Sedimentary evolution of a Late Pleistocene temperate red algal reef (Coralligène) on Rhodes,Greece: correlation with global sea‐level fluctuations     

JÜRGEN TITSCHACK  CAMPBELL S. NELSON  TIM BECK  ANDRÉ FREIWALD  ULRICH RADTKE 《Sedimentology》2008,55(6):1747-1776

Autochthonous red algal structures known as coralligène de plateau occur in the modern warm‐temperate Mediterranean Sea at water depths from 20 to 120 m, but fossil counterparts are not so well‐known. This study describes, from an uplifted coastal section at Plimiri on the island of Rhodes, a 450 m long by 10 m thick Late Pleistocene red algal reef (Coralligène Facies), interpreted as being a coralligène de plateau, and its associated deposits. The Coralligène Facies, constructed mainly by Lithophyllum and Titanoderma, sits unconformably upon the Plio‐Pleistocene Rhodes Formation and is overlain by a Maerl Facies (2 m), a Mixed Siliciclastic‐Carbonate Facies (0·2 m) and an Aeolian Sand Facies (2·5 m). The three calcareous facies, of Heterozoan character, are correlated with established members in the Lindos Acropolis Formation in the north of the island, while the aeolian facies is assigned to the new Plimiri Aeolianite Formation. The palaeoenvironmental and genetic‐stratigraphic interpretations of these mixed siliciclastic‐carbonate temperate water deposits involved consideration of certain characteristics associated with siliciclastic shelf and tropical carbonate shelf models, such as vertical grain‐size trends and the stratigraphic position of zooxanthellate coral growths. Integration of these results with electron spin resonance dates of bivalve shells indicates that the Coralligène Facies was deposited during Marine Isotope Stage 6 to 5e transgressive event (ca 135 to 120 ka), in water depths of 20 to 50 m, and the overlying Maerl Facies was deposited during regression from Marine Isotope Stage 5e to 5d (ca 120 to 110 ka), at water depths of 25 to 40 m. The capping Aeolian Sand Facies, involving dual terrestrial subunits, is interpreted as having formed during each of the glacial intervals Marine Isotope Stages 4 (71 to 59 ka) and 2 (24 to 12 ka), with soil formation during the subsequent interglacial periods of Marine Isotope Stages 3 and 1, respectively. Accumulation rates of about 0·7 mm year^?1 are estimated for the Coralligène Facies and minimum accumulation rates of 0·2 mm year^?1 are estimated for the Maerl Facies. The existence of older red algal reefs in the Plimiri region during at least Marine Isotope Stages 7 (245 to 186 ka) and 9 (339 to 303 ka) is inferred from the occurrence of reworked coralligène‐type lithoclasts in the basal part of the section and from the electron spin resonance ages of transported bivalve shells.  相似文献   

Changes in the winter precipitation in Romania and its relation to the large-scale circulation   总被引：1，自引：0，他引：1  

ARISTITA BUSUIOC  HANS VON STORCH 《地球，A辑:动力气象学与海洋学》1996,48(4):538-552

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Production and stable isotopic composition of CO₂ in a soil near Bern, Switzerland   总被引：2，自引：0，他引：2  

ROLF HESTERBERG  ULRICH SIEGENTHALER 《Tellus. Series B, Chemical and physical meteorology》1991,43(2):197-205

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A large-scale meandering submarine canyon: outcrop example from the late Proterozoic Adelaide Geosyncline, South Australia     

C.C. VON DER  BORCH  A. E. GRADY  R. ALDAM  D. MILLER  R. NEUMANN  A. ROVIRA  K. EICKHOFF 《Sedimentology》1985,32(4):507-518

