Restricted Lagoonal Environment Research Articles

Microfacies and palaeoenvironments of late Cisuralian and Guadalupian (Early to Middle Permian) alatoconchid-bearing limestone in Loei fold belt, Indochina Terrane

This study presents the first record of Early Permian alatoconchid bivalves from Thailand, the Erawan section, in the north of Loei fold belt with prolific fusulines in association with gastropods, and brachiopods. Fusuline taxa are dominated by Pseudofusulina sp. with Darvasites sp., Staffella cf. labanalensis, Staffella sp., Nankinella sp., Neofusulinella sp., Schubertella sp., Pamirina darvasica, Pseudoendothyra sp. and others, indicating an Artinskian age. Fusuline wackestone with common, well-preserved smaller foraminifers, Pseudovermiporella sp. and ostracods indicates a restricted lagoon environment with low to moderate water circulation. These fossils, along with well-preserved, articulated alatoconchids in life-position, suggest the autochthonous nature of the deposits in an intertidal environment.In the central part of the fold belt, the Pak Chong section exhibits intervals of alatoconchid biostromes and coquinites. Carbonate build-ups of the alatoconchid biostromes with gregarious bivalves, in life-position embedded in a micritic wackestone matrix, suggest their preferred life habit and environment. The bivalve coquinites containing packed bivalve shells and fragments, however, indicate a high-energy event. This rock fabric along with common fusuline storm sheets suggests occasional storm events in a restricted, with moderate water circulation to open lagoon environment. Fusulines are predominated by staffellids and others including Staffella sphaerica, Staffella sp., Sphaerulina croatica, Pisolina subsphaerica, Nankinella sp., Neoschwagerina simplex, Presumatrina sp., Afghanella sp. and others, indicating a Wordian (Middle Permian) age.In the southern portion of the fold belt along the Thai-Cambodian border, the Khao Taa Ngog section contains limestone with alatoconchid shells with massive rugose corals which formed local carbonate build-ups in high-energy open platform environments. Poorly-sorted bioclasts with common fusuline tests, shell fragments and coated grains suggest an open marine, lagoon, back reef environment. The occurrence of a fusuline assemblage including Neoschwagerina sp., Yabeina sp., Lepidolina sp., Codonofusiella sp., Verbeekina verbeeki and Chusenella sp. indicates the Capitanian (late Middle Permian) age.

Nova ocorrência de Crinoidea no Pensilvaniano da Formação Itaituba, Pedreira Caltarém, norte da Bacia do Amazonas

Crinoidea from the Pennsylvanian deposits of the Itaituba Formation, Northern Amazonas Basin. The Itaituba Formation comprises part of the marine section of the Tapajós Group in the Amazonas Basin. This unit mainly comprises Pennsylvanian carbonate deposits associated with various marine invertebrate fossils. In this work, we present new records of crinoids in the Itaituba Formation in the Caltarém quarry, north platform of the Amazonas Basin. There are described and taxonomically identified, two genera of crinoids, through the study of columnals and pluricolumnals, in addition to the interpretation of the depositional environment through the analysis of carbonate microfacies. The identified specimens correspond to the species Cyclocaudex aff. typicus Moore & Jeffords, and to the genus Pentaridica Moore & Jeffords (first record in the Itaituba Formation). The textural, compositional, and paleontological analysis suggests four standard microfacies MPF 09, 10, 16, 23) and two faciological zones (ZF 7 E 8). The bioturbated bioclastic wackestones (MFP 09) and bioclastic wackestones/packstones (MFP 10) microfacies, with fossils of brachiopods, crinoids, echinoids, miliolid and fusulinid foraminifera, trilobites, and bryozoans, characterize an interior shelf environment, with a connection to an open marine circulation (ZF 7). The peloidal wackestones (MFP 16) and mudstones (MFP 23) microfacies, with a fossiliferous assemblage limited to brachiopods, echinoids and miliolid foraminifera, characterize a restricted lagoon environment (ZF 8). Paleontological data and microfacies analysis indicate the development of a lagoon environment with a diverse paleofauna of marine invertebrates in the carbonate platform of the northern bord of the Amazonas Basin, in the Monte Alegre County, during the Pennsylvanian. Keywords: taxonomy, echinoderms, microfacies, paleoenvironment, Pennsylvanian.

