11th ICRS Abstract book - Nova Southeastern University
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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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1.7 Microboring And Surface Taphonomy Of Fossil Reefs, Enriquillo Valley, Dominican Republic Benjamin TITUS* 1 , Halard LESCINSKY 1 1 Department of Life and Earth Sciences, Otterbein College, Westerville, OH Paleoecologists have several metrics for distinguishing ecological information from postmortem history (taphonomy), but it has been difficult to calibrate these with metrics used in ecological studies. Here we use microboring patterns to calibrate taphogrades in the Holocene reefs of the Enriquillo Valley, Dominican Republic. Pioneer microborers become established on newly exposed coral substrates by two weeks, and are then substantially replaced by other species within 3 months. Thus post-mortem exposure can be closely estimated using microboring abundance, depth, and type. Surface microboring also determines how “pristine” a fossil looks and hence its taphonomic grade. A correlation between the two measures was examined along two 125m transects on an exposed reef at Cañada Honda. Each coral was assigned a taphograde on a 1 to 6 scale (1 is pristine) and examples of each taphograde were then randomly selected and returned to the lab for analysis. Coral samples were cut, impregnated with epoxy-resin, etched, and examined under the S.E.M. for microborers. Microboring intensity was quantified at .5mm intervals perpendicular to the coral surface using Image analysis software. Taphograde assignments and microboring intensity were closely related. Grade 1 corals had no microboring indicating post mortem exposure of

