Palaeoenvironmental Inferences Research Articles

Climate change versus land management in the Po Plain (Northern Italy) during the Bronze Age: New insights from the VP/VG sequence of the Terramara Santa Rosa di Poviglio

The sedimentary infilling of the moat surrounding the Villaggio Piccolo of the Terramara Santa Rosa di Poviglio was analysed in order to obtain palaeoenvironmental inferences from sediments and pollen assemblage. The high-resolution stratigraphic sequence preserves evidence of the environmental changes that occurred in the Po Plain, in Northern Italy, during the Late Holocene. Our interdisciplinary approach permitted to study climatic and anthropic contributions to the environmental changes in this region. The relationships between these changes and land-use changes were investigated focussing on adaptive strategies of the Terramare people during the Middle and Recent Bronze ages (1550–1170 yr BC). The Terramare are archaeological remains of banked and moated villages, located in the central alluvial plain of the Po river. The Terramara of Santa Rosa consists of two adjoining settlements (Villaggio Grande and Villaggio Piccolo); the moat that separates the two parts of the site is c. 23 m large and reaches a maximum depth of 4 m from the extant ground level. The stratigraphic sequence VP/VG exposed by archaeological excavation inside the moat was sampled for pedosedimentary, thin section, and pollen analyses. Chronology is based on archaeological evidence, stratigraphic correlations and radiocarbon dating. Pedosedimentary features and biological records (pollen of aquatics and algal remains) demonstrate that shallow water, probably subjected to seasonal water-level oscillations, has always been present in the moat. In the lower units of the sequence, the laminations indicate standing water, while occurrence of reworked pollen testified the supply of sediments to the plain from catchment zones located in the Apennine. Open vegetation was widespread; economy was based on wood management, fruit collection on the wild or from cultivated woody plants, crop fields with a fairly diversified set of cereals especially increasing in variety during dryness or phases of water crisis. Probably, grapevines were cultivated near the moat, where the wet habitat was favourable to the growing of wild plants. The extraordinary high-resolution of this sequence makes visible the management of woods (including coppicing) at the Middle Bronze and early Recent Bronze ages. The economy of Santa Rosa di Poviglio should have been probably less based on animal breeding than it was in the other Terramare villages already studied for pollen. This research also confirms the chronological correspondence between an environment stressed by dry conditions and the collapse of the Terramare civilization.

Radiocarbon Dating of Marine Shells from the Gulf of Cadiz: The marine radiocarbon reservoir effect, its variability during the Holocene and palaeoenvironmental inferences.

The ocean reservoir is deficient in radiocarbon compared with the atmosphere and, consequently, an offset in 14C age exists between coeval samples containing marine carbon versus those containing terrestrial carbon. A record of past reservoir ages is preserved in the 14C ages of contemporary marine and terrestrial material. The quantification of the marine radiocarbon reservoir effect (ΔR) is of crucial importance to the correct calibration of the 14C ages of marine samples. For the southern Atlantic Iberian coast, for the last 3000 yr, ΔR takes the following values +69±17 14C yr (Barlavento coast), -26±14 14C yr (Sotavento coast), and -108±31 14C yr (Andalusian coast), which are in accordance with the oceanographic conditions present in each area. Results also suggest that during the 5th millennium cal BP very different oceanographic conditions (high positive ΔR values) prevail in the Barlavento and in the Atlantic Andalusian coastal areas and, consequently, in all the northern Gulf of Cadiz region, perhaps due to the extension of the Azores Front eastward along the Azores Current penetrating into the Gulf of Cadiz.

Palaeoenvironmental inferences from late Quaternary sediments of the Al Jafr Basin, Jordan

