Premium
Abiogenic silica layers within a fluvio‐lacustrine succession, Bolzano Volcanic Complex, northern Italy: a Permian analogue for Magadi‐type cherts?
Author(s) -
KRAINER KARL,
SPÖTL CHRISTOPH
Publication year - 1998
Publication title -
sedimentology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.494
H-Index - 108
eISSN - 1365-3091
pISSN - 0037-0746
DOI - 10.1046/j.1365-3091.1998.00164.x
Subject(s) - abiogenic petroleum origin , geology , diagenesis , quartz , petrography , geochemistry , permian , volcano , sediment , lithification , mineralogy , paleontology , methane , structural basin , ecology , biology
Thin layers of chert occur within a fluvio‐lacustrine succession sandwiched between acidic volcanic rocks of the Lower Permian Bolzano Volcanic Complex in northern Italy. These cherts are interpreted as analogues to Magadi‐type abiogenic chert known from modern volcanic lake settings. Soft‐sediment deformation features, shrinkage cracks, and well‐preserved palynomorphs document very early diagenetic silica precipitation, volume loss by dehydration, and consolidation prior to mechanical compaction of the sediment. Transformation to quartz and concomitant (re)crystallization resulted in a variety of silica textures, dominated by microflamboyant quartz. The oxygen isotopic composition of chert samples ranges from +25·4 to +29·0‰ and is negatively correlated with crystal size and ordering.