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.     

Linkages between surface and deep circulations in the southern Japan Sea during the last 27,000 years: Evidence from planktic foraminiferal assemblages and stable isotope records

We analyzed planktic foraminiferal assemblages, oxygen and carbon isotope records, and the presence or absence of laminations to reconstruct the paleoenvironments of the southern Japan Sea since the last glacial period. Data were collected from two well-dated cores. One core (water depth 999 m) included thinly laminated mud layers, the other (water depth 283 m) contained nonlaminated sediments. Tephrochronology and accelerator mass spectrometry ¹⁴C dating of 14 horizons revealed that the two cores contained continuous records of the last 27 cal kyr. A total of 13 planktic foraminiferal species belonging to six genera were identified in down-core samples. The typical indicators of the Tsushima Current water, Globigerinoides ruber, Neogloboquadrina dutertrei, Pulleniatina obliquiloculata, Globigerinoides tenellus, and Globigerinita glutinata occurred since 9.3 cal kyr BP. Neogloboquadrina incompta, which was the dominant species in the Tsushima Current region of the modern Japan Sea, first occurred at 8.2 cal kyr BP and dominated the assemblage since 7.3 cal kyr BP. These results clearly indicate that the warm Tsushima Current started to inflow into the Japan Sea at 9.3 cal kyr BP, and the modern surface conditions in the southern Japan Sea were essentially established at 7.3 cal kyr BP. Our data and comparison of the presence or absence of laminated sediments in three locations from the southern Japan Sea suggest that deep circulation during the deglacial period was weaker than that at present. In addition, deep circulation in the modern Japan Sea, which supplies oxygen-rich water to the entire basin, started probably in association with the first inflow of the Tsushima Current beginning at 9.3 cal kyr BP.     

Holocene marine intrusions in Retba and Mbawane lakes (Senegal) evidenced by ostracod faunas

The study of a sea level fluctuation based on ostracods is carried out for the first time using core sediments of Mbawane and Retba Lakes, north coast of Senegal. A total of 26 species have been identified and most of them are encountered in the Gulf of Guinea shelf and its adjacent lagoons. The Retba Lake core, which is closer to the seashore, has yielded a richer and more diversified ostracod fauna composed of four assemblages. The F1 assemblage is composed of Cyprideis nigeriensis, Neomonoceratina iddoensis, and Aglaiocypris gambiensis, which characterises a slightly open lagoon developing under a humid climate with its edges covered with mangrove swamps. Assemblage F2, composed mainly of C. nigeriensis, N. iddoensis and “marine species”, which is richer and more diversified, points to a marine little gulf bordered by mangrove swamps. The F3 monospecific assemblage composed of C. nigeriensis indicates a drying confined lagoon under an arid climate. The F4 oligospecific association at the top, composed of C. nigeriensis and Pseudoconcha omatsolai, is typical of a slightly open saline lagoon under arid climate. Core sediments from Mbawane Lake have yielded scarce and badly preserved microfaunas which are distributed into three discontinuous levels that have been correlated to those of the Retba Lake core assemblages. The F1 assemblage composed of Leptocythere culpata and Xestoleberis sp. 2 corresponds to a slightly open lagoon covered at its bottom by marine macrophytes and algae. The F2 assemblage composed of N.iddoensis, Hemicytherura sp. A, Aglaiocypris gambiensis and Ruggieria tricostata characterises a more open lagoon bordered by mangrove swamps under a humid climate. The F3 assemblage is absent in the Mbawane Lake. The F4 monospecific association composed of C. nigeriensis characterises a drying lagoon under an arid climate. The overall marine influences were stronger in the Retba Lake while continental effects were dominant in Mbawane Lake during the same period. The two marine intrusions mentioned above may correspond to those of the Dakarian (3000 years B.P.) and the Saint-Louisian eras (2000–680 years B.P.) that existed during the Upper Holocene on the Senegalese coast.     