Sedimentological, palaeontological and mineralogical analyses of sediments from the endorheic Al Jafr Basin were conducted to better understand the depositional and hydrological conditions on the southern Jordan Plateau in the late Quaternary. Surficially exposed carbonate-rich sediments in the western part of the basin contain ostracod (micro-crustacean) shells of Ilyocypris cf. bradyi, Candona neglecta, Heterocypris salina, Fabaeformiscandona fabaeformis, Pseudocandona sp. and Herpetocypris brevicaudata. The shells of these and other more rare species, and charophyte and mollusc remains indicate that the sediments were formed in a wetland setting of shallow freshwater to slightly oligohaline ponds, streams and swamps. The present more northern distribution of some of the recorded taxa implies that climate conditions were probably cooler during the wetland formation. Radiocarbon age data for biogenic carbonate from two locations suggest that the wetland setting existed during the second half of Marine Isotope Stage (MIS) 3 or possibly earlier. A significantly higher water table must have existed in the basin during wetland formation; and wetter climate conditions are inferred for the catchment or at least for its highest and most humid westernmost part. Deflation and local sediment accumulation by wind and occasional sheet-wash events apparently prevailed in the region since MIS 2. Our newly presented data and inferences do not support the reconstruction of a previously reported large and relatively deep Pleistocene lake in the Al Jafr Basin. However, more extensive studies are certainly required for a detailed assessment of the Quaternary hydrological conditions in southern Jordan.

Proteome degradation in ancient bone: Diagenesis and phylogenetic potential

The species composition of vertebrate remains found on archaeological and palaeontological sites has proved to be a valuable source of information for reconstructions of past animal husbandry practices as well as for recovering palaeobiological and palaeoecological information. Molecular analyses provide an objective alternative method of species identification to traditional morphological approaches, particularly useful with fragmentary material; the most well-known being the analysis of DNA. However, more recent proteomics techniques are proving to offer powerful new approaches for obtaining molecular species identification and molecular phylogenies from much deeper within the archaeological record. Collagen is the most abundant and stable protein that can survive for millions of years in biomineralised tissues, but it has been well established for several decades that many other, potentially more informative, non-collagenous proteins (NCPs) also survive long into the archaeological and even geological records. This study investigates the potential mechanisms for biomolecule survival in ancient bone, as well as the extent to which the NCPs that do survive over hundreds of thousands of years yield useful phylogenetic information. Some of these NCPs are shown to yield species-specific information making them ideal for palaeoenvironmental inferences.

Toward a standard stratigraphical classification practice for the Baltic Sea sediments: the CUAL approach

The Late Pleistocene and Holocene glacial and postglacial sediments of the Baltic Sea basin are conventionally classified into units according to the so‐called Baltic Sea stages: Baltic Ice Lake, Yoldia Sea, Ancylus Lake and Litorina Sea. The Baltic Sea stages have been identified in offshore sediment cores by fundamentally different criteria, precluding detailed comparisons of the sediment units amongst different sea areas and studies. Here, long sediment cores and reflection seismic and pinger sub‐bottom profiles were studied from an offshore area in the Gulf of Finland, northern Baltic Sea. The strata are divided on the basis of sedimentological criteria into three allostratigraphical formations with subordinate allostratigraphical members and lithostratigraphical formations, following the combined allostratigraphical and lithostratigraphical (CUAL) approach. Sedimentological features are recommended as the primary stratigraphical classification criteria because they do not require the palaeoenvironmental inferences of salinity and water level that are inherent in the conventional classification practice. The presented stratigraphical division is proposed as a flexible template for future stratigraphical work on the Baltic Sea basin, whereby lower‐rank allounits and lithounits can be included and removed locally, while the alloformations will remain at the highest hierarchical level and guarantee regional correlatability. The stratigraphical division is compatible with international guidelines, facilitating communication to the wider scientific community and comparison with other similar basins.

Comment on “Lightning as a geomorphic agent on mountain summits: Evidence from southern Africa” by Knight and Grab (2014)

Insights into the possible effect of lightning strikes on rock breakdown are presented by Knight and Grab (2014) from a summit area in the Lesotho highlands. Based on their findings, the authors challenge the association of angular debris with frost shattering and use this as a platform for directing critique against palaeo-geomorphic studies. While the lightning strike data are not questioned directly here, the palaeo-environmental context within which the paper is set, the portrayal of former findings and the assumptions regarding weathering mechanisms in Lesotho are commented on. Frost shattering is the centre of Knight and Grab's weathering critique but, contrary to that stated in their text, none of the cited authors invoke this process in Lesotho. Other weathering processes that are speculated upon are not specific to cold climates either and thus cannot be used in support of their argument. In terms of debris and block distribution, lightning will not account for the preferential location of relict blocks and debris below the summits on south-facing slopes, or for the extensive valley floor accumulations that are documented in Lesotho. Knight and Grab also falsely portray former studies by implying that palaeo-environmental inferences in the area are drawn from block origin or morphology alone when the climatic signatures were derived from integrated assessments. In a palaeo-context, the relative contribution of lightning to debris production under dryer and colder conditions, when convective thunderstorm activity in the highlands was likely reduced, is also questioned. The weathering context, as well as the critique that Knight and Grab direct at other studies on relict landforms, is thus shown as inappropriate.

