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Carbonate petrography as an indicator of climate and sea-level changes: new data from Bahamian Quaternary units (1996)

KINDLER, PASCAL ; HEARTY, PAUL J.

Oxford, UK : Blackwell Publishing Ltd

Sedimentology 43 (1996), S. 0

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ISSN: 1365-3091

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Geologie und Paläontologie

Notizen: Coeval stratigraphic units of similar petrology occur throughout the northern Bahamas islands. The petrographic composition of these limestones provides clues about regional sea level and climate changes during the late Quaternary. At least eight fossil shoreline units, which are linked to transgressive episodes between the middle Pleistocene and the late Holocene, are recognized in the Bahamas. The petrographic composition of these units is either dominated by ooids and peloids or by bioclasts. Sedimentological observations demonstrate that oolitic-peloidal units were formed when sea level was higher than today, whereas skeletal units were deposited at or below modern ordnance datum. Skeletal units may reflect times of partial, or modest platform flooding, when the bulk of sediments brought to islands originates from bank-margin reefs. In contrast, oolitic-peloidal units correspond to major flooding events and active water circulation on the bank top. Cement fabrics further show that the early diagenesis of oolitic units took place during warm and humid climatic conditions, whereas skeletal rock bodies underwent subaerial diagenesis during drier climatic conditions characterized by marked seasonal changes. This example from the Bahamas suggests that compositional analysis of limestone from fossil carbonate platforms could be used for resolving ancient climate and sea-level changes.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1046/j.1365-3091.1996.d01-11.x

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PRESERVATION OF TRACE FOSSILS AND MOLDS OF TERRESTRIAL BIOTA BY INTENSE STORMS IN MID-LAST INTERGLACIAL (MIS 5c) DUNES ON BERMUDA, WITH A MODEL FOR DEVELOPMENT OF HYDROLOGICAL CONDUITS (2011)

HEARTY, PAUL J. ; OLSON, STORRS L.

Society for Sedimentary Geology (SEPM)

In: PALAIOS 26: 394-405.

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Publikationsdatum: 2011-07-01

Beschreibung: We document massive deposition of carbonate sands along the south shore of Bermuda that were emplaced during one or two great storms during the last interglacial. As determined by their stratigraphic position and geochronological data, these deposits formed during marine isotope substage (MIS) 5c ca. 100 ka ago. Within a leeward set of eolian beds, evidence of a living landscape was preserved that includes delicate footprints of a shorebird (Scolopacidae, Catoptrophorus) preserved in frothy dune foreset beds. In the same stratigraphic unit, outlines of a standing forest of palm trees (Sabal bermudana), some evidently with fronds in place, were molded in the fine carbonate dune sand. All available evidence points to an MIS 5c sea level positioned several meters below the present datum, which would require great intensity of storms to transport such voluminous deposits well above present sea level. Waves and storm currents transported loose sediments from the shallow shelf onto the shore, where hurricane winds piled up sand sufficiently deep to bury established forests of 8- to 10-m-tall trees. Evidence of such powerful storms preserved in the rock record is a measure of the intensity of past hurricanes, and a possible bellwether of future storm events. Entombment of the trees involved rapid burial and cementation creating external molds in limestone, a process that is important in the development of vertical hydrological conduits commonly observed in eolianites.

Print ISSN: 0883-1351

Digitale ISSN: 0883-1351

Thema: Geologie und Paläontologie

Publiziert von Society for Sedimentary Geology (SEPM)

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