The Origin of the Supposed Tufa Bands in Carboniferous Reef Limestones

Abstract

Thin bands of fibrous calcite occur in the Carboniferous reef limestones of northern England and have been regarded as bands of primary tufa within a marine limestone series. A study of these fibrous bands has been carried out and the results show conclusively that they are in fact secondary recrystallization structures.

Diagenetic fabrics in some British Dinantian limestones

“…This mosaic is the "reef-tufa" of earlier authors. Its typical drusy fabric would imply that "reef-tufa" is not, after all, a recrystallized calcite-mudstone as proposed by W. W. Black (1952).…”

“…Serial photographs of bubble rafts by Bragg and Nye (1947) and of cell enlargement in foam by C. S. Smith (1952, Fig. 12) are worthy of study.…”

Middle Jurassic stromatactis mud-mounds in the Pieniny Klippen Belt (Carpathians) — A possible clue to the origin of stromatactis

“…The suggested origins for stromatactis included internal erosion and reworking of small cavities (e.g. Kukal, 1971;Wallace, 1987;Bridges and Chapman, 1988;Matyszkiewicz, 1993Matyszkiewicz, , 1997, dewatering or escape of fluids (Heckel, 1972;Desbordes and Maurin, 1974;Bernet-Rollande et al, 1981), neomorphism or recrystallization of the calcareous mud (Black, 1952;Orme and Brown, 1963;Ross et al, 1975), dynamic metamorphism (Logan and Semeniuk, 1976), slumps (Schwarzacher, 1961) and fresh-water karstification (Dunham, 1969). Most recent ideas involve frozen clathrate hydrates in the calcareous mud, after which the stromatactis cavities remained (Krause, 2001) or the cavities are interpreted as a result of sedimentation of stirred polydisperse sediment (Hladil, 2005;Hladil et al, 2006Hladil et al, , 2007.…”

Lithology and origin of Middle Ordovician calcareous mudmound at Meiklejohn Peak, southern Nevada

“…Several observations indicate that, irrespective of what the origin of Stromatactis may be, the shape and size of the radiaxial crystals, and possibly the whole radiaxial mosaic as such, is not original but a result of diagenetic processes. The radiaxial mosaic has demonstrably incorporated skeletal particles (Black, 1952;Orme and Brown, 1963;Jaanusson, 1975) and grown at their expense. The material from the core of the Meiklejohn Peak mound shows numerous examples of this phenomenon (figs.…”

“…These mounds resemble somewhat younger Ordovician features in the Siljan district, central Sweden (Thorslund, 1936;Thorslund and Jaanusson, 1960, p. 24-35), and Carboniferous "knoll reefs" of northwest and west-central Ireland ( Schwarzacher, 1961;Lees, 1964). Development of sparry calcite in the main part of the biggest of the Nevada mudmounds may have some relation to structures called Stromatactis, well known in middle and upper Paleozoic mudmounds in Western Europe (Black, 1952;Bathurst, 1959;Schwarzacher, 1961;Lees, 1964;Jaanusson, 1975). In the basal part of the Nevada mound there is enigmatic, thinly interlayered calcilutite and sparry calcite which together resembles "sheet spar" described by Lees (1964, p. 523-524) and "zebra limestone" described by Fischer (1964, p. 115, figs.…”