr/86Sr and molar Mg/Ca in the smectite interlayers indicate later cation exchange with water having more radiogenic Sr sources and smaller molar Mg/Ca ratios. The Rb-Sr data indicate the common presence of detrital illitic phases in the <0.2 μm fractions of the bentonites. Cogenetic palustrine dolomite and a single smectite residue sample which lacks this detrital illitic phase provide an age constraint for bentonitization at 14.7 ± 4.1 Ma identical to primary ash deposition. Thus a rapid onset of bentonitization of accumulated ash and dolomite formation in evaporation-driven wetland environments is indicated for the genesis of the Landshut bentonites.

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