Deep-water stromatolites andFrutexites Maslov from the early and Middle Jurassic of S-Germany and Austria

Despite extensive discussions during the last 20 years stromatolites are still used by many geologists as unequivocal indicators of very shallow-water conditions. We investigated four stratigraphic units from the Lower and Middle Jurassic of southern Germany (Posidonien-Schiefer, Amaltheen-Ton) and of the Northern Calcareous Alps (Adneter Kalk, Klauskalk), which were formerly interpreted as shallow marine sediments by some authors due to the occurrence of stromatolites. Our interpretations of the macro-, micro- and ultrafacies of these sediments are not compatible with shallow-water settings. We therefore propose a deep-marine, aphotic origin of these stromatolites. Former interpretations o…

Controls of mud mound formation: The Early Devonian Kess-Kess carbonates of the Hamar Laghdad, Antiatlas, Morocco

The origin and development of Early Devonian (late Pragian to late Zlichovian; predominantly uppermost Zlichovian as indicated by conodont faunas) mud mounds of the Hamar Laghdad area in the eastern Antiatlas, Morocco, are controlled by extrinsic and intrinsic factors. Extrinsic factors include the existence of a paleohigh (Lochkovian volcaniclastics), unidirectional currents and repeated storm events as well as sea level fluctuations. Intrinsic, biologically induced factors are the preferred growth of organisms on the top and the flanks of the mounds because of more favourable ecological conditions, and a rapid synsedimentary lithification of the steep mound flanks by interskeletal cementa…

Porites corals from Crete (Greece) open a window into Late Miocene (10Ma) seasonal and interannual climate variability

Variations in the biotic composition of marine shallow water carbonates document global climatic changes. However, a discontinuous stratigraphic record and uncertainties regarding the ages limit the significance of shallow water carbonates as palaeoclimatic archives on geological time-scales. Notwithstanding these deficits, the environmental information stored in the skeleton of reef biota is a unique source of information that resolves seasonal to interannual climate variability in geological time. Application of the method to corals from carbonate rocks is usually restricted to the past 130,000yr, because the aragonite skeleton undergoes rapid diagenetic alteration. Consequently, reconstr…

Controls on modern carbonate sedimentation on warm-temperate to arctic coasts, shelves and seamounts in the Northern Hemisphere: Implications for fossil counterparts

In contrast to the well studied tropical carbonate environments, interest in non-tropical carbonate deposition was rather low until the basic ideas of theForamol-concept were outlined byLees & Buller (1972). In the following two decades studies on non-tropical carbonate settings evolved as a new and exciting branch of carbonate sedimentology (seeNelson 1988). This is archieved in a great number of publications dealing on temperate carbonate deposits from numerous coastal and open shelf settings on both hemispheres. The existence of wide extended carbonate depositional systems and even reefal frameworks in Subarctic and Arctic seas which are in focus by our research group made it possible to…

Lowstand carbonates, highstand sandstones?

The sedimentary facies, sediment dynamics and sequence architecture of modern high-energy shelves in the mid and high latitudes are largely governed by wave abrasion processes. Cool-water carbonates may form there, if the influx and/or net accretion of siliciclastics is kept at a minimum. Little dilution of the carbonate produced in situ is generally promoted by a wide "epicontinental" shelf, subdued topography of the adjacent mainland, the predominance of limestone outcrops, and an arid climate. The aforementioned requirements are rarely met, and thus will automatically lead to the formation of mixed siliciclastic-cool-water carbonates. Such an example is found in the Early to Mid-Miocene …

Chemical composition of modern and fossil hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation – Part 2: Alkaline earth elements as tracers of watershed hydrochemistry and provenance

Abstract. For reconstructing environmental change in terrestrial realms the geochemistry of fossil bioapatite in bones and teeth is among the most promising applications. This study demonstrates that alkaline earth elements in enamel of Hippopotamids, in particular Ba and Sr are tracers for water provenance and hydrochemistry. The studied specimens are molar teeth from Hippopotamids found in modern and fossil lacustrine settings of the Western Branch of the East African Rift system (Lake Kikorongo, Lake Albert, and Lake Malawi) and from modern fluvial environments of the Nile River. Concentrations in enamel vary by ca. two orders of magnitude for Ba (120–9336 μg g−1) as well as for Sr (9–21…

Chemical composition of modern and fossil Hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation – Part 1: Major and minor element variation

Bioapatite in mammalian teeth is readily preserved in continental sediments and represents a very important archive for reconstructions of environment and climate evolution. This project provides a comprehensive data base of major, minor and trace element and isotope tracers for tooth apatite using a variety of microanalytical techniques. The aim is to identify specific sedimentary environments and to improve our understanding on the interaction between internal metabolic processes during tooth formation and external nutritional control and secondary alteration effects. Here, we use the electron microprobe to determine the major and minor element contents of fossil and modern molar enamel, …

