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11th ICRS Abstract book - Nova Southeastern University

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1-21<br />

Coral Reef Development Along The Windward Platform Margin Since The Plio-<br />

Pleistocene: Southern Exuma Cays, Bahamas (Dedicated To Robert F. Dill, 1927-<br />

2004)<br />

Paul J. HEARTY* 1 , Donald F. MCNEILL 2<br />

1 GeoQuEST Research Centre, School of Earth and Environmental Sciences, <strong>University</strong><br />

of Wollongong, Australia (paulh@uow.edu.au), Wollongong, NSW, Australia, 2 MGG-<br />

RSMAS, <strong>University</strong> of Miami, Miami, FL<br />

The surface geology and two 33-m cores from the Exmas contain 11 limestone-paleosol<br />

“couplets” (C1 to C11 – older to younger), revealing depositional cycles extending back<br />

to the Plio-Pleistocene. The couplets are composed of marine limestone and terra rossa<br />

paleosol-karst exposure surfaces. Amino acid racemization and paleomagnetic reversals<br />

provide a functional chronostratigraphy for the couplets. At the base of the more<br />

bankward Core #2, couplets C1 to C3 contain the coral Stylophora, generally associated<br />

with the Plio-Pleistocene. The overlying C4 complex consists of several meters of dense<br />

reddish paleosols and thin intertidal lenses. These C4 paleosols bracket the Brunhes-<br />

Matayuma boundary (0.78 Ma; MIS 19?), and collectively equate with the “Big Red<br />

Soil” recognized on Bermuda and Hawaii. This interval comprises a succession of much<br />

lower highstands reflecting more interglacial continental ice from 0.5-1.0 Ma. Younger<br />

units C5 through C11 were deposited 0.5 Ma to present, and record lesser-known middle<br />

Pleistocene sea levels (MIS 15 @ -15 m, MIS 13 @ -7 m, and MIS 7 @ -18 m). In<br />

contrast, important interglacials during MIS 11 and 9 left little sedimentary evidence,<br />

probably due to deep flooding of the platform, and the dearth of early Pleistocene<br />

antecedent topography on which to “hang” deposits.<br />

Sea-level cycles across the Plio-Pleistocene show a general progression from reefal<br />

components to predominantly non-skeletal sands. Plio-Pleistocene highstands (3.0? - 1.0<br />

Ma) are obscured below present sea level by subsidence. Corals are a key component of<br />

units C2, C3, C4 in Core #2 and unit C6 in the more seaward Core #1. A long period of<br />

subaerial exposure from 1.0-0.5 Ma was followed by several important mid to late<br />

Pleistocene highstand carbonate accretionary events during which the platform margin<br />

extended to its present position over 3 km eastward.<br />

1-22<br />

Mid-Brunhes First High Amplitude Transgression(s): Platform Top and Siliciclastic<br />

Shelf Contemporaneous Re-flooding Recorded on the Slopes of Great Bahama Bank<br />

and Central Belize Barrier Reef<br />

Andre DROXLER* 1 , Brooke E. CARSON 2<br />

1 Earth Science, Rice <strong>University</strong>, Houston, TX, 2 Shallow Marine Stratigraphy Team,<br />

Chevron Energy Technology Company, Houston, TX<br />

Last 5 My ice volume variations recorded in stacked, globally distributed, benthic oxygen<br />

records, clearly show a systematic late Pliocene and early Pleistocene ice volume<br />

increase following an early Pliocene sea level highstand estimated to be 15 to 25 m<br />

higher than current sea level. This systematic ocean base-level fall was terminated by two<br />

mid Brunhes high amplitude transgressions at the MIS 16-15 and MIS 12-11 glacial to<br />

interglacial deglaciations. On the slopes of Great Bahama Bank (GBB) and central Belize<br />

Barrier Reef (BBR), a series of five-six stacked and contemporaneous highstand wedges<br />

are observed and identified as being linked to the MIS 15-13, 11, 9, 7, 5, and 1<br />

interglacial stages. Each package is defined by high concentration and/or mass<br />

accumulation rates of bank derived fine aragonite sediment bounded by intervening late<br />

glacial intervals enriched in Mg calcite cement corresponding to marine hardgrounds on<br />

the western margin of GBB and intraclasts-rich levels with coarser grain concentrations<br />

on the slope off the BBR. The highstand wedges are overlying an interval in both areas<br />

with lower bank-derived aragonite concentration and/or mass accumulation rates, higher<br />

pelagic calcite concentrations, and overall lower sedimentation rates. Based upon these<br />