Impact of the late Cenomanian sea-level rise on the south Tethyan coastal ecosystem in the Middle East (Jordan, Egypt, and Tunisia): A quantitative eco-biostratigraphy approach

Sea-level rise can cause changes in coastal ecosystems. To understand the link between sea-level rise and the coastal ecosystems during the late Cenomanian of the southern Tethys, five exposed sections from three Middle East countries were quantitatively analyzed. The Unitary Association (UA) method allowed a two-fold increase in the resolution of zones compared to the Oppel method. Five UAs were obtained from analyses of both ammonite and benthic fauna. However, they were grouped into 3 UA Zones (UAZ) to enable basin-wide correlation. These zones were linked to one and half 3rd-order depositional cycles. During the Neolobites vibrayeanus/ Calycoceras guerangeri ammonite zone (95.5–94.4 Ma), high-energy shallow subtidal environments were formed by the transgression that followed the global sequence boundary ‘KCe 4’. They were dominated by stationary epifauna and suspension-feeders (mainly oyster bivalves). During highstand, a restricted lagoonal environment prevailed, where oyster bivalves, which have well-known adaptive strategies, were still dominant. No ammonites were recorded in this zone. Upward, the fauna has underwent a major shift, which documents the beginning of a new depositional sequence above a regional sequence boundary ‘KCe 5’ with a gradual increase of hemipelagic organic-rich sediments and planktic/nektic fauna in addition to infaunal deposit-feeders and mobile benthos, which have lived in a deeper subtidal environment (Vascoceras cauvini/Pseudospidoceras pseudonodosides ammonite zone; 94.4–93.8 Ma). This dramatic change in the character of the macrofauna at the Cenomanian/Turonian boundary (maximum flooding of KCe 5) can be attributed to the hydrodynamic changes associated with the eustatic sea-level rise. Therefore, the sea-level-based faunal changes can be integrated in sequence stratigraphic analyses. The geographic reproducibility of the UA mirrors the delay of the transgressive onlap in proximal sections, and thus, can be used to define transgressive and maximum flooding surfaces. This eco-biostratigraphic scheme can be implemented in reliable large-scale correlations.

New Dinosaur Tracks from the Lower Barremian of Portugal (Areia do Mastro Formation, Cape Espichel)

We present a new tracksite with multiple dinosaur tracks from the lowermost Barremian (Lower Cretaceous) of the Cape Espichel (Sesimbra, Portugal). The tracks are localized on three beds on the top carbonate beds of the Areia do Mastro Formation. Those bioclastic, nodular limestones were deposited in a very shallow subtidal-intertidal, restricted lagoon environment. The track surfaces are very dinoturbated, with a substantial number of tracks. Several tracks assign to sauropods, ornithopods and theropods dinosaurs were recorded. Due to heavy bioturbation and the preservation conditions, it is not possible to define trackways; some preliminary work done on the tracks could disclose some behaviours of their producers. Several species of carnivore and herbivore dinosaurs crossed that large area at different times. Herbivores may have used the lagoon margin as passage between feeding spots, while carnivores frequented the area to hunt in groups or individually.

Biotic response to the latest Cenomanian drowning and OAE2: A case study from the Eastern Desert of Egypt

The changes in macrofauna and microfauna, before, during and after the latest Cenomanian global Oceanic Anoxic Event (OAE2), from the Eastern Desert of Egypt are documented, along with an inferred paleoenvironment. The age of the studied OAE2 interval is constrained by the last occurrence of the marker calcareous nannofossils species Axopodorhabdus albianus along with the previously identified positive δ13C excursion from the coeval ammonite Vascoceras cauvini Zone (= Neocardioceras juddii Zone), enabling correlation with the peak ‘b’ of the OAE2. Based on the studied microfaunal assemblages, a warm shallow restricted lagoonal environment with mesotrophic conditions and strong seasonality is inferred. The presence of a rare ammonite (and ostracods) attest to the intermittent introduction of marine waters within this inner ramp setting. In terms of sequence stratigraphy, two 3rd order depositional sequences are recorded. The top surface of the first depositional sequence, at the sequence boundary, SB Ce 5 (the start of the OAE2), is marked by an abrupt faunal change with reduced abundances of the macrofaunal elements. This is in tune with other Egyptian records of relatively smaller loss (10 %) at the Cenomanian-Turonian boundary, as compared to much higher numbers (53–79% of species), globally. This faunal (biotic bottleneck) and lithological change (from siliciclastic-dominated deposits to a largely carbonate-dominated one) at the SB Ce 5 is attributed as a response to the latest Cenomanian drowning (the highest sea-level during the Phanerozoic), that also resulted in the formation of carbonate platform.