Shallow-marine carbonates of the tropical-temperature transition zone: effects of hinterland climate and basin physiography (late Miocene, Crete, Greece)

Tarbellastraea (Scleractinia): A new stable isotope archive for Late Miocene paleoenvironments in the Mediterranean

Abstract Geochemical proxy records of sea surface temperature (SST) or sea surface salinity (SSS) variability on intra- and interannual time-scales in corals from geological periods older than Pleistocene are extremely rare due to pervasive diagenetic alteration of coralline aragonite. Very recently, however, stable isotope data (δ18O, δ13C) from specimens of Porites of Late Miocene age (10 Ma) have been shown to preserve original environmental signatures. In this paper we describe new finds of the zooxanthellate corals Porites and Tarbellastraea in exceptional aragonite preservation from the island of Crete in sediments of Tortonian (∼ 9 Ma) and Early Messinian (∼ 7 Ma) age. Systematic, co…

Calcification response of reef corals to seasonal upwelling in the northern Arabian Sea (Masirah Island, Oman)

Tropical shallow-water reefs are the most diverse ecosystems in the ocean. Their persistence rests upon adequate calcification rates of the reef building biota, such as reef corals. Coral calcification is favoured in oligotrophic environments with high seawater saturation states of aragonite (Ωsw), which leads to an increased vulnerability to anthropogenic ocean acidification and eutrophication. Here we present Porites calcification records from the northern Arabian Sea upwelling zone and investigate the coral calcification response to low Ωsw and high nutrient concentrations due to seasonal upwelling. The calcification rate was determined from the product of skeletal extension rate and bul…

Sedimentary model and high-frequency cyclicity in a Mediterranean, shallow-shelf, temperate-carbonate environment (uppermost Miocene, Agua Amarga Basin, Southern Spain)

Uppermost Tortonian to lower Messinian temperate carbonates crop out in the Agua Amarga Basin (SE Spain). They consist of four units. The lower three units can be tentatively assigned to the lowstand systems tract of a fourth-order sequence, constituting in turn the lowstand (‘megatrough unit’), transgressive (‘breccia unit’) and highstand (‘bedded unit’) stages of a higher-order cycle. All these materials were deposited in a small pull-apart basin related to the sinistral Carboneras strike-slip fault system. The best represented is the bedded unit (up to 25 m thick), which consists of bioclastic, bryozoan/bivalve-dominated calcarenites/calcirudites with abundant fragments of echinoids, bar…

Laminar Micrite Crusts and Associated Foreslope Processes, Red Sea

ABSTRACT Forereef slopes in the Red Sea of Sudan exhibit a uniform biozonation that is independent from the topography of the slopes. Below - 120 m, ledges protrude horizontally from sleep cliffs of barrier reefs and atolls as well as from patches of in situ lithified slope sediment on inclined fringing reef slopes. Free surfaces and cavities within these ledges are partly covered by laminar micrite crusts of 7-20 mm thickness. The ledges are formed by an organic framework of living azooxanthellate corals, bryozoans, serpulids and fossil red algae. They are affected by repeated episodes of boring, infilling, and cementation which obliterate much of the original fabric. Concomitant cementati…

Late Miocene sea surface salinity variability and paleoclimate conditions in the Eastern Mediterranean inferred from coral aragonite δ18O

Abstract Coral skeletons are archives of chemical proxies which enable paleoenvironmental reconstructions to be made at subannual resolution. Stable oxygen isotope ( δ 18 O) ratios of these archives reflect sea surface temperature (SST) as well as the δ 18 O composition of ambient seawater. The δ 18 O seawater composition is not only controlled by global ice build-up, but river discharge and the hydrological balance of evaporation and precipitation, all influencing sea surface salinity (SSS), also play an important role in marginal seas. New sub-annually resolved coral δ 18 O data were measured and evaluated together with published data from reef coral communities of Late Miocene age from C…

Middle Miocene graben development in Crete and its possible relation to large-scale detachment faults in the southern Aegean

The linkage between the development of south-facing Cretan graben and large-scale detachment faulting in the southern Aegean is unknown. Widespread Serravallian deposits in the Ierapetra graben of Crete supply constraints to Middle Miocene graben development in the southern Aegean. The Ierapetra graben, and by inference the Cretan graben in general, were hitherto believed to have formed as a result of sinistral transpression during N–S shortening. We argue that the formation of the Cretan graben is due to N–S extension. The south-dipping, N–S-extending Kritsa normal fault served as the master fault controlling graben development in the Ierapetra graben. The Kritsa normal fault is either an …

Eustasy and sea water Sr composition: application to high-resolution Sr-isotope stratigraphy of Miocene shallow-water carbonates