Poster Mini-Symposium 2: Biotic Response to Ancient Environmental Change in Indo-Pacific Coral Reefs 2.28 Coralline Algae in Messinian (Upper Miocene) Mediterranean Reefs Juan C. BRAGA* 1 , Alessandro VESCOGNI 2 , Francesca BOSELLINI 3 , Julio AGUIRRE 1 1 Estratigrafia y Paleontologia, Universidad de Granada, Granada, Spain, 2 Scienze della Terra, Universita di Modena e Reggio Emilia, Modena, Italy, 3 Scienze della Terra, Universita di Modena e Reggio Emilia, Modeba, Italy The last reefs built by zooxanthellate corals in the Mediterranean region thrived during the Messinian (7.2 to 5.3 Ma, Late Miocene). Porites is almost the only reef-building coral and only a few colonies of Siderastrea and Tarbellastraea have been recorded. Coralline red algae are secondary reef builders, together with encrusting foraminifers and microbial micritic crusts. The study of coralline algae from the Messinian reefs of the Salento Peninsula (southern Italy) and of the Sorbas and Almería basins (southeastern Spain) reveals coralline assemblages that are substantially different from their coeval low-latitude counterparts. In all studied sites, these coralline assemblages show palaeodepth-related distribution. Shallow-water corallines mainly occur as plants encrusting coral colonies and their assemblages are dominated by Neogoniolithon, Spongites, and Lithophyllum species. Deeper-water corallines occur as rhodoliths (algal nodules) and crusts on bioclasts dominated by Lithothamnion and Phymatolithon, with minor Sporolithon and Mesophyllum. Although the most common species, N. brassicaflorida and a few other components, have been reported from tropical reefs, the Messinian coralline assemblages in the Mediterranean lack the main building corallines in Upper Miocene reefs in tropical latitudes—namely thick Hydrolithon species. Moreover, most of the recorded species lived or are still living in the Mediterranean Sea and the Atlantic coast of Europe. This species composition probably reflects the isolation of the Mediterranean Basin from the Indo-Pacific area since the Middle Miocene and the general cooling of the Mediterranean region throughout the Miocene. 2.29 Lower Miocene Submerged Reefs On The Koko Seamount David A. CLAGUE 1 , Juan C. BRAGA* 2 , Jody M. WEBSTER 3 , Davide BASSI 4 , Willen RENEMA 5 1 Monterey Bay Aquarium Research Institute, Moss Landing, CA, 2 Estratigrafia y Paleontologia, Universidad de Granada, Granada, Spain, 3 School of Earth and Environmental Sciences, James Cook University, Townsville, Australia, 4 Scienze della Terra, Universita di Ferrara, Ferrara, Italy, 5 Nationaal Natuurhistorisch Museum, Leiden, Netherlands Koko Seamount is in the southern part of the Emperor seamounts near the bend of the Hawaiian-Emperor chain, in the northern Pacific basin. Radiometric (40Ar/39Ar) ages of shield and postshield volcanism in the seamount range from 52.6 to 50.4 Ma (Early Eocene) (Sharp & Clague, 2006). Dredged carbonate samples from the top of the seamount reveal the occurrence of Lower Miocene coral reefs and associated deposits. Porites and several faviid genera encrusted by coralline algae (Hydrolithon?) represent the shallowest facies recorded. Packstones of Amphistegina with minor coralline algae probably formed at intermediate depths according to depth distribution of modern analogs. Packstones to floatstones with lepidocyclines, bryozoans, and coralline red algae nodules (mainly made up of Lithothamnion and Sporolithon) accumulated in the deepest settings of the carbonate platform that developed on the volcanic building. The recorded lepidocyclinids indicate an Early Miocene age for the carbonate deposits. The carbonate platform on the seamount now at about 500 m depth was drowned and remained submerged since that age. Sharp, W.D. & Clague, D.A. 50-Ma initiation of Hawaiian-Emperor bend records major change in Pacific plate motion. Science, 313, 1281-1284 2.30 Pattern of fossil coral communities from Ryukyu Island, Japan and Palau Islands during Holocene sea-level change Chuki HONGO* 1 , Hajime KAYANNE 1 1 Department of Earth and Planetary Science, The University of Tokyo, Tokyo, Japan Information of dynamics of coral communities following abrupt sea-level rise in Holocene is necessary to predict coral population responses to future sea-level rise. It is critical to understand on what time scale coral populations respond and whether communities and populations change in their formation to correspond to sea-level rise. Sedimentological and ecological analyses of boring cores from fringing reefs in Ishigaki Island, Ryukyu Islands and from a barrier reef in Palau Island have delineated different responses of fossil coral communities to the sea-level rise at their initial stage of reef development. Initiation timing of Holocene reef growth in Ishigaki and Palau Islands corresponded with each other around 8000 cal. years BP, however, coral communities were different between the two reefs. Holocene coral reefs in Ishigaki Islands were mainly composed shallow water coral communities (e.g. Acropora digitifera, A. hyacinthus, Goniastrea retiformis, and Montastrea curta) between around 8000 cal. years BP and 4800 cal. years BP at a mean growth rate of 6.1 m/ 1000 years, whereas Holocene coral communities of Palau Islands changed from Porites spp. in turbidity environment to arborescent coral communities (e.g. Acropora formosa and A. nobilis) after around 8000 cal. years BP until 7200 cal. years BP, and then uppermost coral reef of the islands consisted of shallow water coral communities (e.g. Acropora digitifera, A. robusta, and A. danai). It assumed that the difference in pattern of communities and populations depended on the initial wave condition related to wave directions and the type of initial coral population. It is clear that coral communities of the islands could survive the past sea-level rise, and also, it is essential to research on communities, population dynamics and environmental conditions in present coral reefs for projections of sea level rise in the future. 2.31 Shallow Seismic Profiling Survey On Holocene Coral Reefs Near The Present-Day Northern Limit Of Coral Reef Formation in The Northwestern Pacific Kohsaku ARAI* 1 , Takahiko INOUE 1 , Hiroki MATSUDA 2 , Hideaki MACHIYAMA 3 , Keiichi SASAKI 4 , Yasufumi IRYU 5 , Kaoru SUGIHARA 6 , Kazuhiko FUJITA 7 , Masakazu NARA 8 1 Geology and Geoinformation, Geological Survey of Japan, AIST, Tsukuba, Japan, 2 Department of Earth Science, Kumamoto University, Kumamoto, Japan, 3 Kochi Institute for Core Sample Research, JAMSTEC, Kochi, Japan, 4 Department of Cultural Properties & Heritage, Kanazawa Gakuin Unversity, Kanazawa, Japan, 5 Institute of Geology and Paleontology, Graduate School of Science, Tohoku University, Sendai, Japan, 6 Department of Earth System Science, Fukuoka University, Fukuoka, Japan, 7 Department of Physics and Earth Sciences, University of the Ryukyus, Nishihara, Japan, 8 Center for Marine Environmental Studies, Ehime University, Ehime, Japan Shallow seismic profiling survey, bathymetric mapping and ROV (remote operating vehicle) submersible observations were carried out to the east of northern Amami-o-shima Island (28°24’ N, 129°38’E). The survey area is located in a northern part of the Ryukyu Island Arc and close to the present-day northern limit of coral reef formation in the northwestern Pacific. This survey aims to delineate spatial distribution of modern coral reefs at a marginal region for a reef province and to unravel the factors controlling initiation of coral reefs during the last deglaciation. High-resolution seismic data were collected using AA300 Boomer Plate with 8 channels digital streamer cable. The survey lines in a direction for WNW to ESE ranged in length from 2 to 2.5 km, where water depth was 10 – 60 m. The interval of the lines was 100 m. Bathymetric surveys were conducted using a SeaBat 8101 multibeam echosounder along the seismic survey lines. The ROV video images and bathymetric map indicate that the eastern part of the survey area is characterized by presence of irregular-shaped mounds of modern coral reefs. In contrast, the flat seafloor, consisting mainly of coarse-grained, extends in the western area. Distinct, randomly undulated reflector which may represent erosional surface formed in the last glacial period is recognized throughout the survey area. The Holocene stratified sediment overlies this reflector; their thickness decrease eastward. The grooves which may correspond to eroded valleys formed during the last glacial period are found in the western margin of the eastern part of the survey area where the irregularly-shaped mounds occur. These results indicate that the coarse-grained sediment transported from Amami-o-shima Island has been trapped into grooves and that limited transportation of sediments into the eastern part may have allowed coral reef formation in this area during the last deglaciation. 268