OXYGEN ISOTOPE PROFILES OF UPPERMOST JURASSIC VERTEBRATE TEETH AND OYSTER SHELLS: A RECORD OF PALEOENVIRONMENTAL CHANGES AND ANIMAL HABITATS

ABSTRACTHigh resolution oxygen isotopes profiles of well-preserved uppermost Jurassic oyster shells and vertebrate (ichthyosaur and fish) teeth from Central Poland were obtained using a microdrill and an ion microprobe (SHRIMP IIe/MC). Internal variability of δ18O values of oyster shells (-1.7 to 1.3‰ VPDB) collected from the offshore interval of the studied section is greater than that determined previously from bulk oysters. Relatively high δ18O values of the studied oysters may be linked to a slight increase in the salinity of the mid-Polish basin. Low δ18O values of co-occurring ichthyosaur tooth enamel substantiate endothermy of these reptiles. An observed ontogenetic increase in the ichthyosaur enamel δ18O values (from ∼ 19.4 to ∼ 21.6‰ VSMOW) may be a result of long distance migrations although the effect of metabolic factors at rising body mass cannot be completely excluded. It is postulated that δ18O values of the latest portion of the ichthyosaur tooth enamel can be used for the calculation of ancient water oxygen isotope composition and verification of oxygen isotope temperatures. High δ18O values of the enameloid of Caturus lungfishes (23.6 to 26.5‰ VSMOW) collected from an upper part of the studied section, which was deposited in a restricted lagoonal environment after a marine regression, are probably a result of a high evaporation rate. The fishes could have breathed atmospheric air and withstood episodes of water hypoxia. Internal oxygen isotope records of the shells and teeth are promising proxies for studies of the paleoenvironment and activity of animals.

Sedimentological Characteristics And Paleoenvironmental Implication Of Triassic Vertebrate Localities In Villány (Villány Hills, Southern Hungary)

Abstract There are two Triassic vertebrate sites in Villány Hills (Southern Hungary), where productive and continuous excavations have been carried out in the last six years resulting in a rich and diversified assemblage of shallow marine to coastal animals. The studied formations belong to the Villány–Bihor Unit of the Tisza Megaunit, which was located at the passive margin of the European Plate during the Triassic. The relatively diverse vertebrate assemblage was collected from a Road-cut on Templom Hill and a newly discovered site at a construction zone located on the Somssich Hill. Four main lithofacies were identified and interpreted in the newly discovered Construction vertebrate site consisting of dolomite (deposited in a shallow, restricted lagoon environment), dolomarl (shallow marine sediments with enhanced terrigenous input), reddish silty claystone (paleosol) and sandstone (terrigenous provenance) indicating that the sediments of the Construction vertebrate site were formed in a subtidal to peritidal zone of the inner ramp environment, where the main controlling factor of the alternating sedimentation was the climate change. However, the recurring paleosol formation in the middle part of the section also indicates a rapid sea-level fall when the marine sediments were repeatedly exposed to subaerial conditions. In the Road-cut site the siliciclastic sediments of the Mészhegy Sandstone Formation are exposed, representing a nearshore, shallow marine environment characterized by high siliciclastic input from the mainland.

Early diagenesis of the lower Vectis Formation, Wealden Group Lower Cretaceous, Barremian), Sandown, Isle of Wight

The Vectis Formation was deposited in a restricted lagoonal environment that periodically dried up, as indicated by the presence of desiccation surfaces. The fauna indicates that salinities fluctuated significantly during deposition, from fresh to brackish-marine. Pre-burial berthierine-rich clay replaced faecal pellets in the sediment, infilling desiccation cracks, during re-flooding of the lagoon. Concretions formed by early pyrite and apatite cementation during initial burial in lake sediment, with organic debris of fish and wood, acting as nuclei and a trigger for cementation. With subsequent partial or complete exhumation oxidation of the pyrite occurred, prior to cementation by Mn siderite. All further concretion cementation occurred within the oxic to sub-oxic diagenetic zones. Textural relationships indicate that commonly occurring baryte formedafter pyrite oxidation and represents the last diagenetic mineral phase.