Chemico-mineralogical attributes of clays from the late Cretaceous–early Palaeogene succession of the Um Sohryngkew river section of Meghalaya, India: Palaeoenvironmental inferences and the K/Pg boundary

A continuous shallow marine 10 m thick succession within the Langpar Formation in the Um Sohryngkew river section of Meghalaya, containing late Maastrichtian through early Danian planktonic foraminiferal zones – CF4, CF3, CF2, CF1, P0, Pα and P1a and the K/Pg boundary (between CF1 and P0) that makes unique of its kind. The section has been re-studied and sampled for clay mineralogy to understand the palaeoenvironmental conditions prevalent in the region and to assess the K/Pg transition. The relative abundances of the clay mineral phases permitted a threefold sub-division of the studied section with a illite, illite/ smectite dominated lower part, illite, kaolinite and abundance of montmorillonite dominated middle part and kaolinite–montmorillonite dominated upper part. Enriched HREEs in the lower part of the succession suggest variations in the pH of alteration solutions. Most of the samples show positive cerium (δCe) and europium (δEu) anomalies, the former reflecting oxidizing conditions at the time of clay formation. Illite dominated clays present a positive Eu anomaly, formed at relatively higher temperatures than the clays with less illite and without Eu anomalies, whereas clays occurring in the lower and upper parts exhibit a prominent negative Eu anomaly. Shifts in the redox condition found in this section are more or less similar to the foraminiferal changes and Au, Pt, Pd anomalies. Clay mineralogical attributes and REE patterns, comparable to those of the known K/Pg boundaries, appeared within the CF3 and CF2 zones in the Um Sohryngkew river section. The sample at the boundary between CF3 and CF2 is marked by a negative <delta>Ce anomaly, high La/Yb and TOC values, suggesting that sea level rise during the upper part of CF3 was caused by tectonism rather than warming. The similar characteristics of clay minerals and REE patterns, attributed to the initiation of tectonic events during the CF3 zone, indicate environmental changes that affected the shelf area and the provenance of these sediments.

Mineral Chemistry of Clays Associated with the Jhilmili Intertrappean Bed in the Eastern Deccan Volcanic Province: Palaeoenvironmental Inferences and KTB Transition

Abstract Jhilmili intertrappean bed (~13 m thick) attains its significance with the recent discovery of brackish water ostrocod and planktonic foraminifera fossils (Keller et al. 2009; Khosala et al. 2009). Present XRD data revealed abundance of montmorillonite &amp;gt; montmorillonite/chlorite mixed layer &amp;gt; palygorskite in five physically distinct litho-units namely: (a) lower chocolate brown siltstone with green patches, followed by (b) brick red clayey siltstone, (c) greenish grey clay, (d) yellowish brown clay and (e) uppermost olive grey to dark brown silt layers in the succession-represent higher weathering indices and annual precipitation, reflecting cyclic, but longer spells of weathering. Occurrence of M/C mixed layer with the smectite in Jhilmili area is suggestive of their derivation from the later, whilst montmorillonite to palygorskite transformation is ascribed to the drastic changes in the humid to arid climate, where former served as a source of Al and some of the Si and Mg ions for the later. Jhilmili and Anjar clays represent similar charge occupancies at different sites, but later contains relatively higher amount of palygorskite, formed in the arid environment. Majority of the trace elemental data plots for Jhilmili clays lie within the upper and lower limits of infra (Lametas)-/inter-trappeans clays. The continuous release of Cu throughout the succession (mainly in the palygorskite dominated clays) indicates oxidizing conditions. PAAS normalized REE data plots for these clays show progressive enrichment in the HREE contents in the lower part, but, upper part of the succession is marked by positive cerium anomaly, reflecting oxidizing conditions prevailed at the later stage of the succession. These conditions continued, but, were not conducive to HREE enrichment as evidenced by their depletion in the upper part of the succession. The Ce anomaly observed in the middle part of the succession is similar to that form by continental weathering of the basalt, ascribed to Ce precipitation in the oxic environment, thus suggestive of drastic changes in the oxidizing conditions. Thermodynamic data-sets for Jhilmili clays show I/S mixed layer and celadonite compositions, whereas, Jabalpur infra-/inter-trappean clays correspond to Mg smectites and celadonite end members, thus, representing compositional commonality with those of the other clays derived from the continental weathering of basalt protolith. Jhilmili smectites and smectite-chlorite mixtures show compositional similarity with the dioctahedral and trioctahedral smectites and the smectites formed at 250ºC, having compositions between trioctahedral smectite and chlorite, thus, assigning high temperatures for their formation, where the heat required for the formation of these clays was possibly derived from the hydrothermal fluids, associated with the Deccan volcanism.