Ostracodes et incursions marines dans l’Holocène terminal du lac Retba (Cap Vert, Sénégal)

The study of marine incursions based on ostracods is carried out for the first time in the late Holocene, with core sediments of the Lac Retba edge. Twenty-four species are identified along the core; most of them are encountered in the Gulf of Guinea shelf and its adjacent lagoons. For the first time Buntonia olokundudui Reyment and Van Valen, Hermanites foveolata Omatsola and Soudanella africana Omatsola are recorded in Senegal. Four ostracods assemblages are evidenced along the core, corresponding to different stages of the lake evolution. Cyprideis nigeriensis Omatsola, Neomonoceratina iddoensis Omatsola and Aglaiocypris gambiensis Witte dominate the first assemblage; they indicate a lagoon slightly open to the sea and bordered with mangrove swamps under relatively humid climate conditions. The second association yields the most diversified ostracod fauna with C. nigeriensis, N. iddoensis and high proportion of reworked “marine species” which evidence a marine little gulf bordered by mangrove under a humid climate. The third, monospecific association (C. nigeriensis) is typical of a closed and hypersaline lagoon under dry climate conditions. An oligospecific association with C. nigeriensis, Pseudoconcha omatsolai Witte and very scarce reworked “marine species” occurs at the top of the core and characterises an open and hypersaline lagoon under arid climate conditions. Ostracods evidence two marine incursions. The first and the stronger one is dated here for the first time between 1420 and 1250 years B.P. The more recent is the weaker and is not yet dated. Evidence of the beginning of the Retba Lake closure towards 680 years B.P. appears at the top of the core, as indicated by high reduction of ostracods abundance, predominance of reticulate Cyprideis and disappearance of the “marine species”, while salts precipitated at the bottom of the lake.     

Holocene environmental changes as recorded by mineral magnetism of sediments from Anguli-nuur Lake,southeastern Inner Mongolia Plateau,China

Two cores, one 1141-cm long (An-S) and the other 885-cm long (An-A), were retrieved from Anguli-nuur Lake (41°18′–24′N, 114°20′–27′E, ～ 1315 masl), one of the largest lakes in the transition zone between a semi-humid and semi-arid climate parallel to the present limit of the southeast monsoon along the southeastern Inner Mongolia Plateau in north China. Mineral-magnetic parameters (χ_lf, ARM, IRM_300mT, SIRM and IRM_? 300mT) were measured on An-S and two additional parameters (χ_ARM and HIRM) and four inter-parametric ratios (χ_ARM/SIRM, IRM_300mT/SIRM, IRM_? 300mT/SIRM and SIRM/χ_lf) were calculated. Potential sources of these lake sediments (catchment soils and dune materials close to the lake and in a distant sand plain) were sampled, and the magnetic properties of the surface-material specimens were measured. A chronological model was developed for An-S by comparing and combining AMS¹⁴C dates of An-S with ¹³⁷Cs, ²¹⁰Pb and AMS¹⁴C dates of An-A. With the help of surface-material magnetism, the magnetic data of An-S in combination with particle size, TOC and C/N and pollen analyses indicate the environmental changes during the last ～ 10,000 years around this lake. Conditions began to ameliorate at 10,900 cal. yr BP (9600 ¹⁴C yr BP) and thus relatively wet and warm environments prevailed during 10,900–8900 cal. yr BP (9600–8000 ¹⁴C yr BP). The Holocene optimum or the wettest and warmest conditions, was during 8900–7400 cal. yr BP (8000–6500 ¹⁴C yr BP). The environment began to deteriorate from 7400 cal. yr BP (6500 ¹⁴C yr BP) and the driest and coolest conditions occurred during 2200–480 cal. yr BP. There may have been a minor amelioration after 480 cal. yr BP. The inferred changes in palaeoenvironmental conditions around Anguli-nuur Lake are broadly in agreement with those around most other sites on the Inner Mongolia Plateau.     

An example of the consequences of human activities on the evolution of subalpine landscapes

A pollen study at Survilly (2235m asl, 06° 49′ 12″ E, 45° 59′ 24″ N), a small peatbog located on the Anterne mountain (Upper-Arve Valley, French north-western Alps) highlights the local role of human activities in Holocene vegetation dynamics of the currently treeless subalpine belt and the consecutive resumption of erosion. As early as 8890 cal. years BP (± 122), Pinus cembra grew close to the site. Grasslands without shrubs were established at around 4624 ± 86 cal. years BP. Due to human activities, spruces extended little after 3600 cal. BP. The intense grazing that resulted in the current alpine meadows goes back to 1436 cal. years BP (± 81). After 4624 cal. BP three clay layers show that from this period, the erosion became as active as during the first steps of the colonization of the vegetation prior to 10,050 cal. BP. During peat growth only a millimetre of clay at the end of the 9400–9050 cal. BP climatic event was recorded.     