Ichnology and depositional environments of the Upper Ordovician Stony Mountain Formation in the Williston Basin, Canada: Refining ichnofacies and ichnofabric models for Epeiric Sea carbonates

Ordovician epeiric sea carbonates in intracratonic basins of Laurentia are enigmatic due to their unique depositional settings and the absence of modern analogs. Integrated ichnologic and sedimentologic analysis of the Upper Ordovician Stony Mountain Formation in the Williston Basin of Canada allows recognition of neritic-marine, nearshore-marine, open-lagoon, restricted-lagoon, peritidal sand-shoal and peritidal-flat subenvironments. The Cruziana ichnofacies occurs in neritic (between fair-weather and storm wave bases) and nearshore (around fair-weather wave base) marine environments. The depauperate Cruziana ichnofacies is present in open- and restricted-lagoon environments, indicating a shift from fully marine to stressed conditions. In the open lagoon, composite ichnofabrics related to omission surfaces illustrate the low rates of background sedimentation interrupted by event deposition and early cementation, illustrating the Glossifungites and Trypanites ichnofacies. The decreased size of discrete burrows in the restricted lagoon is attributed to reduced oxygenation under stagnation rather than hypersalinity. The peritidal complex includes high-energy sand shoals and low-energy tidal flats. Only monospecific colonization took place sporadically in associated subtidal environments within the peritidal complex deposits.

Stratigraphic correlation and paleoenvironmental analysis of the hydrocarbon-bearing Early Miocene Euphrates and Jeribe formations in the Zagros folded-thrust belt

The Lower Miocene Euphrates and Jeribe formations are considered as the main targets of the Tertiary petroleum system in the western part of the Zagros Basin. The formations consist of carbonates with some evaporate intercalations of the Dhiban Formation. This study utilized data from a field investigation including newly described outcrop sections and newly discovered productive oil fields within the Kirkuk embayment zone of the Zagros fold and thrust belt such as Sarqala and Kurdamir wells. This work is the first to show a stratigraphic correlation and paleoenvironmental interpretation by investigating both well data and new outcrop data. Three depositional environments were identified, (1) an inner and outer ramp belts environment, (2) shoal environment, and (3) restricted lagoon environment. Within these 3 environments, 12 microfacies were identified, based on the distribution of fauna mainly benthonic foraminifera, rock textures, and sedimentary structures. The inferred shallow water depths and variable salinities in both the Euphrates Formation and Jeribe Formation carbonates are consistent with deposition on the inner ramp (restricted lagoon and shoal) environments. Those found in the Euphrates Formation constrained the depositional environment to the restricted lagoon and shoal environment, while the microfacies in the Jeribe Formation provided evidence for an inner ramp and middle to outer ramp belt environments. This study represents the first detailed research that focuses on the stratigraphic correlation and changes in carbonate facies with the main aim to provide a wider understanding of stratigraphy of these carbonate reservoirs throughout the northern part of Iraq.

Diverse and durophagous: Early Carboniferous chondrichthyans from the Scottish Borders

ABSTRACTChondrichthyan teeth from a new locality in the Scottish Borders supply additional evidence of Early Carboniferous chondrichthyans in the UK. The interbedded dolostones and siltstones of the Ballagan Formation exposed along Whitrope Burn are interpreted as representing a restricted lagoonal environment that received significant amounts of land-derived sediment. This site is palynologically dated to the latest Tournaisian–early Viséan. The diverse dental fauna documented here is dominated by large crushing holocephalan toothplates, with very few, small non-crushing chondrichthyan teeth. Two new taxa are named and described. Our samples are consistent with worldwide evidence that chondrichthyan crushing faunas are common following the Hangenberg extinction event. The lagoonal habitat represented by Whitrope Burn may represent a temporary refugium that was host to a near-relict fauna dominated by large holocephalan chondrichthyans with crushing dentitions. Many of these had already become scarce in other localities by the Viséan and become extinct later in the Carboniferous. This fauna provides evidence of early endemism or niche separation within European chondrichthyan faunas at this time. This evidence points to a complex picture in which the diversity of durophagous chondrichthyans is controlled by narrow spatial shifts in niche availability over time.