Late Miocene continental birds from the Cerro Azul Formation in the Pampean region (central-southern Argentina)

Cenizo, M.M., Tambussi, C.P. & Montalvo, C.I., iFirst Article. Late Miocene continental birds from the Cerro Azul Formation in the Pampean region (central-southern Argentina). Alcheringa, 1–22. ISSN 0311-5518. The oldest known birds from the Cerro Azul Formation are described, including the oldest records for the genera Eudromia and Nothura (Tinamidae), Milvago (Falconidae), Pterocnemia (Rheidae) and an undetermined Tyrannidae. The first remains of Phorusrhacidae for this formation are reported and a specimen previously referred to the giant teratorn Argentavis magnificens is reassigned to this family. We outline and update the current knowledge of the groups studied herein. The palaeornithological record from the Cerro Azul Formation is congruent with palaeoenvironmental inferences previously drawn from mammalian assemblages recovered from this unit, which point to the existence of open environments, possibly xerophyllous shrubby steppes, perhaps with some trees. These records are the first indications of a typically Pampean bird fauna at the end of the late Miocene in central-southern Argentina.

An exceptionally rich hyaena coprolites concentration in the Late Miocene mammal fossil site of La Roma 2 (Teruel, Spain): Taphonomical and palaeoenvironmental inferences

The La Roma 2 (Alfambra, Teruel, Spain) Late Miocene vertebrate fossil site is characterised by a rich and unusual concentration of mammalian coprolites distributed along a band running in a NNE–SSW direction sub-parallel to a fossil bone assemblage. These coprolites contain residues that provide direct evidence regarding the diets of the organisms that produced them. They contain a variety of inclusions, such as small bone fragments, pollen grains and fungal spores. The bone fragments show evidence of heavy digestion, including corrosion and rounded and highly polished fracture surfaces. All the coprolites at the site are circular in section, some of them showing two convex ends, and others with both concave and convex (sometimes pointed) end. Their shape and size match the faeces produced by the extant spotted hyaena, Crocuta crocuta. X-ray diffraction analysis showed these coprolites to be mostly composed of calcium phosphate with small amounts of quartz and gypsum. All these characteristics suggest that they represent the excreted remains of digested bones; their size and morphology allow their attribution to the Late Miocene hyaenid Lycyaena chaeretis. The spatial distribution of the coprolites and the lack of tooth marks on the surface of the nearby fossil bones suggest that these elements were transported to their present positions from different places of origin by different water currents. The palynological analysis of the coprolites suggests their makers lived in an open environment with relatively scarce vegetation and under relatively cool climatic conditions but where water was available. Pines were the dominant tree taxa, but oak, hazel and birch were also present.

Effect of simulated faunal impoverishment and mixture on the ecological structure of modern mammal faunas: Implications for the reconstruction of Mio-Pliocene African palaeoenvironments