Revised paleoenvironmental analysis of the Holocene portion of the Barbados sea-level record: Cobbler’s Reef revisited

Sample elevations corrected for tectonic uplift and assessed relative to local modeled sea levels provide a new perspective on paleoenvironmental history at Cobbler’s Reef, Barbados. Previously, ¹⁴C-dated surface samples of fragmented Acropora palmata plotted above paleo sea level based on their present (uplifted) elevations, suggesting supratidal rubble deposited during a period of extreme storms (4500–3000 cal BP), precipitating reef demise. At several sites, however, A. palmata persisted, existing until ~370 cal BP. Uplift-corrected A. palmata sample elevations lie below the western Atlantic sea-level curve, and ~2 m below ICE-6G-modeled paleo sea level, under slow rates of sea-level rise, negating the possibility that Cobbler’s Reef is a supratidal storm ridge. Most sites show limited age ranges from corals likely damaged/killed on the reef crest, not the mixed ages of rubble ridges, strongly suggesting the reef framework died off in stages over 6500 yr. Reef crest death assemblages invoke multiple paleohistoric causes, from ubiquitous hurricanes to anthropogenic impacts. Comparison of death assemblage ages to dated regional paleotempestological sequences, proxy-based paleotemperatures, recorded hurricanes, tsunamis, European settlement, deforestation, and resulting turbidity, reveals many possible factors inimical to the survival of A. palmata along Cobbler’s Reef.

     

Evidence of high-energy events in the geological record: Mid-holocene evolution of the southwestern Doñana National Park (SW Spain)

Four phases are distinguished in the Mid-Holocene evolution of the southwestern Doñana National Park (SW Spain), based on the multidisciplinary study of sediments in drill cores. In the oldest phase (> 5500-5400 cal. years BP), a coastal, brackish lagoon occupied the central part of the study area, partly enclosed by the Doñana spit and limited by fluvial levees. An evolution from subtidal to intertidal conditions characterized the areas located close to the inner side of the Doñana spit during the same phase. The following phase (∼5400-5200 cal. years BP) is characterized by a high-energy event (tsunami?), which caused the breakthrough of the Doñana spit and the creation of new littoral strands in the inner areas. In the first period of the third phase (∼5200-4200 cal. years BP), estuarine infilling was probably the dominant process, with the accumulation of phyllosilicate-rich clays in the lagoon bed. This was followed by a renewed phase of instability (∼4200-4100 cal. years BP) indicated by the presence of fine storm-lain deposits and thicker, probably tsunami-induced shelly deposits. The last phase (∼4100-3700 cal. years BP) comprises: a) an infilling period, with a diminution of the marine influence; and b) two new high-energy events, which caused the erosion of the Doñana spit and the creation of new cheniers.In the last 7000 years, the comparison of these results with a revision of both geological and historical records has revealed the occurrence of twenty tsunamis (at least) during this period in Portugal and southern Spain. Evidences of these high-energy events are washover fans, bioclastic coarse-sized layers within salt marsh deposits or the presence of giant boulders and pebbles. The determination of the recurrence period is very difficult owing to the very scarce data, although our data and other authors do not discard a possible periodicity of 2000 years for a cycle of two events separated by 300-400 years.     

Cooling in the Gulf of St. Lawrence and estuary region at 9.7 to 7.2 C ka (11.2-8.0 cal ka): Palynological response to the PBO and 8.2 cal ka cold events, Laurentide Ice Sheet air-mass circulation and enhanced freshwater runoff