observations, the two mid-Brunhes major MIS 16-15 and MIS 12-11transgressions<br />

correspond to first a partial and then a full re-flooding of GBB top and the siliciclastic<br />

fluvial plain established at lower base level during the late Pliocene and early Pleistocene<br />

sea level regression in Belize. These two mid-Brunhes transgressions have most likely<br />

triggered also the onset of modern barrier reefs along the Queensland and New Caledonia<br />

margins, the Florida Keys, and globally modern atolls. The MIS 12-11 transgression<br />

marks the first time interglacial atmospheric CO2 concentrations reached late Brunhes<br />

values between 280-295 ppm which has been suggested to be related to the global neritic<br />

carbonate re-establishment.<br />

Oral Mini-Symposium 1: Lessons From the Past<br />

1-23<br />

Late Miocene To Recent Coral Community Dynamics in The Gulf Of California<br />

Ramón LÓPEZ-PÉREZ* 1<br />

1 Instituto de Recursos, Universidad del Mar, Puerto Angel, Mexico<br />

Hermatypic coral studies in the Gulf of California have focused mainly on the distribution,<br />

abundance, ecology, and biogeography of modern species, but relatively few of these works<br />

have studied fossil corals. Miocene to Pleistocene coral communities in the Gulf of California<br />

were targeted in order to assemble a detailed geologic and taxonomic framework for already<br />

known and new coral bearing units. In general, coral bearing units are small and represent<br />

single spatio-temporal growth episodes ranging in age between late Miocene to late Pleistocene.<br />

Identification of recently collected specimens reveals that previously recognized coral species<br />

probably represent ~ 50 % of the Gulf of California fauna. Cluster analysis, multidimensional<br />

scaling and analysis of similarity of presence/absence and relative abundance data demonstrated<br />

that Gulf of California coral reef assemblages experienced larger temporal differences in<br />

species composition and relative abundance than expected by chance. Coral species originated<br />

and were added to the species pool during late Miocene-early Pliocene and Pleistocene. Gulf of<br />

California assemblages consisted of locally originated Caribbean-like species between late<br />

Miocene and late Pliocene when extinction peaked at the Plio-Pleistocene transition. During the<br />

Pliocene assemblages consisted of a mix of extinct and living species co-occurring within and<br />

among localities, but immediately after the demise of pre-turnover taxa, living Indo-Pacific<br />

immigrant species dramatically increase in number and relative abundance ruling out ecological<br />

replacement as the key factor in pre-turnover species extinction. The turnover is unique in that<br />

pre-turnover species origination resulted from the formation of the Gulf of California, and<br />

instead of reducing species richness, the extinction event triggered the long-distance<br />

colonization of species. More data and better resolved age dates are necessary to understand the<br />

cause of faunal turnover, and the relative importance of biological and environmental factors in<br />

the faunal change.<br />

1-24<br />

Caribbean Coral Reef Types From A Mixed Siliciclastic-Carbonate Setting: Miocene-<br />

Pliocene Of The Dominican Republic<br />

Donald MCNEILL* 1 , James KLAUS 2 , Ann BUDD 3<br />

1 Marine Geology & Geophysics, Rosenstiel School - <strong>University</strong> of Miami, Miami, FL,<br />

2 Department of Geological Sciences, <strong>University</strong> of Miami, Coral Gables, FL, 3 Department of<br />

Geoscience, <strong>University</strong> of Iowa, Iowa City, IA<br />

Geologic models of ancient Caribbean coral reefs that occur in predominantly siliciclastic<br />

settings have developed and diversified since the 3rd Coral Reef Symposium in 1977. The<br />

objective of this study is to characterize the styles of reef development in these mixed<br />

siliciclastic-carbonate settings from the exceptionally well-preserved fossil reef deposits in the<br />

Cibao Basin, northern Dominican Republic. Building on the mixing classification of Mount<br />

(1984), we recognize three main styles (geometries) of "in situ" carbonate (reef) deposition<br />

within siliciclastics. These include: 1) late Miocene stacked patch reefs-these reefs occur as<br />

isolated patches approximately 20-30 m thick and 300-400 m wide as part of a shallow<br />

clinoformal shelf. Lowered sea level and initial transgression provided conditions favorable to<br />

patch reef initiation and development; 2) late Miocene-early Pliocene bedded coral in mudthese<br />

reefs occur as either thick beds (3-6 m thick) of mud with abundant coral and coral<br />

fragments scattered throughout, or as distinct, cyclic coral beds (0.5-1 m thick) interbedded with<br />

mud beds (

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