The strong link between environment and the ecological diversity of communities is often used for drawing palaeoenvironmental inferences from fossil assemblages. Here we focus on the reliability of fossil samples in comparison to original communities when inferring palaeoenvironments from the ecological diversity of fossil mammal faunas. Taphonomic processes and sampling techniques generally introduce two kinds of biases in fossil samples: 1) the directional impoverishment of communities, i.e. the absence of some specific categories of bones, individuals or species; and 2) the mixture of several communities, temporally (time-averaging) and/or spatially (space-averaging). We explore the impact of such alterations on ecological diversity and taxonomic richness by simulating an impoverishment in small species (1–45 kg) and a mixture of communities on an original dataset of 50 modern African communities. The progressive impoverishment in small species in a mammal community induces a relative enrichment in terrestrial and grazing species and a depletion (or even the disappearance) of several ecological categories (e.g., fossorial, arboreal, sub-arboreal, frugivorous, omnivorous and insectivorous species), thus leading to the ecological homogenisation of the altered communities. Other categories (carnivorous species, browsers, mixed feeders and sub-aquatic species) prove stable and seem to be good estimates for the relative abundances in the parent communities. Ideally, palaeoenvironmental inferences should be drawn from those ecological categories. For strong degrees of impoverishment, the discriminating power of the ecological diversity is reduced and other proxies should be used. Once the degree of impoverishment is assessed, it becomes possible to consider the condensation of several communities into a single fossil sample by comparing its taxonomic richness with those of modern communities, first impoverished to the same level. The mixture of communities tends to increase the taxonomic richness but does not significantly modify the overall ecological diversity. As a case study, we applied this approach to 15 African mammal samples from the late Miocene–earliest Pliocene, a period of particular interest, as it saw the emergence of hominins, together with faunal turnovers, and major climatic and environmental changes. Most of our fossil samples, especially those that yielded early hominins, appear altered to different degrees by taphonomic processes and sampling techniques, meaning that their faunal structures may not be comparable and that their inferred palaeoenvironmental differences may not be genuine.

Midges as quantitative temperature indicator species: Lessons for palaeoecology

Calibration data sets give a unique opportunity to establish patterns of biological existence and their statistical associations with environmental variables. By use of calibration data sets, environmental variables can be inferred quantitatively. The resulting long time-series may assist in distinguishing natural environmental variability from human-induced variability, both in terms of climate change and biotic turnover. However, the validity of the palaeoenvironmental reconstructions depends on their accuracy, precision and sensibility. Before performing palaeoenvironmental inferences, key mechanisms controlling contemporary species’ distribution, abundances and dynamics should be identified and understood. An inference model is developed to produce reconstructions. A major challenge lies in validating and interpreting the reconstructions. Calibration data sets involving midges (Diptera: Chironomidae) suggest that climate has a broad-scale, regional control over midge existence and abundance, often over-riding the influence of local within-lake variables. In recent years, the use of midges as quantitative indicators of past temperatures has greatly expanded. As the number of reconstructions increase, especially in Fennoscandia and North America, it seems the among-site variability is so large that it is unlikely to be due only to local differences in climate. Hence, we question whether the long climate gradients in calibration data sets can accurately be used to calibrate local variables, when most local gradients in time and space are short. Ten Holocene chironomid-inferred temperature curves from Fennoscandia are compared. We illustrate some general principles in palaeoecology by identifying factors that may cause bias. Especially, we consider how calibration data sets simplify the complexity of the real world by maximizing single ecological gradients and by not taking into account co-varying variables. We give some recommendations and criteria that chironomid analysis should meet in order to improve the reliability of the temperature inferences. Finally, we discuss how the complex interactions between species and environment may have implications when we aim at predicting future biodiversity.

Rock weathering on the eastern mountains of southern Africa: Review and insights from case studies

The mountains in the eastern region of southern Africa are of significant regional importance, providing for a diverse range of land use including conservation, tourism and subsistence agriculture. The higher regions are comprised of flood basalts and are immediately underlain by predominantly aeolian-origin sandstones. Our understanding of the weathering of these basalts and sandstones is reviewed here, with particular focus on the insights gained from the Lesotho Highlands Water Project and an ongoing study into the deterioration of rock art. While the chemical weathering attributes of the basalts have been substantially investigated, it is evident that the environmental surface conditions of rock moisture and temperature, as affecting weathering processes, remain largely unknown. Within the sandstones, studies pertaining to rock art deterioration present insights into the potential surface weathering processes and highlight the need for detailed field monitoring. Outside of these site-specific studies, however, little is understood of how weathering impacts on landscape development; notably absent, are detail on weathering rates, and potential effects of biological weathering. Some palaeoenvironmental inferences have also been made from weathering products, both within the basalts and the sandstones, but aspects of these remain controversial and further detailed research can still be undertaken.

