Carbonate Rubble Research Articles

Pulse sediment event does not impact the metabolism of a mixed coral reef community

Sedimentation can bury corals, cause physical abrasion, and alter both spectral intensity and quality; however, few studies have quantified the effects of sedimentation on coral reef metabolism in the context of episodic sedimentation events. Here, we present the first study to measure coral community metabolism - calcification and photosynthesis - in a manipulative mesocosm experiment simulating a pulse sediment event. We exposed a mixed benthic community composed of 75% live carbonate rubble cover and 25% Montipora capitata coral cover to an approximately 275 mg cm−1 (sediment accumulation) acute pulse sediment loading event. No differences were found in net calcification or net photosynthesis between the control and treated mesocosms 48 h and 25 d following exposure to pulse sediment input. Results from this community experiment indicate the ability of Montipora capitata, a common reef coral, to persist under these acute sediment levels, demonstrating resistance to episodic sediment events.

Flooding a landscape: impact of Holocene transgression on coastal sedimentology and underwater archaeology in Kiladha Bay (Greece)

Franchthi Cave, bordering Kiladha Bay, in Greece, is a key archaeological site, due to its long occupation time, from ~ 40,000 to ~ 5000 year BP. To date, no clear evidence of Neolithic human dwellings in the cave was found, supporting the assumption that Neolithic people may have built a village where there is now Kiladha Bay. During the Neolithic period/Early Holocene, wide areas of the bay were indeed emerged above sea level. Bathymetric and seismic data identified a terrace incised by a valley in ~ 1 to 2 m sediment depth. Eight sediment cores, up to 6.3-m-long, were retrieved and analysed using petrophysical, sedimentological, geochemical, and chronostratigraphic methods. The longest core extends into the exposure surface, consisting of a layer of carbonate rubble in a finer matrix, representing weathering processes. Dated organic remains place this unit at ~ 8500 cal year BP. It is overlain by stiff silty mud representing an estuarine environment. This mud is capped by reduced sediments with roots marking an exposure surface. A shell-layer, dated to ~ 6300 cal year BP, overlies this terrestrial sequence, reflecting the marine transgression. This layer occurs at 10.8 mbsl, 7.7 m deeper than the global sea level at that time, suggesting tectonic subsidence in the area. It is overlain by finer-grained marine carbonate-rich sediments. The top of the core shows traces of eutrophication, pebbles and marine shells, all likely a result of modern anthropogenic processes. These results are interpreted in the context of human occupation: the exposed surface contains pottery sherds, one dating to the Early to Middle Neolithic period, indicating that Neolithic people were present in this dynamic landscape interacting with a migrating coastline. Even if the artefacts are isolated, future investigations of the submerged landscape off Franchthi Cave might lead to the discovery of a Neolithic village, which eventually became buried under marine sediments.

ECOLOGICAL ENGINEERING CONSIDERATIONS FOR CORAL REEFS IN THE DESIGN OF MULTIFUNCTIONAL COASTAL STRUCTURES

A multifunctional structure is being designed for the Kahului Harbor, Maui, Hawai‘i, to mitigate operational problems caused by wave energy while also providing coral reef habitat. There is limited information on how the design of a coastal structure can be manipulated to enhance the ecology of targeted coral communities. To inform the ecological engineering of an artificial coral reef, the relationship between substrate characteristics and coral colonization was investigated through coral recruitment experiments and study of field conditions. Three concrete compositions that differed by the use of basalt, limestone, or recycled aggregates were tested in field and laboratory experiments to determine the impact of each substrate on the recruitment of juvenile hermatypic corals. The concrete test plates were deployed in three environments for a period of about one year, after which the coral recruits on each plate were identified and counted. No significant difference was found in the average number of coral recruits on the concrete mixed with basalt, limestone and recycled aggregate (60 ± 9, 83 ± 17 and 77 ± 14, respectively). Significant differences in coral recruitment were found due to the laboratory tanks, deep water, and shallow water field tests environments (86 ± 11, 135 ± 15 and 4 ± 1, respectively). These results highlight the importance of environmental site conditions for the development of coral reef habitat. A field study was conducted in the vicinity of purposed artificial reef site to relate the topographic features of the surrounding environment to the levels of live coral coverage. The benthic zone was surveyed using a drop camera system and by divers who recorded in-situ observations. Of the area surveyed, the highest density of coral coverage (>90% cover on 60% of the area) was found on an adjacent natural reef area that was characterized by spur and groove geomorphology with a high degree of macro- and microtopographic complexity. In contrast, sparse coral cover was discovered on the concrete armor units of the existing east breakwater structure, while no live coral cover was observed on the sand and carbonate rubble substrate at the proposed artificial reef location. The high degree of coral coverage on the adjacent natural reef suggests that the artificial coral reef design should emulate the natural spur and groove structure with regards to topographic complexity on multiple scales, orientation with wave direction, and water depth.

