Halimeda: paleontological record and palaeoenvironmental significance

Udoteacean algae, identical or related to Halimeda, have been recorded in shallow-marine carbonate rocks since Upper Triassic. About 30 species have been described, most of which occur in Lower Cretaceous shelf carbonates. These species are conventionally attributed to four “genera” (Arabicodium Elliott, Boueina Toula, Halimeda Lamouroux, Leckhamptonella Elliott), but the validity of these taxa is a matter of discussion (generic or subgeneric position, or synonyma of Halimeda?) owing to wide discrepancies in the classification of fossil and recent species of halimediform algae. The paleoenvironmental setting of the Mesozoic and the Tertiary is comparable with that of recent Halimeda: lagoonal as well as reefal environments are already known from Upper Triassic occurrences. A reinvestigation of Boueina limestones described from Norian-Rhaetian lagoonal carbonates of Western Thailand indicates the important role of the alga (Boueina marondei n. sp.) in sediment accumulation from its very beginnings.

     

Halimeda biomass,growth rates and sediment generation on reefs in the central great barrier reef province

The average biomass ofHalimeda per m² of solid substratum increased progressively on a series of reefs situated at increasing distances from the shore in the central Great Barrier Reef. There was none on a reef close inshore, increasing to nearly 500 g m^?2 total biomass (?90% calcium carbonate) on an oceanic atoll system in the Coral Sea. The biomass measured contained 13 species ofHalimeda but was dominated by only two species,H. copiosa andH. opuntia, except on the atoll whereH. minima was dominant. Three sand-dwelling species were also present but did not occur anywhere in substantial quantities. Growth rates of the dominant species were measured bv tagging individual branch tips. A mean value of 0.16 segments d^?1 was recorded but 41% of the branch tips did not grow any new segments whilst only 1% grew more than one per day. The number of branch tips per unit biomass was very constant and has been used in conjunction with growth rates and biomass to calculate productivity rates, and thence sedimentation, in the lagoon of one of the reefs. Biomass doubling time of 15 d and production of 6.9 g dry wt m^?2 d^?1 are considerably higher than previously reported values forHalimeda vegetation and there was little seasonal change detected over a whole year. Those values indicate annual accretion of 184.9 g m^?2 year^?1 ofHalimeda segment debris over the entire lagoon floor (5.9 km²) of Davies Reef, equivalent to 0.13 mm year^?1 due toHalimeda alone, or 1 m every 1,892 years when other contributions to that sediment are taken into account.     

Microbial deposits in upper Miocene carbonates, Mallorca, Spain

The Santanyí Limestone, a 30-35-m thick upper Miocene limestone succession cropping out in Mallorca, contains abundant microbialite deposits, the shape, microstructure and texture of which was controlled by environmental factors: depth, energy and salinity. Three main types of microbialites are distinguished: (1) domed (DNOS) and stratiform, mostly undulate (UNOS) non-oolitic stromatolites, (2) undulate oolitic laminites (UOL) and (3) domed-oolitic thrombolites (DOTs). Based on lithofacies associations and occurrence of microbialite types, the Santanyí Limestone succession is subdivided into five stratigraphic units (I to V) separated by sharp surfaces. Within units II, III and V, the vertical evolution of microbialites was induced by changes in accommodation space/depth: (1) intertidal/very-shallow subtidal conditions at the base were induced by flooding over a wide area, (2) continued sea-level rise caused submergence to subtidal conditions, and (3) a significant bathymetric decrease created the sharp surface bounding these units.In units II and III, NOS accumulated in variable energy and depth conditions, as buildups with thick, somewhat discontinuous and mostly non-isopachous lamination, surrounded by oolitic grainstones with wave and current structures and oolitic intraclasts. In contrast, thin and generally regular and smooth lamination of NOS in unit V suggests, along with the absence of oolite grainstones and macrobiota, calm and restricted, maybe more saline, conditions.UOL, consisting of oolitic layers separated by thin micritic laminae, developed adjacent to NOS in units II and III and to DOT at the lower part of unit III, in shallow-water and low-energy conditions. Both ooids and micrite laminae have evidence for biogenesis. Micritized ooids containing microbial remains are common. Micritic laminae in UOL and the dark micritic laminae in NOS are thought to represent bacterially enhanced calcite precipitation and lithification during periods of low sedimentation.Oolitic thrombolites containing macrobiota are only present in unit III. They represent deeper and open-marine conditions affected by high-energy events, in which microbially mediated precipitation favoured microbialite accretion and lithification.     