An ice cap landsystem for palaeoglaciological reconstructions: characterizing the Younger Dryas in western Scotland

This paper reviews the contrasting behaviours of ice caps and icefields, defines a generic landsystem model that can effectively discriminate between them, and applies the model to landform-sediment assemblages in an area of western Scotland. Such a model is necessary, since many palaeoenvironmental inferences from formerly glaciated terrains are based on the geometry, extent and dynamics of reconstructed ice masses. The validity of these glacier reconstructions is dependent on the accurate initial interpretation of relict landforms and sediments, and their inter-relationships. A new landsystems model is presented here, in which individual geological and geomorphological elements are checked against a set of eight theoretical diagnostic criteria that characterize the style of former glaciation. When applied to a 1200 km 2 area of the western Scottish Highlands, the landsystem tool predicts (1) an extensive Younger Dryas ice cap with a maximum surface elevation of 900 m above sea level, implying colder or wetter conditions than previously thought, and (2) the survival of an independent mountain icefield in part of the area during deglaciation. Glaciological theory, proxy palaeoenvironmental data and established glacier-climate-topography relationships support these predictions, thereby giving credibility to the landsystem methodology as a generic tool for palaeoglaciological reconstructions.

Fossils, sediments, tectonics

Tectonic displacement and small-scale tsunamis apparently affected deposition of the Kolymbia limestone, Cape Vagia, Rhodes, Eastern Mediterranean. Coarse beds interrupt the sequential build-up of this Pliocene–Pleistocene bryomol limestone. Celleporid bryozoans, bivalves, and brachiopods dominate these beds. The palaeoecology of the thicket-forming Celleporaria palmata is re-evaluated and subsequently revised. The limestone comprises two parasequences in a transgressive systems tract, and deposition occurred at palaeodepths between 30 and 120 m. At intervals, tectonic movements lowered relative sea level and sent slumps of shallow-water fauna downslope. The depositional history was validated using independent sets of data: sediment structure and grain size, palaeobathymetry using bryozoan growth forms and occurrences of modern representatives of bryozoans and other taxa, basin configuration, and regional tectonics. Concordance of these lines of evidence provides a means of evaluating confidence in palaeoenvironmental inferences.

Plio-Pleistocene climatic change in the Turkana Basin (East Africa): Evidence from large mammal faunas

We investigated palaeoclimatic change in the Turkana Basin during the Pliocene climatic shift toward increased aridity in Africa. We analyzed the palaeoecology of this area using mammal faunas as environmental indicators. Twenty Plio-Pleistocene fossil assemblages and a comparative dataset of 16 modern localities covering a wide range of climatic and ecological conditions across Africa were analyzed. We constructed community profiles using taxonomic variables which reflect ecological information. Principal component analysis and bivariate correlation were used to study changes in the community structure of these mammalian faunas and to draw palaeoenvironmental inferences. Subsequently, least-squares regressions yielded climatic estimates (annual rainfall and drought length) for the studied period. An additional set of 8 modern faunas was used to validate these regression models. The climatic estimates showed a drying trend throughout the sequence. The biomes in the Turkana Basin changed from semi-evergreen rain forest to deciduous woodland and savanna during the middle-late Pliocene. This was the most important climatic shift detected in our study. Evidence suggests a continuous presence of savannas from 2.5 million years ago onwards. This pattern of climatic change is consistent with isotopic evidence on global climate, and with independently derived regional palaeoenvironmental evidence (i.e., micromammals, palaeovegetation, soil carbonates and palaeosols).

Cretaceous (Wealden) climates: a modelling perspective

This paper describes the results from a new palaeoclimate modelling exercise for the Early Cretaceous (Barremian) focussed on the Weald (SE England), using a Limited Area Numerical Climate Model (LAM). The palaeoclimate model uses appropriate Barremian boundary conditions and simulates a climate with seasonal surface temperatures akin to those occurring in parts of the modern southern Mediterranean. Cold month mean temperatures are simulated as 4–8 °C, whilst warm month mean temperatures may reach 36–40 °C. Precipitation rates are high during all seasons with little evidence for prolonged drought. The average precipitation rate simulated for any one month is 4–8 mm/day, whilst during parts of the winter (December, January and February) precipitation rates may exceed 16 mm/day. No present-day analogue is available for the climatological pattern predicted for the Barremian. This result differs from other palaeoclimate interpretations for the Weald based on proxy climate data. These data have been interpreted as showing the existence of a seasonal precipitation pattern with a pronounced dry season. The data/model inconsistency can be resolved by careful examination of the model-predicted moisture budget as a whole. We argue that many of the palaeoclimate moisture proxies record the net hydrological cycle (i.e., precipitation minus evaporation). Although the climate model simulates precipitation year round, the surface temperatures result in very high evaporation rates. Therefore, moisture availability during the Barremian in the soil and for plants during the summer months (June, July and August) is severely restricted even though precipitation levels are substantial. These results demonstrate the importance of considering the moisture balance as a whole rather than focussing on only precipitation when drawing palaeoenvironmental inferences from proxy data. The work underlines the benefits of using numerical climate models in conjunction with proxy data in understanding past climates and environments.