Multiphase dolomitization of deeply buried Cambrian petroleum reservoirs, Tarim Basin, north‐west China

AbstractCambrian dolostone reservoirs in the Tarim Basin, China, have significant potential for future discoveries of petroleum, although exploration and production planning is hampered by limited understanding of the occurrence and distribution of dolomite in such ancient rocks buried to nearly 8 km. The study herein accessed new drill core samples which provide an opportunity to understand the dolomitization process in deep basins and its impact on Cambrian carbonate reservoirs. This study documents the origin of the dolostone reservoirs using a combination of petrology, fluid‐inclusion microthermometry, and stable and radiogenic‐isotopes of outcrop and core samples. An initial microbial dolomitization event occurred in restricted lagoon environments and is characterized by depleted δ13C values. Dolomicrite from lagoonal and sabkha facies, some fabric‐retentive dolomite and fabric‐obliterative dolomite in the peloidal shoal and reef facies show the highest δ18O values. These dolomites represent relatively early reflux dolomitization. The local occurrence of K‐feldspar in dolomicrite indicates that some radiogenic strontium was contributed via terrigenous input. Most fabric‐retentive dolomite may have precipitated from seawater at slightly elevated temperatures, suggested by petrological and isotopic data. Most fabric‐obliterative dolomite, and medium to coarse dolomite cement, formed between 90°C and 130°C from marine evaporitic brine. Saddle dolomite formed by hydrothermal dolomitization at temperatures up to 170°C, and involved the mixing of connate brines with Sr‐ enriched hydrothermal fluids. Intercrystalline, moldic, and breccia porosities are due to the early stages of dolomitization. Macroscopic, intergranular, vuggy, fracture and dissolution porosity are due to burial‐related dissolution and regional hydrothermal events. This work has shown that old (for example, Cambrian or even Precambrian) sucrosic dolomite with associated anhydrite, buried to as much as 8000 m, can still have a high potential for hosting substantial hydrocarbon resources and should be globally targeted for future exploration.

Paleogene carbonate microfacies and sandstone provenance (Gamba area, South Tibet): Stratigraphic response to initial India–Asia continental collision

The Paleogene marine strata in the Gamba area of south Tibet comprise carbonates of the Zongpu Formation and siliciclastic rocks of the Enba and Zhaguo Formations, documenting the final stages of marine deposition in the Tethyan Himalaya. The ∼350-m-thick Zongpu Formation was dated as late Danian to Ypresian based on larger benthic foraminifers. Thirteen distinct microfacies identify three sedimentary environments. Mudstone, wackestone with Udoteacean algae, bioclastic-peloidal packstone, packstone with Rotaliids and green algae, floatstone with Alveolina and Orbitolites were deposited in restricted lagoonal environments. Bioclastic packstone and grainstone with Rotaliids were deposited in high-energy shoal environments. Floatstones with Nummulitids or Alveolinids were deposited in shallow open-marine environments. The Zongpu Formation was accumulated on a carbonate ramp. It documents two deepening-upward sequences separated by an unconformity corresponding to the Palaeocene/Eocene boundary and marked by a conglomerate with limestone clasts. The overlying Enba Formation comprises greenish grey calcareous shales intercalated with litho-quartzose sandstones in the upper part and capped by subaerial litho-quartzose red beds of the Zhaguo Formation. Petrographic analysis, detrital zircon geochronology and Hf isotopic data indicate that detritus in the Enba and Zhaguo Formations, deposited on the Indian passive margin, was derived from the Asian active margin in the north. These clastic units were thus deposited after the onset of the India–Asia continental collision in the early Himalayan foreland basin. Major lithological and paleoenvironmental changes occurred at three stratigraphic levels: the Jidula/Zongpu boundary (∼62Ma), the Paleocene/Eocene boundary (∼56Ma) and the Zongpu/Enba boundary (∼51Ma). Our provenance study confirms that the India–Asia collision was already under way during the deposition of the Enba Member (i.e., by ∼51Ma) and, along with facies analysis and general palaeogeographic considerations, indicates that Neo-Tethys was still wide open during the Early–Middle Paleocene. It is thus argued, consistently with previous studies, that the Paleocene/Eocene disconformity documented in the Gamba area as in the northwestern Tethyan Himalaya is likely to record flexural uplift consequent to initial underthrusting of the Indian continental margin beneath Asia at, or just a little earlier than, 56Ma.