Oceanic 87 Sr/ 86 Sr-isotope ratios are strongly influenced by rates of silicate weathering and therefore linked not only to glaciation but also to sea-level change. The present study combines analysis of sequence stratigraphy and basin architecture with Sr-isotope stratigraphy in Miocene shallow-water sediments in southern Portugal and Crete (Greece). The common method is to use smoothed global sea water Sr-isotope reference curves but here a different approach is chosen. Instead, measured Sr-isotope curves are correlated with unsmoothed reference curves by identification of similar fluctuations in the order of several 100 kyr. Transgressive intervals are characterized by increasing Sr-iso…

Sequence stratigraphy and paleo-oceanography of an open-marine mixed carbonate/siliciclastic succession (Late Jurassic, Southern Germany)

The Late Jurassic epicontinental sea of South Germany protruded far to the North forming a wide bay which was rimmed by shallow-water platforms (Swiss and French Jura). This wide shelf is characterized by extensive downslope mud accumulations including siliceous sponge buildups. The bioherms are aligned along the more pericontinental parts of this shelf, which graded to the South into the Helvetic Basin of the Tethys Ocean.

Nearshore, temperate, carbonate depositional systems (lower Tortonian, Agua Amarga Basin, southern Spain): implications for carbonate sequence stratigraphy

Abstract The bryozoan-rich lower Tortonian carbonates of the Agua Amarga Basin in southern Spain (Province of Almeria) provide an example of sediments formed in a nearshore, non-tropical depositional setting. Based on data derived from logging of sections and from field mapping, these lower Tortonian carbonates form a depositional sequence, which is subdivided into several depositional systems. A lowstand systems tract, which consists of volcaniclastic fan deltas and washover deposits, formed on the leeward side of a basement shoal which delimited the basin towards the south. A transgressive systems tract, which is characterised by a landward encroachment of deposits, is represented by subm…

Freshwater discharge and sediment dispersal — Control on growth, ecological structure and geometry of Late Miocene shallow-water coral ecosystems (early Tortonian, Crete/Greece)

Abstract Insolation-driven oceanographic changes are well documented in the Mediterranean deep-sea record and reflect episodes of high precipitation and/or freshwater discharge. In the shallow-water record, however, changes in relative sea-level and sea surface temperature are usually regarded as prime controls on Miocene coral reefs, whereas pulses of freshwater influx represent a hitherto unrecognized factor influencing their growth, ecological structure and geometry. On the island of Crete (NW Messara Basin, Greece) early Tortonian coral biostromes occur associated with deltas along the basin margin and rimming islands formed by large uplifted tectonic blocks. In turbid delta environment…

LA-ICP-MS analyses on coral growth increments reveal heavy winter rain in the Eastern Mediterranean at 9 Ma

Abstract Sediment particles incorporated into coral skeletons reflect variation in composition and amount of suspended material in ambient water during coral growth. They can be used to identify periods of enhanced storm frequency and associated freshwater discharge. Tortonian (Late Miocene) Porites corals from Crete (Aegean Sea, Eastern Mediterranean) show pronounced annual density bands in X-ray photographs. δ18O compositional variability reflects the annual banding equivalent with a ~ 7 °C annual sea surface temperature (SST) cycle over a seven-year period. Fine sediment particles are concentrated in layers with skeletal porosity parallel to growth increments. Variations in the chemical …

Nutrients attenuate the negative effect of ocean acidification on reef coral calcification in the Arabian Sea upwelling zone (Masirah Island, Oman)

Tropical shallow-water reefs are the most diverse ecosystem in the ocean. Its persistence rests upon adequate calcification rates of the reef building biota, such as reef corals. Optimum calcification rates of reef corals occur in oligotrophic environments with high seawater saturation states of aragonite (Ωsw), which leads to increased vulnerability to anthropogenic ocean acidification and eutrophication. The calcification response of reef corals to this changing environment is largely unknown, however. Here, we present annually and sub-annually resolved records of calcification rates (n = 3) of the coral Porites from the nutrient rich and low Ωsw Arabian Sea upwe…

Coral growth bands: A new and easy to use paleothermometer in paleoenvironment analysis and paleoceanography (late Miocene, Greece)

[1] Modern scleractinian corals are classical components of marine shallow warm water ecosystems. Their occurrence and diversity patterns in the geological record have been widely used to infer past climates and environmental conditions. Coral skeletal composition data reflecting the nature of the coral environment are often affected by diagenetic alteration. Ghost structures of annual growth rhythms are, however, often well preserved in the transformed skeleton. We show that these relicts represent a valuable source of information on growth conditions of fossil corals. Annual growth bands were measured in massive hemispherical Porites of late Miocene age from the island of Crete (Greece) t…