The late Proterozoic Adelaide Geosyncline, along with overlying Cambrian strata, comprises a thick sequence of sediments and sparse volcanics which accumulated in a major rift and passive margin setting. During late syn-rift or early post-rift phases, large volumes of terrigenous and carbonate sediments of the late Proterozoic Umberatana and Wilpena Groups and Cambrian Hawker Group filled the rift. Submarine canyon development was related to at least four of these depositional cycles, the most notable of which resulted in incision and subsequent filling of the major (several kilometres in width and up to 1.5 km deep) submarine canyons by the Wonoka Formation. The Wonoka Formation canyons are not obviously fault controlled. They are interpreted to have been eroded by turbidity currents during a relative low-stand of sea-level. They were subsequently filled by a fining-upwards suite of sediments which reflects subsequent relative rise of sea-level and carbonate platform development. Ultimately the canyon complex was buried by north-westerly progradation of overlying fluvial and slope sequences (Billy Springs Beds and possibly correlative upper Pound Subgroup). It is considered likely that more distal elements of this prograding clastic wedge provided the necessary material for canyon erosion, prior to canyon filling and ultimate burial by what may have been elements of the same depositional cycle. It is considered possible that the series of isolated outcrops of canyon cross-sections within the Wonoka Formation are sections of a single canyon thalweg developed within a considerably broader zone of slope degradation. If this interpretation is correct, then the gorge-like Patsy Springs Canyon lies in more proximal regions of the basin-slope, whereas 40 km to the north-east the lower slope is cut by the Fortress Hill Canyon Complex. Palaeocurrent analyses of channel-fill turbidites within the canyons imply that the Fortress Hill Complex is in fact the outcropping western edge of a sinuous, incised canyon thalweg. The Wonoka Formation canyons, containing basal sedimentary breccias but only minor conglomerates, are considered typical of passive margin canyon development. They are contrasted with the generally highly conglomeratic channel-fills observed in outcropping Tertiary and Cretaceous examples of active margin canyons and upper fan valleys.  相似文献   

Stable isotope study of carbonate sediments from the Coorong Area, South Australia     

REINER W. BOTZ†  CHRISTOPHER C. VON DER  BORCH† 《Sedimentology》1984,31(6):837-849

ABSTRACT
The mineralogy and isotope geochemistry of carbonate minerals in the Coorong area are determined by the water chemistry of different depositional environments ranging from seawater to evaporitically modified continental water. The different isotopic compositions of coexisting calcite and dolomite suggest that each of the above two minerals was formed from water of composition and origin unique to that specific mineral. In addition, the dolomite was not formed by simple solid state cation exchange.
The occurrence of two types of dolomite was shown by isotope analysis and SEM observations. The dolomite, which is isotopically light (δ¹³C = -1 to -2% 0 ; δ¹⁸O=+3 to +5%₀) and of fine grain size (˜ 0·5 μm) probably precipitated under the influence of evaporitically modified continental water. Coarser grained dolomite (up to 4 μm) is isotopically heavier (δ¹³C=+3 to +4%₀; δ¹⁸O=+5 to + 6%₀) contains Mg in excess of Ca and was formed in or close to equilibrium with atmospheric CO² probably by the dolomitization of aragonite.  相似文献   

The Zircon-Bearing Chromitites of the Phlogopite Peridotite of Finero (Ivrea Zone, Southern Alps): Evidence and Geochronology of a Metasomatized Mantle Slab   总被引：6，自引：0，他引：6  

GRIECO  G.; FERRARIO  A.; VON QUADT  A.; KOEPPEL  V.; MATHEZ  E. A. 《Journal of Petrology》2001,42(1):89-101

The phlogopite peridotite unit of the Finero Complex is a restiticharzburgite that records two metasomatic events. The first eventis related to the intrusion of basaltic magma, which reactedwith the pyroxene of the host harzburgite to produce chromititepods with dunite haloes. It also produced secondary clinopyroxeneand amphibole in the harzburgite and enriched harzburgite inNa and the light rare earth elements. The second metasomaticevent is related to the later intrusion of clinopyroxeniticdykes. During this event, water-rich vapour penetrated the harzburgitealong fractures and reacted with it to form phlogopite, thusenriching the rock in K. Chromitites host zircons that yieldan age for the first metasomatic event of 207·9 + 1·7/-1·3Ma, during which time extensional tectonics prevailed in theSouthern Alps. KEY WORDS: metasomatism; chromitite; zircon; geochronology; Finero  相似文献   