The diversity and paleoenvironmental significance of Calophyllum (Clusiaceae) from the Miocene of southeastern China

Abstract

Three species within the genus Calophyllum collected from middle Miocene Fotan Group sediments in Zhangpu County, Fujian, southeastern China are described in this paper. These fossils include Calophyllum zhangpuensis sp. nov., Calophyllum striatum, and Calophyllum suraikholaensis. The new fossil species C. zhangpuensis sp. nov. is oval, possesses entire leaves with closely spaced parallel secondary veins and has a round, or slightly retuse, apex. These specimens represent the first known fossil records of this relative wide leaf-type form of Calophyllum from China and have a length:width (L:W) ratio less than 3:1. In combination with the known modern geographic distribution and habitats of this wide leaf-type Calophyllum and other plants, data suggest that the middle Miocene Fotan flora is indicative of a warm climate. Thus, based on available fossil data, we speculate that this genus probably originated in India during the Paleocene before spreading from India to Bangladesh and into China, Sumatra, Malaysia, Indonesia, and Java during the Neogene, leading to its modern distribution. At least, the 3 fossil species in this region can explain floristic exchange between India, Fujian, and South China, which is consistent with previous studies; the occurrence of these 3 species indicates that Calophyllum began to diversity in China no later than the Miocene.     

Comparison of deep-water coral reefs and lithoherms off southeastern USA

Two types of deep-water coral bioherms occur off the coast of southeastern United States: Oculina and Lophelia/Enallopsammia. The deep-water Oculina bioherms form an extensive reef system at depths of 70–100 m along the shelf edge off central eastern Florida. These reefs are comprised of numerous pinnacles and ridges, 3–35 m in height. Each pinnacle is a bank of unconsolidated sediment and coral debris that is capped on the slopes and crest with living and dead colonies of Oculina varicosa, the ivory tree coral. In comparison, deep-water reefs of Lophelia pertusa and Enallopsammia profunda corals occur at depths of 500–850 m (maximum 150-m relief) along the base of the Florida-Hatteras slope in the Straits of Florida. On the western edge of the Blake Plateau off South Carolina and Georgia, 54-m high banks of Enallopsammia and Lophelia occur at depths of 490–550 m, whereas on the eastern edge of the plateau the reefs form structures 146 m in height and at depths of 640–869 m. The geomorphology and functional structure of both the Oculina and Lophelia reefs are similar. North of Little Bahama Bank, at depths of 1000–1300 m, a region of bioherms is dominated by the coral Solenosmilia sp.; Lophelia is reportedly absent. This paper summarizes 25 years of submersible studies on the deep-water Oculina reefs, describes submersible reconnaissance of deep-water Lophelia reefs off the southeastern United States, and contrasts these types of bioherms with the deep-water lithoherms in the Straits of Florida west of the Bahamas.     

Lacustrine sedimentation in the diapir-controlled Miocene Bicorb Basin, eastern Spain

The Miocene Bicorb Basin is a small elongated basin developed by normal faulting of a thick Jurassic–Cretaceous carbonate succession and subsequent diapirism of Upper Triassic mudstones and evaporites. The basin fill comprises a sequence over 650 m thick formed by two units. The lower, alluvial unit consists of a complex alternation of conglomerates, sandstones, mudstones, and minor lacustrine limestones. The upper unit comprises marginal alluvial and lacustrine deposits in which seven lacustrine facies associations have been distinguished. The inner lacustrine deposits comprise mudstones and carbonates with minor evaporitic deposits. At the northeast and southwest basin edges, alluvial inputs led to the development of delta and fan-delta environments where sandstone and conglomerate deposits dominate. The latter stages of the lake evolution are represented by an expansive thick limestone sequence which close to the NW fault-bounded margin pass laterally to breccias. The hierarchical arrangement of the upper unit shows five different orders of sequences. The first-order sequence defines a major vertical trend of lake expansion whereas three second-order sequences are linked to major flooding-expansion episodes. All these sequences are related to the tectonic evolution of the diapir. Metre-scale, third- and fourth-order sequences and fifth-order sequences, which consist of finely laminated rhythmite deposits probably record climatically forced processes. The diapir–graben system evolution and the climatic variations have exerted major controls on the sequential arrangement and evolution of the lacustrine system. Both factors have also strongly influenced the changes in the gastropod assemblages.     

Evolution and phylogeography of Halimeda section Halimeda (Bryopsidales, Chlorophyta)

Nuclear ribosomal and plastid DNA sequences of specimens belonging to section Halimeda of the pantropical green seaweed genus Halimeda show that the group under scrutiny contains many more genetically delineable species than those recognized by classical taxonomy. Discordances between phylograms inferred from nuclear and plastid DNA sequences suggest that reticulate evolution has been involved in speciation within the clade. Nonetheless, our data do not allow ruling out certain alternative explanations for the discordances. Several pseudo-cryptic species are restricted to the margins of the generic distribution range. In a clade of H. cuneata sibling species from widely separated subtropical localities in the Indian Ocean, the South African sibling branches off first, leaving the Arabian and West Australian species as closest relatives. We hypothesize that geographic isolation of the siblings may have taken place following Pleistocene or Pliocene periods of climatic cooling during which subtropical species occupied larger distribution ranges. A more basal separation of Atlantic, Indo-Pacific, and Mediterranean species indicates vicariance. The alternative events that could have caused this vicariance are discussed.     

