bioturbation

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bioturbation

[¦bī·o·tər′bā·shən]
(geology)
The disruption of marine sedimentary structures by the activities of benthic organisms.
References in periodicals archive ?
2) show an upward progression into a highly bioturbated facies with abundant trace fossils, that lacks turbiditic structures.
Photographs indicate that margin sediments are generally highly bioturbated (Fig.
The lithology of the Clayton Formation is quite distinct from that of either the overlying Porters Creek or underlying Owl Creek Formations, and contains a clay pit (Golden Cat Company Clay Pit) which consists of 5 to 6 meters of bioturbated, dark green, glauconitic, micaceous, fine to medium sands alternating with layers of dark gray clay.
Subunit D consists of greenish, laminated, non-bioturbated, clayey siltstones that grade upward into massive to cross-bedded bioturbated, fossiliferous sandstones.
Each cycle is composed of a basal dark, laminated section, grading upward into a gray, wispy laminated interval, and capped by a white, bioturbated layer.
It is interpreted as a condensed section (Echols 1984) based upon: occurrence of ammonites from four midcontinent ammonite range zones, undulatory bottom surface, bioturbated surface, and abundant ironstone and phosphate concretions.
2) shows three major depositional units, each heavily bioturbated by Chondrites and Teichichnus.
Thin sequences of bioturbated fine-grained sandstone are cross bedded with fine-grained sandstone and gray mudstone.
The latter two objects were found in bioturbated context and may reflect contamination from more recent strata.
4) 5-7 cm light yellowish to brownish hard feld-spathitic layer, occasionally containing elongated or irregularly shaped concretions of pyrite reaching 5 cm in size, bioturbated in places.
10 m) consists of medium- to thick-bedded, partly bioturbated, brownish-grey, slightly argillaceous dolostone with thin irregular wavy interbeds of dark grey dolomitic marlstone.