Community structure comparisons of lower slope hydrocarbon seeps, northern Gulf of Mexico

Photographic sampling collected from ROV JASON III on randomized transects (generally 10 per site) was used to compare seven suspected hydrocarbon seeps on the lower continental slope at depths of 956 to 2330m. The study design focused on areas containing high-amplitude reflectance patterns in seismic returns from the bottom. Animal samples nested in these areas and high-resolution photographic mosaics permitted fine-scale description of the community components and their associations with each other. The transect results showed three types of chemosynthetic community: carbonate prone, brine pool prone, and low-density. These communities are characterized by, respectively, abundant carbonate rubble and tubeworm clusters, bacterial mats and brine pools, and relatively sparse chemosynthetic fauna that tended to be overlooked by the photographic survey plan. These differences were not clearly related to depth or longitude because the sites are at the opposite eastern and western extents of the project region. Photographic survey is a statistically reliable method for detecting the carbonate rubble and bacterial mat types of community, but may be unreliable for sparse or clustered fauna such as seep mussels. Photographic survey results provided relatively low taxonomic resolution, but were sufficient to distinguish statistical differences in the abundance of characteristic faunal groups, such as the Echinoidea and Gorgonacea, associated with hydrocarbon seeps. Initial studies of statistical power indicate that future photographic surveys of suspected seep communities, if conducted with an equivalent level of effort, might detect the presence of more abundant habitat, including carbonate rubble, bacterial mats, and tubeworms, but could miss less abundant indicators.

Substratum preferences in planula larvae of two species of scleractinian corals, Goniastrea retiformis and Stylaraea punctata

To test whether coral planulae recruit randomly to different coral reef habitats or have specific substratum preferences, the settling behavior of planulae from two shallow water coral species from Pago Bay, Guam (13°25.02N, 144°47.30E) were examined in the laboratory in June and July of 1995. Goniastrea retiformis is generally restricted to the shallow reef front (<10 m depth) in areas dominated by crustose coralline algae (CCA), while Stylaraea punctata is abundant on inner reef flats were CCA coverage is low and sand and carbonate rubble covered by biofilms is common. When presented with four substrata (1) carbonate rock scrubbed free of biofilm and dried as a control, (2) the CCA Hydrolithon reinboldii, (3) the CCA Peyssonelia sp., and (4) naturally conditioned carbonate rubble covered by a biofilm, G. retiformis larvae showed a significant preference for H. reinboldii, and S. punctata larvae for the carbonate biofilm treatment. The preference shown by S. punctata larvae for biofilmed surfaces did not diminish with increasing larval age up to 11 days. These results suggest that the larvae of both species are capable of habitat selection, and that the preferred substrata among those tested bears a relationship to the habitats in which adult colonies were found.

Benthic communities associated with carbonate rubble and adjacent soft sediments in a shallow coastal area of O'ahu, Hawai'i

Benthic communities associated with carbonate rubble and adjacent soft sediments in a shallow coastal area of O'ahu, Hawai'i

Mapping of the Biological Resources of the Continental Shelf

Distribution patterns of the penaeid shrimp and demersal fish species are discussed based upon collections totaling in excess of 330,000 shrimp and 2,245,000 fishes. Depth related zonation reveals nearshore, mid-shelf, outer shelf, and trans-shelf assemblages. Estuary related species are particularly prominent on the northwestern Gulf shelf, while rock and reef related species are most important in the fauna of the eastern Gulf shelf. Recognizable elements in the shelf fauna also include species of tropical affinity; open ocean and upper slope species; inhabitants of seagrass beds, mangrove swamps, and carbonate rubble and shell hash; burrowers in soft bottoms; and inhabitants of the upper water column. The eastern Gulf shelf is inhabited by twice as many fish species and eight times as many unique species as the northwestern shelf, reflecting the great diversity of habitat types in the eastern Gulf. A few key species numerically dominate the ichthyofauna of the northwestern shelf, but dominance is spread through many species in the east. Seasonal shifts in species density primarily reflect inshore/offshore seasonal migrations of estuary related species, but seasonal inshore/offshore density shifts are also observed among the true shelf residents. Trophically the shelf systems are supported by precipitated plankton and organic detritus derived from rivers, bays and estuaries, seagrass beds, and mangrove swamps, although attached algae are also important producers in the east. Mollusks, polychaetes, and small crustaceans which feed upon this material, in turn, support the demersal fish communities whose species are generally short-lived. Larger longlived predators are mostly seasonal migrants which appear in the northern Gulf during the warmer months. Bottom-feeding generalists are prominent in the northwest, while specialists are in great evidence in the east. These distributional studies lay the foundation for understanding the shelf ecological systems, and they also provide a basis for informed management decisions.

