Sedimentary Assemblages Research Articles

Cladocera biodiversity in La Tembladera Lake (Ecuador): a palaeolimnological approach

Cladocera (Crustacea: Branchiopoda) biodiversity was examined in sediment assemblages in La Tembladera Lake, on the southern coast of Ecuador. We found remains from 14 Cladocera taxa belonging to three families: Sididae, Daphnidae and Chydoridae. One taxon is planktonic (Ceriodaphniaspp.) and 13 taxa are littoral (Sarsilatonaserricauda,Chydorussp.,Dunheveniasp.,Leberissp.,Alonasp.,Magnospina dentifera,Kurziasp.,Acroperus tupinamba,Camptocercussp.,Oxyurella longicaudis,Leydigiopsissp.,Euryalonasp. andNotoalonacf.sculpta). Descriptions and pictures of the remains were included in this article to help palaeolimnologists identify tropical cladoceran remains in the sediment. These results enlarge the crustacean biodiversity data for dry tropical forests in South America and help to constrain our understanding of their geographical distribution. Further studies should focus on capturing living cladocerans to make identifications at the species level and to help interpret the sedimentary signal using ecological data.

SPATIO-TEMPORAL RESPONSE OF SEDIMENTARY DIATOMS TO WATER LEVEL IN A SHALLOW LAKE

In recent years, human activities have resulted in variations of hydraulic conditions in shallow lakes, thereby affecting interactions between environmental variables and aquatic plants. This feedback of plants on environmental changes is largely recorded in lake sediments. In this study we collected surface sediments in different seasons and a sediment core from a shallow lake Baiyangdian. We investigated the seasonal effects of water level and six physicochemical variables in surface sediments, as well as their impacts on the distribution of diatom assemblages. Therein the response of diatom assemblages to water level and the spatio-temporal effects of water level are highly emphasized. Results indicate that water level significantly changes between seasons, however there is no significant seasonal effects for the com- position of grain size. The lake productivity increases with the vigorous growth of aquatic plants. Water level largely determines the distribution of diatom assemblages in surface sediments and the sediment core. Spatial isolation causes the difference between the habitats and alters the relation between water level and diatom taxa. Human activities also affect the relevance of water level with diatom assemblage. The results can provide the helpful information for the local water resource management.

A Compositional Classification For Grain Assemblages In Fine-Grained Sediments and Sedimentary Rocks—Reply

Abstract A tripartite compositional classification is proposed for sediments and sedimentary rocks that have grain assemblages with greater than 50 percent of a weight or volume of particles smaller than 62.5 µm (4 Phi). Tarl (terrigenous–argillaceous) contains a grain assemblage dominated by more than 75 percent of particles of extrabasinal derivation, including grains derived from continental weathering and also volcanogenic debris. Carl (calcareous–argillaceous) contains less than 75 percent of particles of extrabasinal derivation debris and among its intrabasinal grains contains a preponderance of biogenic carbonate particles including carbonate aggregates. Sarl (siliceous–argillaceous) contains less than 75 percent of particles of extrabasinal derivation and contains a preponderance of biogenic siliceous particles over carbonate grains. These three classes of fine-grained particulate sediments and rocks effectively separate materials that have distinct depositional settings and systematic contrasts in organic-matter content and minor grain types. In the subsurface the grain assemblages that define these classes follow contrasting and predictable diagenetic pathways that have significant implications for the evolution of bulk rock properties, and thus, assigning a fine-grained rock to one of these classes is an important first step for predicting its economic and engineering qualities. For purposes of description these three class names can be joined to modifier terms denoting rock texture, more precise compositional divisions, specific grain types of notable importance, and diagenetic features.

