Hardy, Peter G. & Broadhurst, Frederick M. 1978 04 IS: Refugee communities ofCarbonirola
Sparse elongate forms of the non‐marine bivalve Carbonirola are associated with an abundance of trace fossils comprising resting traces (Cubichnia) referable to Lockeia, trails (Repichnia) and escape shafts (Fugichnia), all in arenaceous sediments of the Upper Carboniferous. Associated organic‐rich argillaceous sediments contain the well‐known, abundant and highly variable Carbonirola body fossil faunas. The latter we interpret (in common with other workers) as the remains of shells preserved in what was the typical life environment (characterized by muddy sediments and slow rates of sedimentation). The elongate shells associated with escape shafts we interpret as the only form of Carbonicola capable of escape upwards from burial by rapid sedimentation. For such fugitives from preexisting ‘established communities’ we propose the term ‘refugee community’.
Broadhurst, F. M. & Simpson, I. M.: Bathymetry on a Carboniferous reef.
In the Lower Carboniferous deposits of Castleton, Derbyshire, well bedded shelf limestones, apparently of shallow water origin, pass northwards into a marginal tract of poorly bedded apron‐reef limestones which dip at about 30° downwards and away from the ‘shelf’. Geopetal infillings of shell cavities in the apron‐reef indicate only minor movement since deposition, and the observed dip must be due to deposition on a sloping sea floor. At certain times this sea floor was colonised by stromatolitic algae and corals such as Lithostrotion at the apron‐reef crest where there was minimum water depth, followed to progressively increasing depths by (1) a fauna dominated by the coral Michelinia, (2) a fauna of small brachiopods, bryozoa, molluscs, trilobites, and other organisms and (3) a fauna dominated by Pseudamussium. At other times crinoidal debris was the dominant component of the apron‐reef, when an alignment of crinoid stems parallel to the dip of the slope occurred at low levels, but a random orientation at the apronreef crest. Other sediments on the apron‐reef are apparently devoid of macrofossils. Volcanic activity occurred during the development of the apron‐reef, and it is suggested that uplift of the shelf area preceded the subaerial flow of a lava tongue which reached and plunged down the apron‐reef slope and into the sea.
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