Early diagenesis in meteoric versus brackish environments: Example of the Late Oligocene-Early Miocene, littoral, mixed sedimentary succession of Carry-Le-Rouet (southeastern France)

AbstractIn the Carry-Le-Rouet region (southeastern France), the well exposed Late Oligocene-Early Miocene succession allows studying the early diagenesis in meteoric and brackish environments. This area provides unique and continuous outcrops of a mixed sedimentary succession (carbonate-siliciclastic shallow facies) with five particular sedimentary discontinuities resulting from various processes such as subaerial exposure, submarine erosion or bioturbation.Results from the diagenetic characterization (petrography and isotope geochemistry) show that the succession may be divided into three parts. The base of the series is dominated by diagenetic processes associated with brackish water, reflecting a restricted lagoonal environment. Dissolution and mineral replacement occurred directly under the sediment-water interface and a subsequent reprecipitation of the dissolved calcium carbonate took place below this layer. The precipitated calcite is non-ferroan and dull luminescent, showing highly variable stable C- & O-isotopic signatures (−6.31‰ to −0.08‰ for δ13CV-PDB and −5,78‰ to −1,36‰ for δ18OV-PDB), organized in a covariant trend, typical of mixed fluids. The middle part of the series, show a progressive evolution to open marine conditions and records two potential emersion events, associated with the development of meteoric vadose and phreatic conditions. The postulated vadose zones are dominated by mineral replacement rather than leaching and characterized by two cements: a non-ferroan and non-luminescent calcite, changing downward to zoned cement. Isotopic signatures of these calcites are ranging from −6.45‰ to −5.10‰ for δ13CV-PDB and −5,44‰ to −4,17‰ for δ18OV-PDB. Below this zone, a ferroan, non-luminescent calcite (−3.25‰ to −1.18‰ for δ13CV-PDB and −4,93‰ to −3,52‰ for δ18OV-PDB) is observed, suggesting precipitation under reducing conditions associated to a confined phreatic zone, isolated from the overlying zones and the recharge area by a marly interval. The third part of the series (at the top), partly eroded, may have undergone at least one emersion event, with the initial development of a dull cement followed by a non-ferroan, non-luminescent cement. This is linked to a gradual change from downdip slightly reducing to updip oxidizing conditions.The early timing of the diagenetic modifications, the differences of diagenetic patterns observed in each interval and the absence of common trends in the series tend to indicate multiple episodes of early diagenesis, associated to sedimentary discontinuities (more specifically exposure surfaces). These discontinuities act as major controls on the repartition of the diagenetic phases. The excellent preservation of the early diagenetic transformations is linked to the shallow total burial depth, and the lack of mesogenetic and telogenetic imprint. This study also highlighted the influence of the Nerthe massif that acted as a principal meteoric fluid recharge area located less than 1 km away from the sedimentary system.

Effects of stocking density on survival, growth and biochemical composition of cultured mussels (Mytilus galloprovincialis, Lamarck 1819) from an offshore submerged longline system

AbstractThis study examined an offshore submerged mus-sel longline system, in the Black Sea, from May2009 to May 2010. The system was allowed1 year for spat collection. After a 1-year spat col-lection period, some spat collectors were leftuntouched (NS), and some spat collectors weregrazed and socked (S) for a grow-out study in May2009. The effects of stocking density on thegrowth and survival of the S and NS mussels wereexamined. The biochemical composition of the mus-sels was also determined. Environmental factorsincluding temperature, salinity, chlorophyll a, totalsuspended matter, inorganic matter and organicmatter were monitored monthly during the experi-mental period. In May 2010, the mean length andlive weight of the S and NS mussels were60.46 0.60 mm and 53.34 0.37 mm, respec-tively, and 20.50 0.50 g and 13.11 0.26 grespectively. Mean moisture and ash were 82.35 0.47% and 6.67 0.44% respectively. Mean car-bohydrate, protein and lipid were 27.74 2.40%,57.68 2.15% and 7.91 0.68% respectively.These results indicate that a submerged offshoremussel culture system in the Black Sea can becommercially convenient. In addition, stock man-agement via thinning out of the spat can consider-ably increase the marketable size of mussels,reduce harvest time and produce better growth.Keywords: Mussel, offshore, density, growth,survival, biochemicalIntroductionUnited Nations Food and Agricultural Organiza-tion (FAO) statistics indicates that mussels are oneof the most popular cultured species. The culturingof mussels has increased from 1307 thousandtonnes to 1812 thousand tonnes in the last fewdecades (FAO/Fishstat Plus 2012).For a long time, mussel farms have been limitedto sheltered coastal lagoons (Burbridge, Hendrick,Roth & Rosenthal 2001). According to Danioux,Loste and Paquotte (1997), coastal lagoons haverich and easily accessible but fragile environmentsthat have been exploited to their maximum spatialand biological capacity. These researchers havealso stated that several risk factors, at times simul-taneously, have limited the expansion of themussel farming activity in the restricted lagoonenvironment: (i) the necessary intensification ofproduction to reduce production costs; (ii) pollu-tion from industrial and domestic sources, whichproduces high mortality at times and (iii) thelimited renewal of the environment due to a lackof strong tides, which brings with it a dystrophiccrisis and anoxia risk. Inshore sites have alsoproven to have lower growth and higher diseaserates, with greater risks of contamination fromoveruse and other activities. Due to these chal-lenges, to date, the mussel production achievedhas not increased enough to meet demand. As aresult, offshore mussel culture has been suggestedas a solution to meet the growing demand(Langan 2008).