Extant coccolithophores from the western equatorial Indian Ocean off Tanzania and coccolith distribution in surface sediments

Living coccolithophores and coccoliths from surface sediments were investigated in the western equatorial Indian Ocean off Tanzania, from the coast and Pemba Channel to the open ocean. In total, 49 plankton samples from 8 stations and 20 surface sediment samples collected in February 2008 were analysed. Coccolithophore standing stock ranged from barren up to almost 23,000 coccospheres/l in the upper water column and the living community comprised 47 different taxa in total. In addition, six more species were only found as detached coccoliths. Coccolithophore numbers were generally low and only Florisphaera profunda, Gephyrocapsa oceanica, and Emiliania huxleyi were numerically important (>5,000 coccospheres/l). Two distinct depth-related assemblages were identified. The upper photic zone (down to about 50m) in the Pemba Channel was dominated by G. oceanica and can be related to slightly increased nutrient conditions. In contrast, the upper photic zone community in the open ocean (down to about 70m) is characterised by high numbers of Umbellosphaera irregularis, typically indicating oligotrophic stratified waters, high sea-surface temperatures and strong water stratification. The lower photic-zone flora in the whole study area is generally dominated by F. profunda and accompanying species. A total of 40 species were identified in the surface sediments and total coccolith numbers vary drastically from <1000 to 18,200 x 106 coccoliths/g of sediment. The absolute numbers are much lower near-shore and strikingly enhanced further offshore mainly due to heavy dilution by fine-grained terrigenous sediments. Nevertheless, the occurrence of species in the plankton communities compares well to those of the surface sediment assemblages although plankton samples are from just one season. This points to an excellent preservation potential in this area, which can be explained by high supply of clay-rich sediments and a therefore rapid burial of the coccoliths in shelf and upper slope sediments.

Enigmatic ridges in Lake Vättern, Sweden

The latest generation of high-resolution multibeam sonars reveal ever smaller subaqueous landforms, particularly in shallow marine and lake environments. High-resolution bathymetric data from the floor of Lake Vattern, Sweden, reveal fine-scale landforms on a bouldery sediment surface, which we attribute to ice-related processes. We explore subglacial, grounding-zone, crevasse infill and push/scour processes of grounded and floating ice in an attempt to explain the origin of these enigmatic features. Lake Vattern in south-central Sweden is a deep, elongate rift basin which lies amid regional landform and sediment assemblages produced during the retreat of the last Fennoscandian Ice Sheet (FIS). The regional retreating ice margin terminated in the large proglacial Baltic Ice Lake, to which the Vattern Basin was connected before its eventual drainage (Lundqvist & Wohlfarth 2001). A recent high-resolution multibeam survey of sectors of the Vattern lake floor revealed landforms associated with marginal ice grounding and retreat. On a mid-lake shoal at 30–40 m depth, a suite of fine-scale, enigmatic landforms have been formed in stiff sediment (Fig. 1). Fig. 1. ( a ) Multibeam bathymetry from Lake Vattern showing 1–2 m amplitude sediment ridges that are formed on a shoal, which comprise both parallel, linear components (L, L*) and sinuous ridges (S, S*) of …

Comparison of living and surface sediment coccolithophore assemblages in the Pacific sector of the Southern Ocean

This study examined recent coccolith surface sediment assemblages across the Pacific sector of the Southern Ocean (from Punta Arenas, Chile to Wellington, New Zealand). Twenty five stations located within 44.4°S to 65.4°S and 80.1°W to 174.5°E were selected in order to assess if and how the surface sediment assemblages reflect the present-day coccolithophore community and surface- water oceanographic conditions. The highest numbers of coccoliths in the surface sediments are reached near the East Pacific Rise and close to the Subtropical Front, at the New Zealand Margin (>6x109 coccoliths/g of sediment). The dominant taxa are Emiliania huxleyi (including types A, B, B/C and C), Calcidiscus leptoporus, Gephyrocapsa spp. (including G. muellerae, G. oceanica and G. ericsonii), Umbellosphaera tenuis and Coccolithus braarudii. Despite the recognition of species morphotypes being hampered by carbonate dissolution at some locations, we observed that numbers generally decrease southward until almost a monospecific and sporadic record of E. huxleyi (types B/C and C) and C. leptoporus south of the Polar Front occurs. The recent coccolithophore distribution was compared to already published living coccolithophore distributions (i.e., water column samples collected at the same specific locations) showing a fairly similar pattern. Combining the numbers of cells/l and coccoliths/g of sediment, different coccolithophore assemblages were established coincidentwith areas bounded by the major surface oceanographic fronts, i.e. the Subantarctic Zone and the Polar Front Zone.

