11th ICRS Abstract book - Nova Southeastern University
11th ICRS Abstract book - Nova Southeastern University
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 (