“Calcispheres” as a source of lime mud and peloids – evidence from the early Middle Devonian of the Prague Basin, the Czech Republic

Abstract

Several types of peloids are present in the Lower and Middle Devonian limestones of the Prague Basin (uppermost part of the Třebotov Limestone of the Daleje-Třebotov Formation and Choteč Formation, uppermost Emsian-Eifelian) and are interpreted as being of calcispheral, echinoderm, and/or calcimicrobial origin. Possible mechanisms of peloid formation, the mode of life of calcispheres and their role in the accumulation of Paleozoic lime mud are discussed. Mass occurrences of peloids and calcispheres are characteristic features of the Choteč Formation (Eifelian, costatus-kockelianus conodont zones). It is concluded that specific environmental conditions, such as a higher nutrient load, existed during the sedimentation of this unit, probably in response to the Basal Choteč event.•

Environmental changes close to the Lower–Middle Devonian boundary; the Basal Choteč Event in the Prague Basin (Czech Republic)

“…Transport took place from the shallow water, probably from the photic zone (the shallowwater origin of the grainstone beds was suggested already by Chlupáb 1959). As suggested by Berkyová and Munnecke (2010), the source area (which is not preserved) was probably somehow sheltered, probably by a crinoidal bar, and poorly agitated so that micritization and peloid formation could have taken place. An origin within the photic zone is probable, considering the co-occurrence of Girvanella (which was found with other material transported down-slope) and the activity of bioeroders.…”

“…The peloids of the Choteb Formation were discussed in detail by Berkyová and Munnecke (2010). The latter authors recognized several kinds of peloids in the Choteb Formation and, based on the several stages of grain degradation recorded, interpreted the origin of peloids as (1) totally micritized calcispheres (e.g., Fig.…”

The largest Lower Devonian placoderm - Antineosteus rufus sp. nov. from the Barrandian area (Czech Republic)

“…Only a few taxa of microflora and microfaunal foraminifera were identified by Dieken (1996). Lack of other microelements, calcispheres and peloids (in contrast to its deeper water equivalent -the Třebotov Limestone) was proved by Berkyová & Munnecke (2010).…”

Emsian-Eifelian lingulate brachiopods from the Daleje-Třebotov Formation (Třebotov and Suchomasty limestones) and the Choteč Formation (Choteč and Acanthopyge limestones) from the Prague Basin; the Czech Republic

“…Various types of peloids, micritized grains, accumulations of calcispheres and prasinophytes at specific levels represent characteristic features of this unit and are regarded as a result of environmental changes, e.g. higher nutrient load, linked to the Basal Choteč Event (Berkyová & Munnecke 2010). Apart from this, the Choteč limestone is characterised by an impoverished fossil content (see also Chlupáč et al 1979;Chlupáč & Kukal 1986.…”