A fragment of a shell or fossil forming part of a sedimentary rock.
〔地质〕生物岩碎屑
Example sentencesExamples
Within the upper beds of the Mount Hyatt Member bioturbation is intense and many bioclasts appear to have been rotated to high angles.
The offset in these two curves reflects the lengthy residence time for bioclasts in this high wave energy coastal environment, and a component of sediment recycling from older barriers.
The erosive bases and stacking of bivalve shells indicate removal and redeposition, and suggest that these shells and other bioclasts were removed from the platform and redeposited on the slope by storms.
The average size of bioclasts is 2-3 cm. Small volcanic clasts appear dispersed in some beds.
Leperditiid shells are the dominant bioclasts and trilobite fragments are rare.
Derivatives
bioclastic
adjectivebʌɪə(ʊ)ˈklastɪk
Geology
The boundaries are sharp and erosive, removing most of the foreshore deposits of the underlying shoreface units, and are paved by a lag of bioclastic debris.
Example sentencesExamples
The middle member is dominated by gray silty shale grading upwards to bioclastic siltstone interbedded with bioclastic limestone.
The facies consists mainly of brownish grey laminated bioclastic packstone and thinly bedded cherts.
The lower part is a 6 m thick sandstone whose base is characterized by closely spaced erosion surfaces, common phosphate nodules, black quartz pebbles and fragmented bioclastic debris.
The bioclastic facies of the Upper Domerian and Upper Toarcian Limestone Mbrs suggest periods of shallower sedimentation above storm wave base.