11th ICRS Abstract book - Nova Southeastern University

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Paleoecology Of Mio-Pliocene Free-Living Corals in The Northern Dominican
Republic And Neogene Evolutionary Patterns Of The Caribbean Region
James KLAUS* 1 , Ann BUDD 2 , Donald MCNEILL 3 , Scott ISHMAN 4
1 Department of Geological Sciences, University of Miami, Coral Gables, FL,
2 Department of Geoscience, University of Iowa, Iowa City, IA, 3 Rosenstiel School of
Marine and Atmospheric Science, Marine Geology and Geophysics, University of
Miami, Miami, FL, 4 Department of Geology, Southern Illinois University, Carbondale,
IL
Periods of accelerated origination and extinction have played a disproportionate role in
shaping the structure and ecology of Cenozoic coral communities in the Caribbean
region. This is most evident in the late Pliocene faunal turnover event in which
approximately 80% of Mio-Pliocene corals became extinct and more than 60% of species
now living in the region originated. Free-living meandroid corals were particularly hard
hit during this interval; only two species survive in the region today, Manicina
areolata and Meandrina brasiliensis. Diversity patterns based on new collections
and compiled records from the Caribbean region show that the diversity of free-living
meandroid corals increased throughout the Neogene. Two free-living meandroid corals
are known from the early Miocene, and diversity accumulated slowly during the middle
and late Miocene. During the latest Miocene and early Pliocene diversity more than
doubled from 11 to 24 species, before falling abruptly between 2 and 1 Ma from 22 late
Pliocene species to the two modern species. To better understand the ecology of freeliving
corals as well as their pattern of abrupt origination proceeding catastrophic
extinction, over 1,300 free-living coral specimens were collected from 21 localities in the
northern Dominican Republic ranging in age from 6.2 to 3.4 million years ago.
Preliminary results integrating benthic foraminifera and other environmental indicators
suggest that unlike modern M. areolata and M. brasiliensis, which are typically
associated with very shallow water grassflat environments, free-living corals of the
northern Dominican Republic had a much wider habitat range from grassflats to deeper
forereef environments. Given these environmental constraints we evaluate the patterns of
origination and extinction within the context of Neogene paleoceanographic events.
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Cenozoic Photic Reef And Carbonate-Ramp Habitats: A New Look Using
Paleoceanographic Evidence
Pamela HALLOCK* 1 , Luis POMAR 2
1 College of Marine Science, University of South Florida, St Petersburg, FL,
2 Departament de Ciencies de la Terra, Universitat de les Illes Balears, Palma de Mallorca,
Spain
Understanding biological and geochemical processes associated with modern coral reefs
is essential to interpreting fossil reefs and carbonate sedimentation. Yet recognizing the
limitations of uniformitarianism is equally crucial. Cenozoic carbonate-producing
ecosystems emerged from the remnants of Cretaceous biotas, evolving in the warm
alkaline oceans of a Greenhouse world, then modifying in response to developing
Icehouse conditions. The latter included stronger latitudinal and bathymetric temperature
gradients, declining carbon dioxide concentrations in the atmosphere and declining
calcium concentrations and alkalinity in the oceans. Paleocene-Eocene photic-dependent
carbonates tended to be dominated by calcitic coralline red algae and larger benthic
foraminifers (LBF), with aragonitic corals and calcareous green algae more restricted
temporally and spatially. Conceptual models suggest that episodic changes in ocean
circulation and thermocline stratification that accompanied high latitude cooling during
the Cenozoic provided impetus for turnover in chlorozoan biotas. For example,
comparison of Eocene through Miocene paleotemperature data on surface to thermocline
gradients with the history of LBF assemblages indicates that the latter were most diverse
and productive when deeper waters were warmest and gradients were weakest. Higher
extinction rates corresponded with times when surface to thermocline gradients
increased. In contrast, zooxanthellate corals, while relatively diverse in the Eocene, were
restricted as reef builders. As Icehouse conditions emerged, aragonite production by
corals and calcareous algae became more widespread, with a setback in the early and
middle Miocene when coralline algae again dominated. Moreover, the proliferation of
reef-building coralline algal taxa into shallow-water habitats in the late Miocene
paralleled the emergence of shallow-water corals and new clades of zooxanthellae,
indicating co-evolution of these critical reef taxa. Implications of these observations
support the hypothesis that deeper photic-zone (30-100 m) carbonate systems will survive
anthropogenically driven changes in ocean chemistry.
Oral Mini-Symposium 1: Lessons From the Past
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Photosymbiosis is a Major Theme in the History of Mesozoic to Cenozoic Reef Systems
George STANLEY JR.* 1 , B. VAN DE SCHOOTBRUGGE 2
1 Paleontology Center, University of Montana, Missoula, MT, 2 Institute of Geosciences, Goethe
University Frankfurt, Frankfurt, Germany
Symbiotic partnerships between photosynthetic dinoflagellates (zooxanthellae) and corals
provide enhanced nutrition and calcification and partly explain the reef phenomenon. They
elucidate the success and failure of many reefs today and in the geologic past. Here, we review
the geologic record of 240 million years of hexacoral evolution. It reveals the origin of the
group from soft-bodied anemone-like ancestors of the Paleozoic, the first appearance of
calcifying scleractinians in Middle Triassic time, and their subsequent rise to dominance.
Middle Triassic corals did not diversify or move into roles of reef building until Late Triassic
time, some 14 ma later. The co-occurrence of these early scleractinians with the earliest
dinoflagellates represented by suessiacean cysts and their subsequent expansion into roles of
reef-building in the Late Triassic, coincides in space and time. Furthermore, stable isotopes
confirm photosymbiosis in Late Triassic (Carnian-Norian) corals. We propose that this was the
time of their coevolution with zooxanthellae. The end-Triassic mass extinction disrupted this
ecological relationship, and a lengthy Early Jurassic post-extinction recovery led to coral reefs
of the Middle to Late Jurassic. The Cretaceous records high diversity among corals but a
subordinate role relative to rudistid bivalves. This is best explained by differential responses to
climate warming, especially during the Late Cretaceous greenhouse time. The end-Cretaceous
mass extinction removed the last surviving rudistids. Zooxanthellate corals later resumed
dominance on Paleogene reefs. The coral expansion among Neogene reefs led to ecologically
modern coral reefs. The resilience of Miocene-Holocene corals in the face of major
oceanographic and climate change is explained by the ecological flexibility of the
zooxanthellae-coral symbiosis, especially the ability of corals to switch clades of zooxanthellae
in response to environmental change. This may not have been the case in older zooxanthellate
corals.
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Early Cenozoic Recovery Of Caribbean Reef Coral Communities
Thomas STEMANN* 1
1 Department of Geography and Geology, The University of the West indies, Kingston, Jamaica
There is some controversy over the extent to which the K-T extinctions affected coral reef
communities at global and regional scales. Recent collections from latest Maastrichtian
successions indicate that diverse Caribbean reef coral communities persisted up until the very
end of the Cretaceous. The fate of this reef fauna is unclear, however, because early Cenozoic
Caribbean reef corals are so poorly known.
The present study examines new collections of early Cenozoic corals from Jamaica that provide
insight into Caribbean reef communities immediately following the K-T boundary. Extensive
sampling from sites in three units in the Paleocene of eastern Jamaica yields an average of