Distribution of heavy and clay minerals in coastal sediment of Jijel, East of Algeria: indicators of sediment sources and transport and deposition environments

The identification of bulk, clay (<2 μm), and heavy (63–200 μm) minerals has been investigated on 42 coastal samples along the Jijel bay (Eastern Algeria). The mineralogical assemblages are used to identify the mineral sources and to interpret the mineral distribution. The samples were subjected to grain-size analysis by sieving and by X-ray diffraction on powder (bulk mineralogy) and on oriented aggregates (clay fraction). The bulk fraction is composed by muscovite, plagioclase, calcite, anhydrite, clay fraction, and a predominance of quartz (11 to 45 %). Clay fraction is composed of kaolinite, chlorite, smectite, interstratified minerals, and a predominance of illite (43–65 %). In addition, the heavy minerals assemblages of sediments have been identified by binocular observation, X-ray diffraction, and optical microscope. The heavy minerals are dominated by opaque minerals (16–65 %) associated with variable proportions of muscovite, chlorite, kyanite, sillimanite, biotite, pyroxene, amphibole, garnet, epidote, zircon, tourmaline, and rutile. Both fluvial hydrodynamic and marine agents control the sediment distribution along the coast. Indeed, the passage from areas in accretion toward those in erosion has caused a concentration in heavy minerals on coastal sections in recession; however, the light minerals were moved selectively toward accretional areas. The heavy mineral assemblages present in rivers sediment indicate that they were delivered to the coast in a highly selective manner. This assemblage of heavy mineral is also present with high concentration in a variety of fluvio-marine environments such as river mouths, coastal dunes, and beaches. These sediments are derived from the various geological formations (metamorphic formations of the basement, magmatic rocks, and other sedimentary rocks) observed in the watershed.

Characterizing bacterial assemblages in sediments and aerosols at a dry lake bed in Australia using high-throughput sequencing

Dust storms are responsible for the transport of a large quantity of bacteria from arid regions. A severe drought in the first decade of the new millennium in Australia increased the incidence of dust transport further. The major aims of this study were to characterize the bacterial communities in aerosols and their associated source sediments using high-throughput sequencing (HTS) and to investigate the possibility of using HTS to link dust to its source, which has not been previously performed in this way. Four field campaigns were conducted at the recently evaporated saline playa Lake Gnarpurt in the Australian state of Victoria between 2008 and 2010 (3 in the austral summer, 1 in winter) to collect aerosol and sediment samples. Aerosol samples were collected on filters up to 150 m above the lake bed using a tethered helium-filled balloon. DNA was extracted from all samples using commercial kits, and the bacterial communities were examined using 454 HTS on the 16S rRNA gene. Over 200,000 sequences from 29 samples were analysed. In both sediment and aerosol samples, Salinimicrobium was the most abundant taxon; however, there was great variation and diversity across all samples. Analysis of similarities of the bacterial communities indicated that there was a significant overlap between the sediment samples and the aerosols collected above that location, showing that the bacteria in the air was derived from a subset of dust from a nearby source. The challenge remains to use bacterial profiling to link an aerosol sample to a distant source.

Spatial distribution of pollen assemblages in surface sediments on the Okhotsk Sea basin floor

オホーツク海の16カ所で採取された海底表層堆積物試料から花粉粒を抽出し，オホーツク海底面における表層堆積物中の花粉群の平面分布を求めた．産出した花粉濃度と花粉出現頻度より，オホーツク海域の花粉群を，海岸から100 km程度までの沿岸域とより遠方の遠洋域の2つに区分した．沿岸域では，トウヒ属・マツ属・カバノキ属・ハンノキ属にモミ属・コナラ亜属・ハシバミ属・ニレ属／ケヤキ属・ツツジ科などが随伴する北方林の組成が特徴で，直近の陸上の植生を適切に反映し，花粉濃度も海底堆積物としては比較的高い値を示していた．これに対して海岸から100 km程度離れた遠洋域では，針葉樹花粉のマツ属やトウヒ属が特に卓越して産出することが特徴であり，花粉濃度も一様に低い値であった．以上より，本論文におけるオホーツク海沿岸域から得られる花粉群は，近傍の陸上植生を適切に反映しており，沿岸流が花粉粒子に及ぼす影響は比較的小さいことが分かった．

Calcareous nannoplankton dating of the Late Quaternary deposits in Greece and the eastern Mediterranean: Case studies from terrestrial and marine sites

The distribution and abundance of Emiliania huxleyi (E. huxleyi) assemblages in the marine sediments of the Aravonitsa Plateau, Greece, and from the eastern Mediterranean are used (1) to evaluate the calcareous nannoplankton NN21a and NN21b biozones and the NN21a/NN21b boundary, and (2) to analyze the palaeoenvironmental and palaeoclimatic conditions prevailing in this interval. The sediment succession displays varied E. huxleyi assemblages and these are interpreted as reflecting climatic variability during marine isotope stages MIS 1–8.

Clay mineral distribution and provenance in the Heuksan mud belt, Yellow Sea

The Heuksan mud belt (HMB), located in the southeastern Yellow Sea, runs parallel to the southwest coast of Korea. In this study, the distribution and relative contribution of four major clay minerals are investigated using 101 surface sediment samples collected in the course of KIOST (2001, 2010, 2011) and KIGAM (2012) cruises, as well as 33 river sediment samples (four from the Huanghe River, three from the Changjiang River, and 26 from Korean rivers) in order to clarify the provenance of fine-grained sediments in the HMB. Based on this currently largest and most robust dataset available for interpretation, the clay mineral assemblages of the fine-grained sediments in the HMB are found to be on average composed of 64.7% illite, 17.9% chlorite, 11.4% kaolinite, and 5.9% smectite. Overall, the clay mineral assemblages are similar in both the northern and the southern parts of the HMB, although smectite seems to be relatively enriched in the southern part, whereas kaolinite is slightly more dominant in the northern part. This clearly indicates that the clays are mostly derived from Korean rivers and, in the southern part of the HMB, partly also from the Huanghe River in China. The new data thus confirm and strengthen the tentative interpretation of some earlier work based on a more limited dataset.

Spatial and Temporal Distribution Differences Among Phytoliths of Phragmites Communis in Northeast China

Phragmites communis phytoliths were extracted from the xerophytic habitat of 12 sampling sites in northeast (NE) China during June–October in 2011 and 2012. The changes of P. communis phytolith concentrations in different temperature zones and growth stages were used to reveal the ecological environmental significance of P. communis phytoliths. The purpose of the study is to provide a scientific reference for quantitative reconstruction of paleoenvironment and studies of phytolith formation. The main phytolith types extracted from the 12 sampling sites and different growth stages were identical; however, the phytolith concentrations differed markedly. In NE China, from the temperate to the warm temperate zone, as temperature increased, the saddle phytoliths, bulliform phytoliths and the silicified stomata concentrations all increased, whereas the lanceolate phytolith concentration decreased. Moreover, in the humid, semi-humid and semi-arid areas, there were different responses of P. communis phytolith concentrations to temperature. Consequently, the spatial results showed that P. communis phytolith concentrations in NE China were closely related to temperature, which enabled inference of the change in temperature from phytolith concentration; however, they were also somewhat affected by humidity. During June–October, the temporal variation results of P. communis phytolith concentrations revealed that there were high lanceolate and bulliform phytolith concentrations in September or October; whereas the saddle phytolith concentration was high in July or August, and the maximum concentration for silicified stomata was in July. These findings may improve the understanding of phytolith formation, and provide useful information to further interpret phytolith assemblages in sediments.

