Agglutinated foraminifera from the Sydney Coalfield, Nova Scotia: Their use as indicators of sea-level changes in Carboniferous coal-bearing strata
- Dalhousie Univ., Halifax, Nova Scotia (Canada). Centre for Marine Geology
Agglutinated foraminifera and arcellaceans (the camoebians) were examined from Carboniferous (Late Westphalian-Stephanian) cyclothems in the Sydney Basin of Nova Scotia. Their presence confirms that the laterally extensive coal seams, limestones, mudstones and carbonaceous shales were deposited in a paralic setting. Four distinctive assemblages are documented from the coal-bearing strata, and these may be used as accurate paleo sea-level indicators on the basis of the modern distribution of similar assemblages. Mixed assemblages dominated by Ammobaculites characterize siltstones overlying the coal seams, an association typical of mineralic substrates within modern estuarine environments. Assemblages dominated by small, finely agglutinated specimens of Ammotium and Ammobaculites occur in organic rich strata between coal seam splits. Similar assemblages are found in modern salt marshes and upper estuarine settings. Trochammina dominated assemblages occur in mudstones underlying the coal seams. Such assemblages are typical of higher elevations in modern brackish and saline marshes. Monotypic assemblages of the arcellacean Difflugia are also found in the seat earths below coal seams. Similar associations occur today in mineralic substrates below modern freshwater floating marshes. The presence of a Trochammina assemblage has aided recognition of a maximum flooding (transgression) surface below the base of an incised paleovalley, interpreted as a type 1 sequence boundary, in the Bonar cyclothem of the Sydney Basin. The valley incision is attributed to glacioeustatic sea-level lowering. The upper 10m of the 25m thick valley fill contains assemblages of Difflugia, which are succeeded by Trochammina assemblages within the seat earth beneath the coal at the top of the cyclothem.
- OSTI ID:
- 5702665
- Report Number(s):
- CONF-921058--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 24:7; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
011000* -- Coal
Lignite
& Peat-- Reserves
Geology
& Exploration
ANIMALS
CANADA
CARBONIFEROUS PERIOD
COAL DEPOSITS
COAL SEAMS
DEPOSITION
DEVELOPED COUNTRIES
FLUCTUATIONS
FORAMINIFERA
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGY
INVERTEBRATES
LEVELS
MICROORGANISMS
MINERAL RESOURCES
NORTH AMERICA
NOVA SCOTIA
PALEOCLIMATOLOGY
PALEONTOLOGY
PALEOZOIC ERA
PROTOZOA
RESOURCES
SARCODINA
SEA LEVEL
STRATIGRAPHY
VARIATIONS