1.7<br />

Microboring And Surface Taphonomy Of Fossil Reefs, Enriquillo Valley,<br />

Dominican Republic<br />

Benjamin TITUS* 1 , Halard LESCINSKY 1<br />

1 Department of Life and Earth Sciences, Otterbein College, Westerville, OH<br />

Paleoecologists have several metrics for distinguishing ecological information from postmortem<br />

history (taphonomy), but it has been difficult to calibrate these with metrics used<br />

in ecological studies. Here we use microboring patterns to calibrate taphogrades in the<br />

Holocene reefs of the Enriquillo Valley, Dominican Republic. Pioneer microborers<br />

become established on newly exposed coral substrates by two weeks, and are then<br />

substantially replaced by other species within 3 months. Thus post-mortem exposure can<br />

be closely estimated using microboring abundance, depth, and type. Surface microboring<br />

also determines how “pristine” a fossil looks and hence its taphonomic grade. A<br />

correlation between the two measures was examined along two 125m transects on an<br />

exposed reef at Cañada Honda. Each coral was assigned a taphograde on a 1 to 6 scale (1<br />

is pristine) and examples of each taphograde were then randomly selected and returned to<br />

the lab for analysis. Coral samples were cut, impregnated with epoxy-resin, etched, and<br />

examined under the S.E.M. for microborers. Microboring intensity was quantified at<br />

.5mm intervals perpendicular to the coral surface using Image analysis software.<br />

Taphograde assignments and microboring intensity were closely related. Grade 1 corals<br />

had no microboring indicating post mortem exposure of

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