Evolution of the sebkha Dreîaa (South-Eastern Tunisia, Gulf of Gabes) during the Late Holocene: Response of ostracod assemblages

The quantitative and qualitative study of the ostracod assemblages supported by the correspondence analysis (CA) allowed the reconstruction of the palaeoenvironnemental change during the Holocene in the sebkha Dreîaa of Skhira (Gulf of Gabes, SE Tunisia). Five phases were distinguished: the first phase (>cal. 6471–6874 yr BP) coincides with the first Holocene marine transgression following the deposition of the continental Holocene series. It induces the setting of an open lagoon where numerous Bivalvia, Gastropoda and marine ostracods lived. The second one (cal. 6471–6874 yr BP) is characterized by the development of brackish ostracods, high diversity index values and comparable percentages of the brackish, lagoonal and coastal assemblages. It corresponds to an open lagoon subjected to estuarine influences. During the third phase (cal. 3350–3752 yr BP), a marine environment, marked by the enrichment of marine ostracods, is evolving toward the closing. The settlement of the restricted lagoonal environments is linked to the building-up of sandy spit. At cal. 2839–3057 yr BP, the dominance of coastal ostracods, associated with coarse sands, show an open lagoon and probably a marine transgression evidenced by the progressive modification in the ostracods assemblages. After this transgression, the southern part of Sebkha of Dreîaa emerged and evolved towards the present state. The last phase, cal. 515–777 yr BP, is marked by a strong marine influence, in the northern part of the sebkha, with transport of marine Bivalvia, Gastropoda and ostracods towards the inner lagoon by means of storms. The rupture of sandy spits induced the introduction of marine macrofauna and microfauna which were accumulated and associated with charcoals and coarse sands.

Ichnology and sedimentology of the Triassic carbonates of North‐west Sardinia, Italy

AbstractThe classical Middle to Upper Triassic carbonate sections at Monte Santa Giusta and Punta del Lavatoio, North‐west Sardinia (Italy), referred to the Muschelkalk and Keuper lithofacies group, are revisited and their trace fossil content is investigated for the first time. A combined ichnological and sedimentological study reveals insights into the depositional environments, regional context, palaeogeography and sequence stratigraphy. The results indicate deposition on a homoclinal carbonate ramp with broad facies belts. All recognized trace fossils are also known from time‐equivalent deposits of Germany and thus indicate a close affinity between the North‐west Sardinian Triassic and the Germanic Basin. Only a few trace fossils are particularly abundant and these indicate opportunistic colonization by their producers, which is probably related to restricted endobenthic conditions due to reduced oxygen and/or increased salinity. The trace fossil association can be grouped into a softground suite belonging to the Cruziana ichnofacies, and a firmground suite of the Glossifungites ichnofacies. This discrimination enables an interpretation of the northern Monte Santa Giusta section as a carbonate ramp with extensive tidal flats and abundant carbonate accumulation in a relatively proximal position, whereas the southern Punta del Lavatoio section exhibits broad lagoonal environments with reduced sedimentation in a deeper and more Tethys‐influenced area. The Sardinian sections are ichnologically similar to the Anisian–Ladinian succession known from the Tatra Mountains, but differ from it by having a slightly higher ichnodiversity, which again can be attributed to a less restricted lagoonal environment. This study demonstrates the importance of integrating trace fossil analysis in sedimentological and palaeontological investigations of carbonate systems.