Hydrates, oil seepage, and chemosynthetic ecosystems on the Gulf of Mexico slope

The northern Gulf of Mexico continental slope has been the site of a number of recent discoveries that may dramatically alter our understanding of biological and chemical processes on the continental slope. The Geochemical and Environmental Research Group at Texas A&amp;M University reported in Science last year (vol. 225, p. 409, 1984) the first occurrence of thermogenic gas hydrates in deep ocean sediments. The hydrate discovery sites were located at water depths of 530‐560 m on the Louisiana slope. These hydrates, obtained by piston coring, ranged in size from minute crystals to objects several centimeters in diameter and were composed of methane through butane hydrocarbon gases. The hydrates were often dispersed in carbonate rubble within the cores and were distributed from the top of the core to a sediment depth of at least several meters.

Massive Siliciclastic Deposits Juxtaposed Against Massive Carbonate Bodies: Paradox of Eastern Gulf of Mexico: ABSTRACT

The eastern Gulf of Mexico is the location of a major and dramatic transition from siliciclastic to carbonate deposits and deposition. The massive lutites that make the Mississippi Cone are juxtaposed against the equally massive carbonates intercalated with evaporites that make the western portion of the Florida Platform. The region now occupied by the continental margin of the eastern Gulf has been cut off from clastic sedimentation since Late Jurassic or Early Cretaceous time, and over 5,000 m (16,404 ft) of predominantly carbonate sediments have built up. Surficial sediments of the carbonate portion of the transition zone are called the West Florida Lime Mud Facies. A foraminifera-coccolith ooze is still being deposited in water depths as shallow as 200 m (656 ft); this facies covers over 40,000 km2 (15,444 mi2) and in many respects resembles a deep-sea ooze. However, in some places shelf carbonate debris, including whole valves of mid-shelf oysters, have cascaded over the shelf-slope break and are incorporated into the slope ooze. Composition, rates of accumulation, and relatively shallow deposition suggest that this sedimentary body may be an analog of some of the chalk deposits of northwestern Europe. It has long been considered axiomatic that planktonic foraminifera and coccolith oozes are deep-sea deposits that accumulate at rates of a few tens of millimeters per thousand years. However, radiocarbon dates show that the eastern Gulf margin ooze has accumulated rapidly. Prior to the last rise in sea level, deposition rates were as high as 65 cm/1,000 years (25 in./1,000 years); and ever since sea level began to rise sedimentation rates have still been as high as 20 cm/1,000 years (8 in./1,000 years). Such a rapid buildup of the carbonate sediments has led to widespread mass wasting and all forms, from creep to massive multiple slide deposits containing thousands of cubic kilometers of material, are represented in our set of high resolution seismic profiles. The actual contact between carbonates and siliciclastics occurs in a variety of styles. Carbonate rubble is found in a terrigenous lutite matrix at the base of the West Florida Escarpment. Farther west on the Mississippi Cone the brown and yellow-brown siliceous lutites contain carbonate turbidites with provenance the West Florida slope. Another type of contact is shown in some piston cores with carbonate ooze in normal and alternating depositional End_Page 453------------------------------ contact with Mississippi siliceous lutite. The position and timing of alternating carbonate and fine terrigenous deposition, as well as the loci of carbonate buildups on the slope, must be affected and perhaps even controlled by the positioning of the Loop Current, a major precursor to the Gulf Stream which, depending upon factors as yet not totally understood, irregularly advances into or retreats from the eastern Gulf. When the loop is up and sweeps from north to south along the West Florida slope, it blocks or deflects Mississippi sedimentation. When the loop is restricted to the area of the Florida Straits, fines derived from the Mississippi River can be deposited at the base of the escarpment and even on the slope. End_of_Article - Last_Page 454------------

Life History, Growth Habits, And Constructional Roles of Acropora Cervicornis in the Patch Reef Environment

ABSTRACT In two representative patch reefs within the Florida Reef Tract the majority of Acropora cervicornis colonies appear to have developed from broken fragments of parent colonies rather than directly from settled larvae. Following breakage, both the parent and the fragment regenerate polyps to cover the broken area and apical polyps to continue growth (the parent appears to recover more quickly). Fragments first attach to the substrate by growing laterally, thereby forming a stabilizing base. They then begin to grow upward. Two main morphological growth forms result from this process: (1) Forms which result from branches of the colony fusing with other branches of the colony; and (2) Forms which result from the interaction of the branches of the colony with the surrounding substrate and organisms. Branches of A. cervicornis may grow parallel or cross closely without fusing. However, most branches fuse on contact, with polyps covering the contact area. On the reefs examined, the A. cervicornis colonies were small, relatively scattered, and did not appear to be a major binding agent. However, within the immediate vicinity of the colonies, they actively bind carbonate rubble and other clastic sediment. Thus in reefs where A. cervicornis is more abundant, this coral could be a major factor in fortification and stabilization. Intergrowth and attachment habits of A. cervicornis are compatible with its occurrence and morphology in many horizons of the Key Largo Limestone, generally interpreted to be a Pleistocene equivalent of the present day Florida patch reefs.