Diatoms in Sub-Surface Sediment Cores from Mangrove Forest Floors of Deltaic Islands in Sundarbans, India

Species constituting diatom assemblages in sediments provide important information regarding the past and present environmental conditions related to soil and water physico-chemistry and also biodiversity dynamics data. This information can reveal the developmental history of the region. Diatoms are sensitive to stochastic changes in the environment, making them extremely reliable bio-indicators. The purpose of the present study was to decipher such biodiversity related information provided by the diatom assemblages from the Indian Sundarbans. Diatoms were identified in the top 50 cm layer of two sediment cores: a newly silted up deltaic landmass with mangroves in early succession stage, and an island within the Protected Area Network with mangroves in late succession stage. Fifteen diatom species, with no past records in the sediments of Indian Sundarbans were identified and described. Four species among them are sporadically mentioned in previous phytoplankton records fi-om the Sundarbans, but these are not confirmed taxonomically. This paper provides identification and nomenclatural notes on all 15 species. High abundance and species richness of the centric forms Coscinodiscus spp., Cyclotella spp., and Thalassiosira spp. at both the sites is attributed to their proximity to estuarine rivers and their regular inundation, leading to settling of planktonic forms within sediment cores. Many pennate forms, namely Amphicampa eruca, Amphora holsatica, Diploneis spp. (except Z). smithii), Epithemia turgida, Eunotiapectinalis, Giffenia cocconeiformis , and Rhaphoneis rhombus which are being reported for the first time fi-om this region have never been part of described planktonic communities in estuarine waters, validating their' soil diatom' status. Typical fi-eshwater diatoms, namely Aulacoseira granulata and Epithemia turgida, in the sediments indicate lower salinity in these areas, not much earlier than present times.

Hydrogeological responses to incoming materials at the erosional subduction margin, offshore Osa Peninsula, Costa Rica

AbstractBulk mineral assemblages of sediments and igneous basement rocks on the incoming Cocos Plate at the Costa Rica subduction zone are examined by X‐ray diffraction analyses on core samples. These samples are from Integrated Ocean Drilling Program Expedition 334 reference Site U1381, ∼ 5 km seaward of the trench. Drilling recovered approximately 100 m of sediment and 70 m of igneous oceanic basement. The sediment includes two lithologic units: hemipelagic clayey mud and siliceous to calcareous pelagic ooze. The hemipelagic unit is composed of clay minerals (∼50 wt.%), quartz (∼5 wt.%), plagioclase (∼5 wt.%), calcite (∼15 wt.%) and ∼30 wt.% of amorphous materials, while the pelagic unit is mostly made up of biogenic amorphous silica (∼50 wt.%) and calcite (∼50 wt.%). The igneous basement rock consists of plagioclase (∼50–60 wt.%), clinopyroxene (∼&gt;25 wt.%), and saponite (∼15–40 wt.%). Saponite is more abundant in pillow basalt than in the massive section, reflecting the variable intensity of alteration. We estimate the total water influx of the sedimentary package is 6.9 m3/yr per m of trench length. Fluid expulsion models indicate that sediment compaction during shallow subduction causes the release of pore water while peak mineral dehydration occurs at temperatures of approximately ∼100°C, 40–30 km landward of the trench. This region is landward of the observed updip extent of seismicity. We posit that in this region the presence of subducting bathymetric relief capped by velocity weakening nannofossil chalk is more important in influencing the updip extent of seismicity than the thermal regime.