Organic carbon isotope values from the Late Permian Seis/Siusi succession (Dolomites, Italy): Implications for palaeoenvironmental changes

<strong class="journal-contentHeaderColor">Abstract.</strong> The Permian-Triassic boundary is marked by a globally prominent negative carbon isotope excursion traceable in marine carbonates and organic matter. In the shallow marine carbonate succession at Seis/Siusi (Dolomites, Italy), the &delta;¹³C_carb and &delta;¹³C_org signatures follow the general Permian-Triassic boundary carbon isotope trend, but the &delta;¹³C_org values are slightly less depleted in ¹³C in two episodes representing restricted lagoonal environments and in the period around the Tesero Oolite Horizon. This isotopically less depleted organic matter in the lagoons is interpreted to be most likely caused by poor oxygen ventilation and/or slightly modified salinity which may have led to restricted bioproductivity and increased hence the relative amounts of continental-sourced organic matter. In addition, elevated riverine influx and supply of terrestrial organic matter, perhaps triggered by a wet period, might be the cause for the relatively less depleted ¹³C in the organic matter around the Tesero Oolite Horizon and in overlying sediments. <br><br> doi:<a href="http://dx.doi.org/10.1002/mmng.201100008" target="_blank">10.1002/mmng.201100008</a>

Organic carbon isotope values from the Late Permian Seis/Siusi succession (Dolomites, Italy): Implications for palaeoenvironmental changes

The Permian-Triassic boundary is marked by a globally prominent negative carbon isotope excursion traceable in marine carbonates and organic matter. In the shallow marine carbonate succession at Seis/Siusi (Dolomites, Italy), the &amp;delta;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;carb&lt;/sub&gt; and &amp;delta;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;org&lt;/sub&gt; signatures follow the general Permian-Triassic boundary carbon isotope trend, but the &amp;delta;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;org&lt;/sub&gt; values are slightly less depleted in &lt;sup&gt;13&lt;/sup&gt;C in two episodes representing restricted lagoonal environments and in the period around the Tesero Oolite Horizon. This isotopically less depleted organic matter in the lagoons is interpreted to be most likely caused by poor oxygen ventilation and/or slightly modified salinity which may have led to restricted bioproductivity and increased hence the relative amounts of continental-sourced organic matter. In addition, elevated riverine influx and supply of terrestrial organic matter, perhaps triggered by a wet period, might be the cause for the relatively less depleted &lt;sup&gt;13&lt;/sup&gt;C in the organic matter around the Tesero Oolite Horizon and in overlying sediments. &lt;br&gt;&lt;br&gt; doi:&lt;a href="http://dx.doi.org/10.1002/mmng.201100008" target="_blank"&gt;10.1002/mmng.201100008&lt;/a&gt;

Using an Artificial-Neural-Network Method To Predict Carbonate Well Log Facies Successfully

Summary The Maastrichtian (Upper Cretaceous) reservoir is one of five prolific oil reservoirs in the giant Wafra oil field. The Maastrichtian oil production is largely from subtidal dolomites at an average depth of 2,500 ft. Carbonate deposition occurred on a very gently dipping, shallow, arid, and restricted ramp setting that transitioned between normal marine conditions to restricted lagoonal environments. The average porosity of the reservoir interval is approximately 15%, although productive zones have porosity values up to 30–40%. The average permeability of the reservoir interval is approximately 30 md. Individual core plugs have measured permeability up to 1,200 md. Efforts to predict sedimentary facies from well logs in carbonate reservoirs is difficult because of the complex carbonate sedimentary facies structures, strong diagenetic overprint, and challenging log analysis in part owing to the presence of vugs and fractures. In the study, a workflow including (1) core description preprocessing, (2) log- and core-data cleanup, and (3) probabilistic-neural-network (PNN) facies analysis was used to predict facies from log data accurately. After evaluation of a variety of statistical approaches, a PNN-based approach was used to predict facies from well-log data. The PNN was selected as a tool because it has the capability to delineate complex nonlinear relationships between facies and log data. The PNN method was shown to outperform multivariate statistical algorithms and, in this study, gave good prediction accuracy (above 70%). The prediction uncertainty was quantified by two probabilistic logs—discriminant ability and overall confidence. These probabilistic logs can be used to evaluate the prediction uncertainty during interpretation. Lithofacies were predicted for 15 key wells in the Wafra Maastrichtian reservoir and were effectively used to extend the understanding of the Maastrichtian stratigraphy, depositional setting, and facies distribution.