Taxonomic fidelity of silicified filamentous microbes from hot-spring systems in the Taupo Volcanic Zone, North Island, New Zealand

ABSTRACTModern, silica-precipitating hot springs, like those found in the Taupo Volcanic Zone (TVZ) on the North Island of New Zealand, are natural laboratories for assessing microbial silicification. Many of the silicified microbes found in the siliceous sinters of these spring systems seem to be life-like replicas of the original microbes. Such preservation reflects the fact that many of the microbes are replaced and encrusted by opal-A before they are destroyed by desiccation and decay. The taxonomic fidelity of these silicified microbes depends on the preservation potential of those features which are needed to identify them. For example, identification of extant cyanobacteria, relies on as many as 37 different features, most of which are not preserved by silicification.In the hot-spring systems of the TVZ, characterisation of cyanobacteria which have been replaced and encrusted by opal-A is typically restricted to colony morphology, the length, diameter and morphology of the filament, and the presence/absence of septa, branching or a sheath. In many cases, description is limited to a subset of these parameters. Such a limited set of morphological characteristics severely impedes identifications in terms of extant taxa. The physical changes which accompany the stepwise diagenetic progression from opal-A to opal-CT ± opal-C to microcrystalline quartz may lead to further degradation of the silicified microbes and the loss of more taxonomically important features. Clearly, considerable care must be taken when trying to name silicified microorganisms and make palaeoenvironmental inferences.

Non-marine biota from the Lower Permian of the central Southern Alps (Orobic and Collio basins, N Italy): a key to the paleoenvironment

The Lower Permian in the central Southern Alps yields an important low-diversity fossil assemblage which was deposited in a varied continental setting, showing mainly alluvial fan to lacustrine and, locally, playa-like floodplain environments. The present study is not taxonomical and its objective is to make a first report of new invertebrate organisms and trackways discovered in the Orobic and Collio basins. Such a fossil record, which comprises freshwater jellyfishes, arthropod tracks, stromatolites, algae and other organisms, will further our knowledge about the local and regional geological history of the central-western Southern Alps and improve our understanding of Early Permian palaeoenvironments. On the whole, in both intramontane basins the ichnodiversity and fossil content decreases from a stratigraphic lower portion, mainly lacustrine and alluvial, towards an upper one, characterised by coarse alluvial deposits to floodplain fines. On the basis of both the already known palaeontological data from the two basins, mainly macroflora and tetrapod footprint associations, and the recently discovered taxa, we tried to make reliable palaeoenvironmental inferences and, possibly, hypothesise on a climatic change, which could have occurred during the Early Permian.

INTERPRETAÇÃO DO TESTEMUNHO T-101, (32°05'S; 47°35'W) COM BASE EM NANOFÓSSEIS CALCÁRIOS - CONE DO RIO GRANDE, RIO GRANDE DO SUL, BRASIL

The present paper refers to the study of the calcareous nannofossils of the piston core T-101, placed in the Rio Grande do Sul Continental Elevation, latitude 32°05'S and longitude 47°35'W. The piston core presents 670cm of length and was obtained in a depth of 3.200m in the Rio Grande Cone area, during the accomplishment of the oceanography campaign GEOMAR VII, 1976. The analysis of these microfossils shows that they do not have a sequential distribution along the piston core, occurring concentrated at 670cm, 620cm and 580cm of the base and at 15cm of the top. Through the taxonomic identification of these microfossils, reworked material was detected in the base of the piston core mixing the early Pleistocene species with the Pliocene species. In the top, exist an assemblage of late Pleistocene. In the interval 580-15cm, calcareous nannofossils doesn't exist. Palaeoecologic and palaeoenvironmental inferences were presented. As the same time, took place the correlation of the top of the Zone Calcidiscus macintyrei of Gartner, 1977 of lower Pleistocene with the medium part of the magnetostratigraphic Matuyama unit and of the Zone Emiliania huxleyi of Gartner, 1977 with the superior part of the Brunhes unit.