An examination of post-Younger Dryas (YD) pollen stratigraphies in the Gulf of St. Lawrence and St. Lawrence estuary region reveals features in the pollen records that represent breaks in the normal vegetation succession, widespread vegetation suppression, and a delay in migration of plant taxa between 9.7 and 7.2 ¹⁴C ka (11.2 and 8.0 cal ka). The domination of Alnus crispa at sites bordering the St. Lawrence estuary-Gulf region in Gaspésie and northern New Brunswick within this timeframe represents a diversion from the typical vegetation progression from Picea and/or Populus or Picea/Betula to Pinus and/or Betula, and signifies a shift to a cooler, drier climate. Coinciding with the A. crispa expansion and domination in that region was the contraction of Picea populations in other areas. In southwestern New Brunswick and eastern and southeastern Nova Scotia, Picea was replaced by the first appearance of tree birch, B. papyrifera; whereas in western and southwestern Newfoundland, Picea gave way to a resurgence of shrub birch, Betula glandulosa. The Picea contraction and immediate resurgence of Betula represents cooling, and is reliably dated at 9720 ± 110 ¹⁴C BP (10,800-11,240 cal BP) in southwest Newfoundland. This first post-YD episode of widespread cooling is correlated with the North Atlantic Preboreal Oscillation (PBO) centered around 9650 ¹⁴C BP (10,900-11,180 cal BP) in the adjacent Great Lakes region. Sites exposed to winds from the Gulf of St. Lawrence in eastern New Brunswick, Prince Edward Island, and northern Nova Scotia show a lingering persistence of Picea and delay in arrival of Pinus to 8.0 and 7.7 ¹⁴C ka (9.0 and 8.4 cal ka), yet Pinus was dominant as early as 9.4 ¹⁴C ka (10.6 cal ka) in southwestern New Brunswick. At the same time, tundra vegetation persisted at high elevations in western and southwestern Newfoundland only to be replaced by upslope migration of shrub-birch heath by 8 ¹⁴C ka. Prolonged broad-scale cooling to 8 ¹⁴C ka and to as late as 7.7 ¹⁴C ka extended up to 200 km inland in areas exposed to the St. Lawrence estuary and Gulf region and was in response to strong, cold, dry anticyclonic winds coming off the retreating Laurentide Ice Sheet in combination with enhanced freshwater runoff through the Gulf of St. Lawrence.The end of the period of prolonged cooling and onset of regional warming coincided with the diversion of western Canada runoff and Agassiz-Ojibway drainage to Hudson Bay and reduced effect or final break-up of the Laurentide Ice Sheet. Several sites document a subsequent cold shift, that interrupted regional warming at 7650 to 7200 ¹⁴C BP (8400 to 8000 cal BP), and which is variously represented by the suppression of Pinus and resurgence of Picea, sometimes with A. crispa (Québec-Maritime region), or by an abrupt decrease of Picea and resurgence of Betula (western Newfoundland). This second post-YD cool interval is equated with the 8200 cal BP cold event registered in the Greenland ice isotopic record.     

Évolution du trait de côte à l’Holocène supérieur dans la Sebkha El-Guettiate de Skhira (Golfe de Gabès, Tunisie) à travers sa faune d’ostracodes et de foraminifères

A 122 cm-long core was taken in the El-Guettiate Sebkha of Skhira (southeastern part of Tunisia) in order to investigate the recent palaeoenvironmental evolution of this region. The quantitative and qualitative analysis of ostracod and benthic foraminifera assemblages coupled with a correspondence analysis allows the reconstruction of palaeoenvironmental changes during the Holocene in this area. Four typical associations of ostracods (open marine, coastal marine, lagoonal and estuarine brackish) and two associations of benthic foraminifera (coastal and lagoonal) were distinguished. The onset of restricted lagoonal environments linked to the building-up of sand spit led to the onset of restricted lagoon and brackish environment at cal. 5408 years BP. The Shannon and equitability index of diversity were used to decipher the structural variations of the populations of ostracods and benthic foraminifera along the sampled core. We note a reduction in the Shannon index from the bottom to the top, which indicates a progressive isolation of the biotope. The open lagoonal episode is characterized by high values of diversity. During restricted lagoonal episodes the Shannon and equitability index are reduced. The correspondence analysis reveals an environmental gradient related to the marine influence. It shows an antagonism between the widely opened estuarian lagoonal species and those of restricted lagoon. The less opened estuarian lagoonal taxa occupy an intermediate position. Based on these evidences, microfauna carried out in the El-Guettiate Sebkha allows us to recognize four phases beginning with a widely opened estuarian lagoon (ca. cal. 7460 years PB), followed by a restricted lagoon (ca. cal. 5408 years BP) and finally a brackish lagoon evolving towards the present-day sebkha environment. The opened estuarine lagoon is characterized by high values of species richness and diversity indices.     