Nocardia in soils of southeastern Spain: abundance, distribution, and chemical characterisation

Actinomycetes belonging to the genus Nocardia were isolated from the surface horizon of 15 out of 46 soil samples examined. All the nocardiae strains isolated contained mycolic acids and saturated and unsaturated straight chain fatty acids (from 12 to 18 carbon atoms) and tuberculostearic acid and were biochemically identified as members of the Nocardia asteroides complex. Nocardiae were detected in alluvial, brown, and serosem great soil groups, but not in calcic brown, solontchack, and regosol great soil groups. Numbers of nocardiae isolated varied from 5.12 X 10(2) to 1.21 X 10(4) colony-forming units per gram of dry weight, and they were statistically correlated with the carbon content (percent C) of the soil. Soil samples were, in general, very dry.     

Miocene ostracods of Chuya and Kurai depressions of the southeastern Altai

Ostracods from the lacustrine–alluvial beds of intermontane troughs of the Altai Mountains are examined. Ostracods similar in species composition are recorded in the Lower–Middle Miocene of southeastern Kazakhstan. Changes in species composition and abundance of ostracods in the section of boreholes caused by changes in paleogeographical conditions of water bodies are analyzed. A new species of the genus Candona is described. For the previously known ostracod species, figures are provided.     

Coral successions in Upper Tortonian reefs in SE Spain

Martin, Jose M., Braga, Juan C. & Rivas, Pascual 1989 07 15: Coral successions in Upper Tortonian reefs in SE Spain. Lethaia , Vol. 22, pp. 271–286. oslo. ISSN 0024–1164,
During the Upper Tortonian (Upper Miocene), the Almanzora river corridor, a small Neogene basin in SE Spain, harboured coral reefs growing in three different environments: in fan deltas, beyond the influence of coarse terrigenous sedimentation; in the abandoned lobes of a delta complex; and on coastal margins. All of these reefs are composed of several successive beds, each of which may be made up mainly of Porites embedded in silt or of an initial Porites level followed by a silt-free Tarbellastraea level on top. Porites may be associated with corallines. This structure is interpreted as being the result of an ecological succession repeated over and over again. A pioneer association consisting mainly of Porites . by colonizing the substrate and continuing to grow through relatively adverse silt-deposition conditions, prepares the ground for Tarbellastraea to take over. A return to the previous conditions halts the growth of the Tarbellastraea colonies and the Porites association once more establishes itself in the silt, or else the renewed rate of deposition is sufficiently heavy to suffocate the whole bioconstruction.* Ecological succession. coral reefs, Tortonian, southeast Spain .     

New data on late Miocene mammals of Kohfidisch, Austria

Cervids and bovids of the Early Turolian mammalian fauna of Kohfidisch (Austria) are reviewed. A new species, Micromeryx mirus sp. nov. (Moschidae) is described.     

Zonation of late Miocene and early Pliocenecircum-mediterranean faunas

This attempt at biostratigraphic correlations for the fossiliferous sites of the late Miocene and early Pliocene,situated around the Mediterranean basin, is based on the zones established by P. Mein according to variations in the mammalian faunas. New taxa are mentioned, particularly carnivores; moreover, a series of African localities are integrated and, for some of them, an analysis of the faunal constituents leads to paleobiogeographic considerations.     

Changes of palaeozonation patterns within Miocene coral reefs, Gebel Abu Shaar, Gulf of Suez, Egypt

The Gebel Abu Shaar represents the southern end of a tilted fault-block consisting of Precambrian basement upon which a mixed siliciclastic-carbonate platform developed during mid-Miocene time. The Miocene sequence contains coral reefs and reef facies. Palaeozonation patterns of the Miocene coral reefs were assessed on the well-preserved outcrops of the Gebel Abu Shaar by recording both qualitative and quantitative data of reef-building assemblages. The various patterns of palaeozonation were analysed and compared at different spatial and temporal scales, including both within-reef and between-reef variations. The palaeozonal changes recorded within these fossil reefs are similar to those described from present-day living coral reefs and involve contraction or extension, fusion or splitting, replacement and omission of reef-builder zones. Depending on the scale concerned, the nature and importance of changes affecting the palaeozonation pattern vary. Spatial variations of the palaeozonal pattern appear mainly controlled by local changes of ecological conditions while temporal variations are related to regional and global environmental changes.     

Serum zinc levels in healthy subjects from southeastern Spain

The serum zinc (Zn) concentrations of 80 healthy subjects (48 male, 32 female) from southeastern Spain were determined by atomic absorption spectrometry. The samples were digested by heating in a 4:1 mixture of nitric and perchloric acids. The concentration of Zn was determined against a Contox Trace Metal Serum Control Panel A standard reference. Zn concentrations in the standard were found to be 2.332 ±0.489 mg/L, with a mean recovery of 102.7%. In the serum samples, the relative standard deviation was <6% for the range of concentrations determined: 0.420-1.540 mg/L for women (mean value 0.947 ±0.265 mg/L) and 0.490-1.480 mg/L for men (mean value 0.951 ±0.243 mg/L). In healthy subjects, no statistically significant differences were observed in the Zn levels with respect to their sex (p > 0.05) or the location where they lived (mountainous vs coastal zones). It is concluded that the dietary Zn intake and Zn status for healthy adults in this region of Spain are within normal values.