Comment on “The chemical variation of moldavite tektites: Simple mixing of terrestrial sediments” by Th. Meisel,J. M. Lange and U. Krähenbühl     

WOLF VON ENGELHARDT  J RG ARNDT 《Meteoritics & planetary science》1998,33(3):535-535

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Spherular modern dolomite from the Coorong area, South Australia   总被引：1，自引：0，他引：1  

C. C. VON DER  BORCH J. B. JONES 《Sedimentology》1976,23(4):587-591

Scanning electron micrographs show that the youngest and apparently least altered of the Coorong dolomite is in the form of spherular bodies about 0.2–1.0 μm in size which themselves are composed of spherules about 100 nm in diameter. Older and more lithified sediments show sharply defined dolomite crystals suggesting an origin as primary dolomite spherules followed by aggregation and diagenetic alteration to well crystallized dolomites.  相似文献   

Deciphering the depositional environment of the laminated Crato fossil beds (Early Cretaceous,Araripe Basin,North‐eastern Brazil)     

ULRICH HEIMHOFER  DANIEL ARIZTEGUI  MARC LENNIGER  STEPHEN P. HESSELBO  DAVID M. MARTILL  ARISTOTELES M. RIOS‐NETTO 《Sedimentology》2010,57(2):677-694

The laminated limestones of the Early Cretaceous Crato Formation of the Araripe Basin (North‐eastern Brazil) are world‐famous for their exceptionally well‐preserved and taxonomically diverse fossil fauna and flora. Whereas the fossil biota has received considerable attention, only a few studies have focused on the sedimentary characteristics and palaeoenvironmental conditions which prevailed during formation of the Crato Fossil Lagerstätte. The Nova Olinda Member represents the lowermost and thickest unit (up to 10 m) of the Crato Formation and is characterized by a pronounced rhythmically bedded, pale to dark lamination. To obtain information on palaeoenvironmental conditions, sample slabs derived from three local stratigraphic sections within the Araripe Basin were studied using high‐resolution multiproxy techniques including detailed logging, petrography, μ‐XRF scanning and stable isotope geochemistry. Integration of lithological and petrographic evidence indicates that the bulk of the Nova Olinda limestone formed via authigenic precipitation of calcite from within the upper water column, most probably induced and/or mediated by phytoplankton and picoplankton activity. A significant contribution from a benthonic, carbonate‐secreting microbial mat community is not supported by these results. Deposition took place under anoxic and, at least during certain episodes, hypersaline bottom water conditions, as evidenced by the virtually undisturbed lamination pattern, the absence of a benthonic fauna and by the occurrence of halite pseudomorphs. Input of allochthonous, catchment‐derived siliciclastics to the basin during times of laminite formation was strongly reduced. The δ¹⁸O values of authigenic carbonate precipitates (between ?7·1 and ?5·1‰) point to a ¹⁸O‐poor meteoric water source and support a continental freshwater setting for the Nova Olinda Member. The δ¹³C values, which are comparatively rich in ¹³C (between ?0·1 and +1·9‰), are interpreted to reflect reduced throughflow of water in a restricted basin, promoting equilibration with atmospheric CO₂, probably in concert with stagnant conditions and low input of soil‐derived carbon. Integration of lithological and isotopic evidence indicates a shift from closed to semi‐closed conditions towards a more open lake system during the onset of laminite deposition in the Crato Formation.  相似文献   

The Triassic ammonite Aristoptychites kolymensis (Kiparisova) from Botneheia, Spitsbergen     

MEIKE KOHLER-LOPEZ  ULRICH LEHMANN 《Polar research》1984,2(1):61-75

Aristoptychites kolymensis (Kiparisova) is investigated and described in detail from collections made at Botneheia, Spitsbergen, where it occurs at the top of the Botneheia Formation (Daonella Shale). It is a rather small species and the stratigraphically highest representative of the genus in Spitsbergen. Its suture line is remarkable by its possession of the additional U.-lobes between the internal lobe and the first umbilical lobe. A lobe of this kind has so far been described only once, with Arcestes (Proarcestes) bicarinatus by Schindewolf (1968), which suggests affinities between Ptychitidae and Arcestidae.  相似文献