Glacial-interglacial changes in moisture balance and the impact on vegetation in the southern hemisphere tropical Andes (Bolivia/Peru)

A palynological investigation of the last glacial-interglacial cycle in the southern hemisphere tropical Andes reveals changes in the moisture balance as the main driver in vegetation change. Thirty accelerator mass spectrometry radiocarbon dates, biostratigraphy and tephra correlation reveal that a 119 m sediment core recovered from the Huiñaimarca sub-basin of Lake Titicaca (16.0° to 17.5° S, 68.5° to 70° W; 3810 masl) contains sediments covering > 151,000 years. Correlation of aridity indicators with precessional variations in insolation is used to fine tune the structure of the age-depth curve within this period.Variations in Isoëtes concentration (above/below 10,000 grains/cm³) identify the extent of shallow water environments. Examination of another palaeolimnological indicator (Pediastrum) and consideration of the bathymetry of the Huiñaimarca sub-basin allow the reconstruction of lake-level fluctuations. These data indicate five wet/dry cycles between c. 151,000 and 14,200 cal yr BP. High stands are suggested during the transition into (c. 134,000 cal yr BP), and out of (c. 114,000 and 92,000 cal yr BP), the last interglacial, and during full glacial conditions (c. 70,000 and 45,000 cal yr BP). These cycles are superimposed on a general trend of deepening lake levels through the glacial period.This interpretation is supported by correlation with sediments from Salar de Uyuni (20°S, 68°W; 3653 masl). The youngest wet episode is concurrent with palaeolake Minchin (c. 45,000 cal yr BP), with further evidence for an additional wet period commencing c. 28,000 cal yr BP, concomitant with palaeolake Tauca. The timing of lake level fluctuations is also supported by palaeoshoreline reconstructions from the Uyuni-Poopó region. However, our data do not suggest a major peak in lake level in Huiñaimarca during the Ouki lake cycle (c. 120,000–98,000 cal yr BP) as inferred from U–Th ages obtained from palaeoshorelines around Lago Poopó. The most extreme dry event occurs during the last interglacial period and resulted in a sedimentary hiatus tentatively dated to c. 121,000–129,000 cal yr BP.The observed wet/dry cycles are shown to have a marked and rapid impact on the vegetation. The aridity of the last interglacial promoted a community dominated by Chenopodiaceae/Amaranthacae, with no modern Andean analogue. Polylepis/Acaena pollen is also shown to fluctuate markedly (0–20%), particularly during the transitions into, and out of, the last interglacial. It is probable that this pollen taxon is primarily representative of the high altitude arboreal genus Polylepis, which is a key component of highly biodiverse Andean woodlands today. Rapid fluctuations indicate the sensitivity of this ecosystem to natural environmental pressure and potential vulnerability to future human impact and climate change.The 100,000 year (eccentricity) solar cycle is shown to be the major controlling factor in moisture balance and vegetation over the last glacial-interglacial cycle. However, significant fluctuations in moisture balance are also evident on timescales considerably shorter than the full glacial-interglacial cycle. We have linked these to precessional (21,000 year) forcing. Nevertheless, precise independent dating during the full glacial cycle is required to confirm the importance of this forcing mechanism.     

Palaeoecological evidences from foraminifers and ostracods on Late Quaternary sea-level changes in the Ombrone river plain (central Tyrrhenian coast,Italy)

The multidisciplinary study of borehole Ombrone S1, sampled in the Grosseto plain, near the Ombrone river mouth, provides new data about sea-level changes during the Holocene in central Tyrrhenian Sea. The palaeontological analysis of the borehole highlights data concerning the foraminifers and ostracods useful to the palaeoenvironmental interpretation. Moreover, geochemical analyses (δ¹³C and δ¹⁸O) were performed on Ammonia parkinsoniana tests and Cyprideis torosa valves. Integrating the results of the palaeontological, lithological and geochemical data, it is possible to single out the environments related to the transgressive trend. Borehole Ombrone S1 is characterised by basal deposits of continental settings, which includes some brackish water marsh, may be related to a slight sea-level oscillation, followed by fluvial gravel ones testifying the deltaic progradation of the Palaeo-Ombrone river. Above, two distinct trangressive events, which were divided by a phase of still-stand, took place. The first one, above the gravel, was responsible for the establishment of the brackish water conditions due to the presence of a barrier-lagoon system, which was finally filled up by terrigenous input. The second one produced, at first, lagoon settings near the sea and, successively, deltaic-related settings for the submersion of the barrier. The littoral sandy bar at 10 m of core-depth represents the first sure evidence of the alluvial plain progradation, which develops up to the core-top.     