Long-term stability of cladoceran assemblages in small, shallow, Canadian Shield lakes experiencing marked calcium declines

A greater appreciation of biotic responses to environmental changes is warranted in small, shallow lakes because of the high number of these habitats, and their unique contributions to regional biodiversity. Furthermore, recent water chemistry monitoring data show that shallow lakes in Ontario are sensitive and have responded significantly to environmental stressors such as acid deposition and lake water calcium decline. Here, we use paleoecological techniques to examine cladoceran assemblages in modern and pre-industrial sediments of 30 shallow lakes to determine the key environmental gradients that influence present-day assemblages, and to assess how assemblage structure has changed since pre-industrial times (pre-1850s). Redundancy analysis of present-day cladoceran assemblages and key environmental variables identified lake surface area and Secchi depth as significant predictors of assemblage composition. In our data set, Secchi depth was not correlated to water clarity but rather to macrophyte cover, suggesting that cladoceran assemblages were highly influenced by habitat structure. In contrast to nearby, deeper lakes, where pelagic cladoceran taxa have changed significantly in relative abundance over time, cladoceran assemblages in present-day and pre-industrial sediments of shallow lakes did not differ significantly in composition. While the specific reasons for this muted response are unknown, we hypothesize that: (1) littoral taxa may be less sensitive to low Ca concentrations, or ecological thresholds have not yet been crossed or are lower for littoral taxa; (2) calcium availability may vary spatially within shallow lakes, and this is not captured in a single measure of water chemistry from the centre of the lake; and/or (3) habitat structure is more important than water chemistry as a predictor of assemblage composition in these study lakes, and this has not changed significantly over time.

Modern pollen assemblages from surface lake sediments in northwestern China and their importance as indicators of vegetation and climate

The modern pollen assemblages of surface lake sediments and topsoils in northwestern China were studied to understand the relationship of modern pollen data with contemporary vegetation and climate, and the differences between the pollen assemblages of surface lake sediments and topsoils. The results show that Chenopodiaceae and Artemisia are dominant elements in the pollen assemblages of northwestern China. Additionally, Ephedra, Cyperaceae, Asteraceae, Poaceae, Picea, Pinus, and Betula are also important pollen taxa. Both pollen assemblages and principal component analysis indicate that pollen data from surface lake sediments and topsoils can be used to differentiate the main vegetation types of this region (desert, steppe, meadow and forest). However, differences exist between modern pollen assemblages of the two types of sediments due to the different relevant source areas of pollen and degrees of pollen preservation. For example, the larger relevant source area of surface lake sediment results in a higher abundance of Betula in pollen assemblage from surface lake sediment, whereas the tendency to disintegrate thin-walled pollen types in topsoil leads to a higher proportion of resistant pollen, such as Asteraceae. Linear regression analysis indicates that the Artemisia/Chenopodiaceae (A/C) ratio in pollen assemblages of surface lake sediments can be used to indicate humidity changes in the study area. However, the A/C ratio in topsoils should be used carefully. Our results suggest that pollen data from surface lake sediments would be better references for interpreting the fossil pollen assemblages of lake cores or lacustrine profiles.

A chrysophyte-based quantitative reconstruction of winter severity from varved lake sediments in NE Poland during the past millennium and its relationship to natural climate variability

Chrysophyte cysts are recognized as powerful proxies of cold-season temperatures. In this paper we use the relationship between chrysophyte assemblages and the number of days below 4 °C (DB4 °C) in the epilimnion of a lake in northern Poland to develop a transfer function and to reconstruct winter severity in Poland for the last millennium. DB4 °C is a climate variable related to the length of the winter. Multivariate ordination techniques were used to study the distribution of chrysophytes from sediment traps of 37 low-land lakes distributed along a variety of environmental and climatic gradients in northern Poland. Of all the environmental variables measured, stepwise variable selection and individual Redundancy analyses (RDA) identified DB4 °C as the most important variable for chrysophytes, explaining a portion of variance independent of variables related to water chemistry (conductivity, chlorides, K, sulfates), which were also important. A quantitative transfer function was created to estimate DB4 °C from sedimentary assemblages using partial least square regression (PLS). The two-component model (PLS-2) had a coefficient of determination of Rcross2 = 0.58, with root mean squared error of prediction (RMSEP, based on leave-one-out) of 3.41 days. The resulting transfer function was applied to an annually-varved sediment core from Lake Żabińskie, providing a new sub-decadal quantitative reconstruction of DB4 °C with high chronological accuracy for the period AD 1000–2010. During Medieval Times (AD 1180–1440) winters were generally shorter (warmer) except for a decade with very long and severe winters around AD 1260–1270 (following the AD 1258 volcanic eruption). The 16th and 17th centuries and the beginning of the 19th century experienced very long severe winters. Comparison with other European cold-season reconstructions and atmospheric indices for this region indicates that large parts of the winter variability (reconstructed DB4 °C) is due to the interplay between the oscillations of the zonal flow controlled by the North Atlantic Oscillation (NAO) and the influence of continental anticyclonic systems (Siberian High, East Atlantic/Western Russia pattern). Differences with other European records are attributed to geographic climatological differences between Poland and Western Europe (Low Countries, Alps). Striking correspondence between the combined volcanic and solar forcing and the DB4 °C reconstruction prior to the 20th century suggests that winter climate in Poland responds mostly to natural forced variability (volcanic and solar) and the influence of unforced variability is low.