Depositional and Non-Depositional Carbonate Breccias, Chiantla Quadrangle, Guatemala

Research Article| March 01, 1969 Depositional and Non-Depositional Carbonate Breccias, Chiantla Quadrangle, Guatemala DON N BLOUNT; DON N BLOUNT Research Department, Union Oil Company of California, Brea, California * Don N. Blount was killed on May 6, 1968 during a field excursion in eastern Mexico prior to completion of this paper. It is hoped that the final product adequately expresses the views of this exceptional young geologist. Search for other works by this author on: GSW Google Scholar CLYDE H MOORE, JR CLYDE H MOORE, JR Department of Geology, Louisiana State University, Baton Rouge, Louisiana Search for other works by this author on: GSW Google Scholar Author and Article Information DON N BLOUNT * Don N. Blount was killed on May 6, 1968 during a field excursion in eastern Mexico prior to completion of this paper. It is hoped that the final product adequately expresses the views of this exceptional young geologist. Research Department, Union Oil Company of California, Brea, California CLYDE H MOORE, JR Department of Geology, Louisiana State University, Baton Rouge, Louisiana Publisher: Geological Society of America Received: 23 Jul 1968 Revision Received: 13 Sep 1968 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1969, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1969) 80 (3): 429–442. https://doi.org/10.1130/0016-7606(1969)80[429:DANCBC]2.0.CO;2 Article history Received: 23 Jul 1968 Revision Received: 13 Sep 1968 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation DON N BLOUNT, CLYDE H MOORE; Depositional and Non-Depositional Carbonate Breccias, Chiantla Quadrangle, Guatemala. GSA Bulletin 1969;; 80 (3): 429–442. doi: https://doi.org/10.1130/0016-7606(1969)80[429:DANCBC]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Five types of carbonate breccia are recognized in the Chiantla quadrangle of northwestern Guatemala. Depositional breccias and conglomerates (lithoclastic limestones) are widespread in the Cretaceous Ixcoy limestone and attain thicknesses up to 500 m. The lithoclasts were eroded from adjacent emergent areas, which probably resulted from faulting. Depositional breccias are recognized by the presence of primary sedimentary structures, original lime-mud matrix, and polymictic clasts.A thick sequence (250 m) of evaporite-solution-collapse breccias is present in the lower part of the Ixcoy. These breccias are characterized by dolomite clasts in a matrix of sparry calcite and granulated dolomite. This breccia type is recognized primarily by its close relationship to thick evaporites in the subsurface and neighboring surface exposures. Secondary criteria for their recognition include dedolomite and dedolomitization textures and clasts composed of lithologies compatible with evaporite deposits.Tectonic breccias are formed by extensive fracturing of carbonates during periods of deformation. This breccia type is identified by its proximity to faults; its matrix of either coarse-crystalline, sparry calcite or granulated carbonate material; and oligomictic clasts with matching edges.Caliche breccias have formed by caliche cementation of carbonate rubble at the base of slopes, and by the development of caliche veins transecting dolomitic rocks.Pseudobreccias, which form by selective grain growth, occur locally in limestones of the Ixcoy. They are distinguished by similarity in lithology between “clasts” and “matrix,” highly irregular “clast”-shapes, and by a complete graduation in grain size from micrite in the “clasts” to sparry calcite in the “matrix.”These breccias, though similar in the field, may be distinguished by a combination of stratigraphic and petrographic criteria. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Experience gained in the operation of the V. I. Lenin Volga hydroelectric station

1. The hydraulic structures of the V. I. Lenin Volga hydroelectric power station, built on Tertiary clays and alluvial soils, have operated normally for 12 years. 2. The concrete and reinforced concrete of carbonate rubble from local quarries works well in the abovewater and underwater massive elements of the hydraulic and industrial structures, and in the slope revements. 3. Rusting of the reinforcement is occurring for still unexplained reasons in the precast reinforced concrete (in the slabs and bearing beams of the roof of the power plant exposed to the air). 4. Effective means of protecting the metal structures against corrosion have been developed and are under-going long service testing: durable organic coating of perchloride and ethynyl varnishes and electrochemical (cathodic) protection combined with originally applied coatings.