Mid to Late Holocene palaeoenvironment of Lake Eastern Juyanze (north-western China) based on ostracods and stable isotopes

An exposed section of nearly 13 m thick was investigated in the ancient depression of Lake Eastern Juyanze, north-eastern China. The succession of lacustrine and aeolian deposits covers a period from about 5400 to 2700 cal. a BP as indicated by four radiocarbon ages of macro-plant debris. Fifteen ostracod taxa were identified of which Limnocythere inopinata and Darwinula stevensoni are by far the most abundant species. Stable isotope (O, C) data of ostracod calcite as well as ostracod species abundances and X-ray diffraction results of bulk sediment samples were used to reconstruct the history of Lake Eastern Juyanze. Highest lake levels (water depth ∼10 m) occurred between 5100 and 4100 cal. a BP and were succeeded by intermediate and low levels until about 3150 cal. a BP. Three short-term events of complete desiccation were recorded between 3150 and 2900 cal. a BP. The lake experienced relatively high levels again for some decades at about 3000 cal. a BP and for at least two centuries after 2900 cal. a BP. According to the ostracod and gastropod record and the high abundance of a large diatom (Campylodiscus clypeus) in the lake sediments oligohaline to slightly mesohaline conditions were reconstructed for most of the lake periods (4-6 g/l). Geochemical and palaeontological records of Lake Eastern Juyanze reveal the retreat of the Asian monsoon after China’s Hypsithermal culminating in climate instability at about 3000 cal. a BP.     

Palynological evidence for Holocene environmental change in the Changjiang (Yangtze River) Delta, China

Holocene vegetation changes in response to climate fluctuations and human impacts are reviewed on the basis of pollen analyses from borehole cores taken from the Changjiang (Yangtze River) delta, China, and other previously reported data. During the earliest Holocene (10,930−9000 cal yr BP), the climate was warm and wet, allowing thermophilous hardwoods to occupy mid- and low-elevations surrounding a palaeo-Changjiang estuary. The climate became gradually cooler, and cool-tolerant conifers, grasses and ferns became dominant until 7600 cal yr BP, when the estuary became a delta. A mid-Holocene climatic optimum occurred between 7600 and 4800 cal yr BP, when evergreen and broadleaved deciduous trees flourished at mid- and low-elevations surrounding the delta front-prodelta. After this time, climate became cooler again until 1340 cal yr BP. During this period, evergreen and broadleaved deciduous trees were replaced by conifers and grasses inhabiting the inter/subtidal flat-delta front. This development of conifer-grassland vegetation was shortly interrupted between 3860 and 3200 cal yr BP when thermophilous tree cover increased and open vegetation with scattered conifers was reduced. Since 1340 cal yr BP, the vegetation has been similar to that at present under warm, wet conditions. Human impacts are recognized by the first appearance of Fagopyrum and a sudden increase in herb pollen at 4500 and 1340 cal yr BP, respectively.     

A new well-preserved ostracod fauna from the middle Burdigalian (lower Miocene) of the North Alpine Foreland Basin

The marine middle Burdigalian sediments of the North Alpine Foreland Basin (NAFB) or Molasse Basin are well known for abundant occurrences of benthic foraminifers and ostracods. However, taxonomic studies of ostracod assemblages are comparatively rare and, given its abundance, the group remains heavily understudied. Here we report a new, rich and well-preserved ostracod fauna from the middle Burdigalian Neuhofen Formation at Mitterdorf, in the northeastern part of the NAFB. The material comprises a total of 3029 ostracod specimens. We identified 44 species; all species are described and, with one exception, illustrated. Our material reveals the presence of 17 ostracod species that were previously unknown from the middle Burdigalian in the NAFB, i.e., Cytherella aff. vulgatella, Cytherella aff. méhesi, Bairdoppilata aff. subdeltoidea, Paranesidea? sp., Paracypris aff. aerodynamica, Parakrithe dactylomorpha, Pseudopsammocythere sp., Callistocythere daedalea, Costa aff. reticulata, Ruggieria aff. longecarenata, Heliocythere aff. vejhonensis, Heliocythere sp., Loxocorniculum hastatum, Neocytherideis cypria, Cytheretta cf. tenuipunctata dentata, Cytheropteron cf. ruggierii, and Semicytherura resecta. The palaeobiogeography of the ostracods indicates a relatively open marine Burdigalian connection between the NAFB and the Mediterranean Sea, in agreement with previous work. Our data also suggest that a significant degree of endemism existed in the middle Burdigalian sea of the NAFB, of which previous studies yielded only sparse signs. Moreover, our results indicate that some ostracod species survived the late Burdigalian sea retreat from the NAFB by dispersing eastward into the adjacent regions (Vienna Basin, Carpathian Foredeep), where marine conditions still prevailed. A compilation of all known middle Burdigalian ostracod faunas from the NAFB documents a high species diversity, with over 120 species. Their spatial distribution, with many species being restricted to a single site, suggests heterogenous microhabitats, possibly influenced by small-scale differences in water depth, nutrient availability and oxygenation.     

Composition and Distribution of Recent Marine Ostracod Assemblages in the Bottom Sediments of Central Aegean Sea (SE Andros Island,Greece)

The present study provides a thorough analysis of the composition of recent marine ostracod populations from the bottom sediments of the central Aegean Sea, as well as their distribution patterns. In particular, a detailed qualitative and quantitative study of living ostracod assemblages was carried out in the marine environments of SE Andros Island. Sampling took place at Kastro and Korthi Gulf, both located at the southeastern coast of the Andros Island and from depth of 1.5 to 18 m, while additional samples were collected outside the gulfs at a depth of 120–180 m. Only ostracods considered to have been living at the time of collection were picked from the samples. A total of 51 species belonging to 34 genera were identified and four main ostracod assemblages, representing different biotopes, were distinguished. The results produced from the application of Q‐mode cluster analysis in the data set, the calculated assemblage structure indices for each sample, as well as the bathymetric and granulometric data are as follows: Hiltermannicythere rubra assemblage (occurs in substrates of sandy mud and at a water depth ranging from 40–60 m to the depth of 100 m or even more), Loxoconcha affinis, Xestoleberis sexmaculata assemblage (occurs in substrates of muddy very fine to fine sands and shallower environments), Semicytherura incogruens assemblage (occurs in very fine sands at a water depth from 10 to 28 m), Loculicytheretta pavonia and Neocytherideis fasciata, Pontocythere turbita assemblages (occurs mainly in fine sands and at a water depth between 3.5 and 15 m) and Urocythereis neapolitana assemblage (occurs in substrates of medium to coarse sand and at a water depth of less than 20 m). (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Assessing surficial foraminiferal distributions as an overwash indicator in Sur Lagoon,Sultanate of Oman

The identification of tsunami and storm deposits in arid coastal environments can be problematic, as overwash sediments may not show significant contrasting lithologic characters with lagoonal sediments. In this study foraminifera were evaluated as an overwash indicator in a small (12 km²) intertidal lagoon located at Sur, in the Sultanate of Oman. The lagoon is shallow (< 5 m depth), tidally-controlled and communicates with the open sea through a narrow subtidal entrance channel. The lagoon is largely composed of intertidal sand and mudflats with fringing mangroves. Previous work at Sur identified evidence for overwash deposits associated with the 28 November 1945 Makran Trench tsunami (M_w 8.1) which were identified based on the presence of a laterally extensive shelly bed with distinctive taphonomic characters. In this study, particle size, stable isotopic and foraminiferal (taxa and taphonomy) analyses were conducted on surface sediment samples from Sur Lagoon to determine modern spatial trends in the lagoon for future comparison with overwash sediments deeper in the geologic record. Q-mode cluster analysis of the foraminiferal data (n = 54) found three main biofacies which follow lagoon sub-environments: Shallow Marine Area, Main Lagoon Basin, and Distal Lagoon Basin. The Shallow Marine Area is mainly subtidal with higher wave energy, the Main Lagoon Basin is predominantly intertidal with moderate wave energy, whereas the Distal Lagoon Basin is isolated and mainly intertidal with low wave energy.The most useful parameters for assessing overwash events in Sur Lagoon are the foraminifera taxa rather than the taphonomic characters themselves. The most useful taxa for recognizing an overwash (e.g. tsunami or storm) will be the abundance of Amphistegina spp., Ammonia inflata, Elphidium advenum and planktics which are predominantly found in the Shallow Marine Area. The abundance trend of these species with distance into the lagoon has an inverse relationship with higher r² values than the other taxa. Taphonomically there is a predominance of larger specimens in the Shallow Marine Area along with a higher abundance of fossil specimens.     

Palynological record of climate change during the last deglaciation from the Song Hong (Red River) delta, Vietnam

The palynological sequence from core ND-1 on the Song Hong delta in the northern Vietnam reveals the climate change during the last deglaciation. The identified pollen in the core is dominated by Castanopsis (Lithocarpus), Elaeocarpus, Ficus, Piperaceae and Quercus. High percentages of temperate taxa including the conifers Dacrydium, Podocarpus, Pinus, Cupressaceae, Txodiaceae and Cryptomeria, and broad-leaved taxa of Carpinus, Alnus, Juglans, Carya, Ulmus, Fagus, Ilex, Castanea, Quercus, which have a mainly upland distribution, is possibly associated with a lowering of the montane vegetation boundary. On the other hand, intensified river influence can also result in an increase in the temperate allochthonous taxa. After analyzing the magnitude of river influence on pollen assemblages during the sedimentary environment evolution, we extracted the climate information and used this to reconstruct climate change during the last deglaciation. A cooler climate during 14.5-10.9 cal. kyr BP than at present is indicated by higher percentage of temperate types than at present under a similar river influence on the floodplain. The Younger Dryas cooling event is recognized by widely developed grasslands between 12.9 and 11.6 cal. kyr BP, adding to the evidences for this period from both terrestrial and marine records in regions influenced by the East Asian monsoon. Two other cooling periods, 9.4-9.0 cal. kyr BP and 6.5-5.2 cal. kyr BP, are indicated by increases of temperate pollen taxa such as Cryptomeria, Alnus, Quercus, and Castanea.     

Macrophytes in the anthropic constructions of the Venice littorals and their ecological assessment by an integration of the “CARLIT” index

A check-list of the macroalgae which colonize the artificial structures “dykes” formed by limestone blocks, placed between the northern Adriatic Sea and the Venice Lagoon to protect the wide sea inlets of Lido and Malamocco, the stone breakwaters and the submerged reefs parallel and perpendicular to the sea coastline of the Lido island “Murazzi” is presented. Macroalgae have been sampled monthly during one-year period (February 2007–January 2008) both in the lagoon inlets and along the marine coast. Flora was represented by 213 taxa: 61 Chlorophyta, 114 Rhodophyta, 38 Ochrophyta (37 Phaeophyceae, 1 Xanthophyceae), with the richest and luxuriant vegetation in the lagoon inlet areas. The application of the Rhodophyta/Chlorophyta (R/C) index and the Expert-Macrophyte Quality Index (E-MaQI) highlighted the “High” ecological status (EQR > 0.9) of the lagoon inlet areas.As E-MaQI is not applicable in marine areas, an adaptation of CARLIT to the anthropic structures of the north-western coasts of the northern Adriatic Sea and its integration with the dominant taxa is proposed.The application of the revised index to the Lido dykes and breakwaters placed along the marine littorals shows “Moderate” conditions.     

Estudio paleoecológico de Foraminíferos de testigos del Holoceno de Golfo Nuevo (Patagonia, Argentina)

A micropaleontological study (Order Foraminiferida) was conducted on two Holocene cores from Golfo Nuevo (Patagonia, Argentina). The most abundant species are Buccellaperuviana f. campsi (Boltovskoy) and Bulimina patagonica (d’Orbigny), suggesting an inner-shelf environment. Qualitative and quantitative analyses indicate the paleoecological and paleoenvironmental variations along cores. A transition from normal marine conditions of the inner shelf during the Middle Holocene (ca. 8160-7700 years B.P.) to marginal marine conditions in the Late Holocene (ca. 1890 years B.P.) is inferred. This transition was accompanied by lower oxygen levels than the current values in Golfo Nuevo. These variations may have been due to an increase in precipitation near the study zone and a rise in sea level caused by an improvement in the climatic conditions related to the Climate Optimum (ca. 7000 years B.P.). These new conditions of higher temperature and lower salinity of the surface waters may have hindered deep-water renewal, producing a change in the circulation dynamics of the gulf and causing a reducing environment.