Characterizing magnetic mineral assemblages of surface sediments from major Asian dust sources and implications for the Chinese loess magnetism

Eolian dust plays an important role in the Earth’s climate system. Environmental magnetism has been widely used to trace dust variations at different spatial and temporal scales. However, the magnetic properties of sediments from key dust sources have not been well determined. In this study, surface samples from potential dust sources in inner Eastern Asia were systematically investigated. Our results indicate that ferrimagnetic and antiferromagnetic minerals are both present in surface sediments and that they have broad grain size distributions. Ferrimagnetic components are dominated by partially oxidized coarse-grained (pseudo-single domain and multi-domain) lithogenic magnetite particles with minor contributions from pedogenic fine-grained (single domain and superparamagnetic) particles. Antiferromagnetic hematite can be classified into three groups in terms of diffuse reflectance spectroscopy (DRS) band positions (P 560 nm, P 545 nm, and P 535 nm, where numbers indicate the DRS band wavelength for hematite). The first group (P 560 nm) is the coarse-grained hematite of lithogenic origin and is mostly confined to western China. The P 535 nm group is of pedogenic origin. The P 545 nm group is an intermediate phase that is present both in surface samples from the source regions and in loess. Therefore, the P 545 nm and P 535 nm groups are related to eolian inputs to the Chinese Loess Plateau and pedogenic processes, respectively. In addition, significant differences exist between the magnetic properties of eolian material from sources and depositional regions due to gravitational sorting. These insights provide strong constraints on interpretation of dust signals recorded by the Chinese loess and marine sediments from the North Pacific Ocean.

Nannofossils in upper quaternary bottom sediments of back-arc basins in the southwestern Pacific

The analysis of calcareous nannoplankton assemblages in bottom sediments sampled during Cruise 21 of the R/V Akademik Mstislav Keldysh in three areas located in back-arc basins of the southwestern Pacific (western Woodlark in the Solomon Sea, Manus in the Bismarck Sea, Central Lau) reveal that they belong to the Emiliania huxleyi Acme Zone, the most detailed one in the Gartner’s scale of 1977. The content of coccoliths and their taxonomic composition indicate warm subtropical-tropical conditions. Long cores demonstrate a decrease in species diversity reflecting the transition from the cold late Pleistocene to the Holocene. The changes in species diversity and presence/absence of thermophilic representatives indicate transformation of depositional environments with unstable conditions in the water column and bottom layer, seismic activity, and widely developed processes of sediment redistribution and reworking.

Reply to comment on “Reassessing the sedimentary deposits and vertebrate assemblages from Ponte Galeria area (Rome, central Italy): An archive for the Middle Pleistocene faunas of Europe” by Sardella et al.

Reply to comment on “Reassessing the sedimentary deposits and vertebrate assemblages from Ponte Galeria area (Rome, central Italy): An archive for the Middle Pleistocene faunas of Europe” by Sardella et al.