The uncertainties involved in extracting amplitude and frequency of orbitally driven sea-level fluctuations from shallow-water carbonate cycles

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doi: 10.1111/sed.12011
Author(s): Eberli, Gregor P.
Author Affiliation(s): Primary:
University of Miami, CSL-Center for Carbonate Research, Miami, FL, United States
Other:
University of Bern, Switzerland
ETH Zurich, Switzerland
Volume Title: Alpine sedimentology
Volume Author(s): Föllmi, Karl B., editor; Schlunegger, Fritz; Weissert, Helmut
Source: Alpine sedimentology, edited by Karl B. Föllmi, Fritz Schlunegger and Helmut Weissert. Sedimentology, 60(1), p.64-84. Publisher: Wiley-Blackwell, Oxford, United Kingdom. ISSN: 0037-0746 CODEN: SEDIAT
Note: In English. 103 refs.; illus., incl. sect., sketch map
Summary: In outcrops, shallow-water carbonates often form thick, vertically stacked, meter-scale, exposure-bounded depositional packages, here called carbonate cycles. Because the facies within carbonate cycles can be tied precisely to water depths, they are considered ideal for reconstructing past sea-level changes. There is, however, increasing evidence that these depositional cycles are unreliable recorders of both the frequency and the amplitude of orbitally driven sea-level fluctuations. Carbonate cycles record only a fraction of the amplitude of a sea-level cycle: a portion of the rise and nothing of the fall. Cores through the Pleistocene cycles on Great Bahama Bank illustrate this shortcoming. Although the amplitudes of the last nine sea-level changes are each a hundred meters or more, the thickness of the cycles varies from a few meters to ca 15 m. The lack of correlation between sea-level amplitude and cycle thickness is not eliminated for cycles deposited during times of lower sea-level amplitudes, for example, the Cretaceous. Upper Cretaceous cycles on the Maiella Platform margin document the irregularly filled accommodation space and the resultant variability in cycle thickness and frequency. Uncertainties in assessing the frequencies of sea-level changes from shallow-water carbonate cycles are caused by "missed beats" and meter-scale oscillations of sea-level within highstands that potentially produce cycles of very short duration. The random amplitude variability during the last 57 glacio-eustatic sea-level changes illustrates the difficulty of assessing "missed beats", where a sea-level fluctuation is not recorded because the sea-level rise does not reach the platform top. "Missed beats" are also produced by the depositional topography that is created by irregularly filled accommodation space. As a result, variable numbers of cycles are deposited across the platform. Further complicating orbital frequency analyses are decameter-scale oscillations of the sea-level during highstands. The amplitude of these sub-orbital sea-level oscillations (up to 17 m within the last interglacial, Marine Isotope Stage 5e) are sufficient to expose shallow platforms like Great Bahama Bank and subsequently produce an additional depositional cycle with similar facies successions. The combined effects of missed beats and oscillations within highstands are likely to produce cycles and hiatuses of variable duration that are difficult to extract from the rock record. Consequently, estimates of the orbital forcing mechanisms and frequencies from ancient shallow-water carbonate cycles carry large uncertainties. Abstract Copyright (2012), International Association of Sedimentologists.
Year of Publication: 2013
Research Program: DSDP Deep Sea Drilling Project
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Atlantic Ocean; Bahamas; Biofacies; Biostromes; Carbonate rocks; Caribbean region; Cenozoic; Cretaceous; Cycles; DSDP Site 166; Deep Sea Drilling Project; East Pacific; Equatorial Pacific; Foraminifera; Glacial environment; Glaciomarine environment; Great Bahama Bank; Interglacial environment; Invertebrata; Leg 17; Limestone; Maiella Platform; Marine environment; Mesozoic; Microfossils; Milankovitch theory; Modern analogs; Nannofossils; North Atlantic; North Pacific; Northeast Pacific; Orbits; Pacific Ocean; Plantae; Pleistocene; Protista; Quaternary; Sea-level changes; Sedimentary rocks; Shallow-water environment; Straits of Florida; Upper Cretaceous; West Indies
Coordinates: N034542 N034542 W1750448 W1750448
N250200 N250200 W0772400 W0772400
Record ID: 2013032381
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom