Search

The Miocene palaeogeography of the western Amazonian Foreland Basin (Venezuela, Colombia, Ecuador, Peru and western Brazil) and the Parana Basin (mainly Argentina) are contentious. Several studies have hypothesized for and against a possible connection of these epicontinental depositional systems during Miocene. However, the lack of well defined palaeoenvironmental data, especially from the Bolivian lowlands, has hindered the delineation of the Miocene palaeogeography in these areas. The objective of this study is to provide new data concerning this problem. This paper presents sedimentological and ichnological data from the Quendeque Formation in the northern Subandean zone of Bolivia (lat. 15°S). This virtually unstudied formation relates the marine-influenced Paranan (northernmost reported occurrence lat. 18°S) and western Amazonian (southernmost reported occurrence lat. 13°S) depositional systems and is contemporaneous with them. The palaeogeographical significance of the new data and recently discovered tidal deposits from southern Peru (Madre de Dios) and western Brazil (Acre) is discussed. New palaeocurrent and rhythmite data from the Madre de Dios and Acre Sub-basins are presented. The studied deposits are interpreted as alluvial, deltaic and estuarine coastal plain. These data coupled with recently published data from south and central Bolivia indicate that thin Miocene tidally/marine influenced levels are present throughout the Bolivian forelands. The distal–proximal facies relations between the Late Miocene Chaco and Madre de Dios strata, and the south–southwest oriented palaeocurrent directions collected from the Madre de Dios Sub-basin suggest at least South Atlantic source for the marine influence in these areas. The episodically open hydrodynamic connection between the southwestern Amazonia and Paranan Sea may have provided a dispersal route, especially for fresh-water and euryhaline aquatic taxa. Thus, the results may explain the reported fossil faunal similarities between these areas and the modern biogeography of certain aquatic species.

This paper deals with Holocene coastal changes of the Astakos plain in Akarnania, NW Greece. Palaeoenvironmental scenarios are based on the analysis of the lateral and vertical distribution patterns of sedimentary facies. Sediments from vibracorings were studied using geomorphological, sedimentological, microfaunal, palaeobotanical and geochemical methods. A geochronostratigraphy was achieved by 14C-AMS-dating of organic matter. We present palaeogeographical maps for different points in time since the mid-Holocene. The evolution of the coastal area was generally controlled by the migration of a complex system of a shallow marine embayment, an adjacent lagoonal environment and an adjoining coastal lake forced by the interaction of sea level rise, tectonic movements, and sediment supply from the hinterland. The maximum transgression of the Ionian Sea took place at circa 5500 cal BC reaching approx. 1.1 km inland. The lagoon as well as the coastal lake had their largest dimensions around 4500 cal BC indicating a more humid climatic period. In the course of a long-lasting regression, an asymmetric sedimentation pattern developed. Around 2500 cal BC it was characterized by strong fluvial deposition of the Xeropotamos in the western plain and a small and narrow marine embayment with associated lagoonal to limnic coastal water bodies in the eastern plain. The latter were related to karstic springs draining the adjacent Rigani ridge. Around 500 cal BC the coastline lay about 200 m landward of its present position. Possible harbour sites for the ancient polis of Astakos are (a) the area of modern Astakos where a mole in a position seawards of the present coast would have guaranteed deep water conditions for anchoring, or (b) the southeastern fringe of the plain where deep water prevailed and the nearby freshwater outlet protected the site from rapid siltation. We found increased torrential activity (i) for the 6th–5th millennium BC, (ii) for the 2nd half of the 1st millennium BC until Roman times, and (iii) at the end of the 19th century AD. At least the two younger phases are mostly due to anthropogenic soil erosion. Between the 4th and the 2nd millennium BC a period of ecological stability existed. Relative changes in sea level for the Bay of Astakos were reconstructed for the first time. Since the mid-Holocene, the relative sea level has never reached a higher position than today. It rose from 12.50 m b.s.l. at 6200 cal BC via 2.20 m b.s.l. at 500 cal BC to its present level. Besides eustatic reasons, tectonic subsidence due to the half graben structure of the area is the main trigger of the relative rise in sea level.

In this paper, a survey on the Messinian section of Can Vilella, in the intramontane basin of La Cerdanya (Pyrenees) is presented. The mammalian association, composed of insectivores, rodents and lagomorphs, is a very atypical one compared to other late Turolian (Messinian) assemblages from Spain and Western Europe, including Central European taxa such as Epimeriones aff. austriacus, which are very rare or absent in the late Miocene from Spain and, even, from Western Europe. The palynological record indicates a riparian forest with abundance of marshy herbs. A magnetostratigraphic study reveals a reverse polarity span for most of the section, whereas in the upper part normal polarities are found. According to the magnetobiostratigraphic correlation established in other basins, the normal geomagnetic episode at the top of the section should correspond either to chron C3An.2n or C3An.1n. In any case, the Can Vilella association clearly predates the onset of the Messinian Salinity Crisis (MSC) in the Mediterranean. This means that the set of climatic and palaeogeographic events associated with the MSC cannot account for the anomalous association from Can Vilella. A discussion as to whether an altitudinal component could be responsible for such an anomaly is undertaken.

This paper explores some of the new perspectives resulting from re-examination of the pollen data from my 1978 comprehensive analysis of 100 coprolites from one of the earliest identified prehistoric latrines in North America. Of particular interest are the empirical results of previously unavailable pollen concentration calculations for some of the prehistoric specimens as well as a time-series of 82 modern fecal specimens produced during an experiment yielding data on the rate of elimination of specific pollen grains from the human system. Experimental data of all sorts are needed to extend coprolite analyses and interpretations, particularly from pollen-ingestion studies conducted with more volunteers over long periods of time. Parasitological studies of human coprolites will benefit from experimental data to determine the fate of the constituents of human feces ingested by dogs. The application of specialized techniques at the microscope, such as Intensive Systematic Microscopy ([Dean, G., 1998. Finding a needle in a palynological haystack. In: Bryant, V.M., Wrenn, J.H. (Eds.), New Developments in Palynomorph Sampling, Extraction, and Analysis. Am. Assoc. of Stratigraphic Palynologists Foundation., Contribs Series No. 33, pp. 53–59]), to locate and quantify rare pollen types needs to be explored. Easy and useful ways to express the abundance of macroremains in a coprolite are also needed.

A loess–paleosol sequence and a lake sediment record from the central Hexi Corridor in the drylands of NW China show patterns of persistent millennial- to centennial-scale climate variability during the Holocene epoch, which can be well correlated with abrupt climatic events reported from the North Atlantic and the Asian monsoon-dominated regimes. Our results show that the drylands in NW China might have been regulated both by the westerlies and by the East Asian summer monsoon (EASM) in a roughly synchronous manner. It seems that cold–dry intervals in the central Hexi Corridor may generally correspond to cooling phases in high latitudes of the Northern Hemisphere, and that cold/warm–wet intervals largely correlate with relatively warm phases in northern high latitudes. A candidate mechanism involving NAO/AO and ENSO dynamics is tentatively proposed to account for this synchroneity. Climatic patterns may be spatially different in the NW China drylands in response to the changing predominant control of either the westerlies or the EASM, depending on the contrast of their relative strengths. Glacier meltwater discharges associated with alpine warming may be partly responsible, at least for the two records discussed in this paper, for such spatial heterogeneity of climatic changes during the Holocene. More work is needed to evaluate the individual roles and combined impacts of the EASM, the westerlies and alpine glacier meltwater regulation on the NW China dryland dynamics.

This paper reports and discusses the distribution, petrography and mineral chemistry of granule- to boulder-size clasts in the Early Pliocene to Quaternary sedimentary succession recovered by the CIROS-2 drill hole, located near the mouth of the Ferrar Glacier (McMurdo Sound). In the Pliocene interval (166.47–99.27 mbsf), Early Paleozoic basement granitoids (monzogranites and granodiorites) are most common, apart from the basal 13-m-thick diamictite unit, which is dominated by basalt clasts from the late Cenozoic McMurdo Volcanics. In the Pleistocene interval (99.27–0 mbsf) basement granitoids are also the most common, but are largely tonalities. Gabbros and dolerites of the Jurassic Ferrar Supergroup are a minor persistent component throughout the core. In contrast, basement metamorphic rocks and Beacon Supergroup sandstones are present only within the lowest part of the core, the former disappearing above ca. 70.20 mbsf, and the latter above ca. 99.30 mbsf. During Pliocene time, the clast assemblage is consistent with the main source of the detritus from basement rocks to the west, transported by an ancestral Ferrar Glacier through the Transantarctic Mountains, the basal basalts suggesting an invasion of Ross Sea ice into Ferrar Fjord from the south (in the area of Mount Discovery and Mount Morning volcanoes). The dominance of tonalite in Pleistocene clasts also suggests derivation from the coastal Blue Glacier area immediately to the south. The decrease in volcanic clasts from Late Pliocene time may relate to the final construction of the Mount Morning–Mount Discovery peninsula, which acted as a barrier to the northern movement of a grounded Ross Ice Shelf, whereas the appearance of the tonalite clasts suggests periods of ice flow from its present day provenance, the Blue Glacier–Miers Valley area, northward along the coast and then into Ferrar Fjord from the east.

The existence of a very large Lake Chad during the late Quaternary, Megalake Chad, has long been questioned. A Megalake Chad would present strong evidence for climatic fluctuations of great magnitude during the Holocene in tropical Africa. In this paper we used satellite data from Landsat and Modis sensors to collect and analyse new information on landforms in a 2 000 000 km2 region of the Lake Chad Basin. We detected 2300 km of remains marking the ancient shoreline of Megalake Chad. The satellite data also indicated many Saharan rivers and relict deltas leading to the long paleoshoreline. Large dunefield flattenings were observed and interpreted as the result of wave-cut erosion by the paleolake. Similarities were noticed between the landforms observed along the paleoshoreline of Megalake Chad and that of the former Aral Sea. This finding has significant consequences for reconstructing paleohydrology and paleoenvironments through the Lake Chad basin, and continental climate change.

This paper describes a multi-core lake sediment study using pollen, diatoms, and chironomids, together with magnetics and sediment biogeochemistry, as biotic and abiotic proxies to infer lake development in response to environmental change during the Holocene at Lochnagar in the eastern Highlands of Scotland. Diatoms are used to infer pH, chironomids to infer temperature, with pollen and plant megafossils acting as an independent proxy to validate these records and to provide insights into changes in catchment vegetation and soils. Lipid biomarkers are explored for their potential to provide additional information on lake productivity. The results indicate highly distinctive fluctuations in the loss-on-ignition (LOI) record, which are in phase with changes in some biotic (chironomid head-capsule concentration) and abiotic (coarse silt particle size fraction, and lipid and chlorine fractions) variables. Catchment-driven changes due to the development and degredation of soils, and the natural succession and human intervention on terrestrial catchment vegetation have the strongest influence on the diatom and chironomid assemblages. These catchment processes resulted in the natural acidification of the lake water. Post-industrial acidification of the lake was also influential on the lake biota. Climate-driven temperature change appears to have had only a weak influence on the biota with declines in cold stenothermic chironomid taxa in response to Early Holocene warming and declines in thermophilic chironomids in response to cooling at about 2600 cal. yr BP.

Many climatic proxy materials, such as ice cores, coastal and lacustrine sediments, and abandoned penguin rookeries, have been used to study palaeoclimatic changes and the palaeoenvironmental evolution of Antarctica. In this paper, we report another geological record-well preserved sedimentary sequences in the palaeo-notches in marine terraces of Fildes Peninsula, King George Island. Based upon grain size distribution and microtexture, geochemical element compositions, and radiocarbon dating, we identified the sediments in one palaeo-notch as lacustrine sediments, most likely deposited in a small palaeo-lake. From these data, we inferred that between 4000 and 3000 yr B.P. a moderate chemical weathering occurred and the climate was warmer and more humid than present, in good agreement with the findings from other climatic proxy materials. We believe that the sediments in palaeo-notches provide another reliable proxy material for studying the palaeoclimate and the palaeoenvironment in Antarctica.

Mesozoic polar forests represent an extinct biome subject to a polar light regime and elevated atmospheric CO2 levels. In this paper, new Cretaceous fossil plant assemblages are reported from NW Ellesmere Island, Canada at a paleolatitude of 75°N. These occur in a Campanian–Maastrichtian-aged interval of the Hansen Point Volcanics, a unit interpreted as a coastal plain/peat mire complex within an active volcanic setting. Studies of palynomorphs, sterile and fertile foliage, and wood indicate that mire environments were dominated by amber-producing taxodiaceous conifers with other conifers, ginkgos, cycads, angiosperms, ferns, lycopsids, and bryophytes occurring in subordinate numbers. Leaf physiognomic studies imply that most vegetation was deciduous. Occurrence of traumatic rings in the woods, together with a high year-to-year variability in ring width, indicates disturbed growing conditions possibly linked to a combination of frosts, volcanic eruptions, and flooding. Abundant charcoal remains indicate that an additional important disturbance process was wildfire. Results of this study compare closely with those from coeval circum-Arctic fossil sites, and augment our knowledge of the community-scale ecology of the Cretaceous polar biome.

Quaternary vertebrate extinctions attract wide interest because of the role ascribed to humans as agents of extinction, through either over-hunting or altering habitat. This paper examines faunal and floral records from the archaeological site at Tunnel Cave, Leeuwin–Naturaliste Region, southwestern Australia, which are relevant to the Mid-Holocene local extinction of Black-flanked Rock-wallaby (Petrogale lateralis). Possible factors causing the population decline include inter-species competition, over-hunting by humans or other predators, or vegetation habitat change caused by climate change or changes in human firing practices. Identification of macroscopic charcoal excavated at Tunnel Cave shows that changes in canopy trees began from 10,000 BP, consistent with post-glacial rainfall increases, and probably causing the encroachment of closed habitats and loss of grazing areas. These changes are consistent with other faunal shifts at Tunnel Cave and with faunal and identified charcoal records from the nearby Devil's Lair deposit. There is little evidence for changes in competitor or predator behaviour, although increasing geographic isolation of Petrogale habitats possibly exacerbated predator impacts. The timing of human occupations at Tunnel Cave in relation to vegetation change suggests that human firing was a minor influence on forest composition or structure. Petrogale's Mid-Holocene disappearance from the region is therefore attributable to climatically driven encroachment of closed habitat.

This paper outlines a general approach for analyzing siliceous microfossils from plants (phytoliths) in geologic sediments and uses this method to reconstruct the evolution of grasslands in the central Great Plains during the late Tertiary. Phytolith assemblage analysis is widely employed for reconstructing vegetation types in Pleistocene–Holocene paleoecology and archaeology, but no standardized methodology is currently available. Published phytolith studies are often system-specific and tailored after specific modern analogues. As a result, they vary in extraction technique, classification scheme, and method of inference. For ancient phytolith assemblages whose modern analogues are not well understood, a more general analytic approach is necessary. This analytic approach includes studying all size fractions (2–250 mm), using a classification scheme based on the available literature and a comprehensive modern phytolith reference collection, and comparing relative frequencies through time of all diagnostic phytoliths to interpret changes in habitat structure. This general method was applied to late Eocene to early Miocene sediment samples from northwestern Nebraska to deduce vegetation history and the results were compared to those obtained using a more specific technique [Stromberg, Paleogeogr. Paleoclimatol. Paleoecol. 177 (2002) 59]. In both studies, phytoliths were extracted by means of heavy liquid separation from the following lithostratigraphic units: (1) the late Eocene Chadron Formation and the early Oligocene Brule Formation (White River Group); (2) the late Oligocene–early Miocene Monroe Creek Formation, the early Miocene Harrison Formation and Anderson Ranch Formation (Arikaree Group); and (3) the early Miocene Runningwater Formation and Box Butte Formation (Ogallala Group). The two techniques, general vs. specific, produced results that differ markedly. Data from the general approach indicate the presence of relatively closed habitats in late Eocene to early Oligocene, typified by the presence of phytoliths from bambusoid grasses, woody and herbaceous dicotyledons, and palms. The introduction and spread of modern, open-habitat grasses, such as pooids, arundinoids, and panicoids, occurred between the late Oligocene and early Miocene. This resulted in a savanna or woodland type habitat by the early Miocene. In contrast, analysis using the specific method suggested the presence of open habitats in northwestern Nebraska from the late Eocene onward. The difference in interpretation based on the two approaches is principally due to inclusion of phytoliths >50 mm and the use of an expanded reference collection in the current study (general analytic approach). These results point to the importance of methodological choices in phytolith analysis and emphasize the usefulness of phytoliths as paleoecological indicators in the fossil record.

Stone tools discovered within uplifted marine terraces along the Red Sea coast of Eritrea at the Abdur Archaeological Site, dated to 125±7 ka (the last interglacial, marine isotope stage 5e), show that early humans occupied coastal areas by this time [Walter et al. (2000) Nature 405, 65–69]. In the present paper the stratigraphy, facies types and faunal composition from 25 measured sections of the tool-bearing Abdur Reef Limestone (ARL) are documented in detail and interpreted to provide a palaeoenvironmental context for the stone artefacts and a model for the deposition of the ARL. The ARL represents a complex marine terrace sequence. Erosional surfaces indicative of interrupted sedimentation are locally observed at two levels within the ARL. They subdivide the complex into three subunits, named 5e1, 5e2, and 5e3, representing different stages of the marine isotope stage 5e sea level highstand, comprising six depositional phases (I–VI) of the ARL. Subunit 5e1 begins with the initial transgression of the 5e sea level highstand leading to the deposition of widespread lag gravels on which rich oyster beds developed in shallow water (phase I). It further records rapid deepening accompanied by the deposition of low-energy carbonates with scarce corals (phase II), and later shoaling characterised by local development of a fringing reef tract in a sedimented environment (phase III). Subunit 5e1 is capped locally by a burrowed hardground that is laterally equivalent to depositional discontinuities, interpreted as caused by a globally recognised mid-5e sea level low stand (phase IV). Extensive reef build-up in response to sea level rise and improved conditions for coral growth characterises subunit 5e2 (phase V). A possible second sea level drop during the 5e highstand is inferred from the oyster-encrusted upper surface of subunit 5e2. Subunit 5e3 encompasses restricted coral patches that developed on the upper surface of the underlying subunit during the last stage of the 5e marine high stand (phase VI). Two different toolkits are found in the ARL. One consists of bifacial hand axes and cores of the Acheulian industry, typically associated with the oyster beds encrusted on the transgressive lag deposits. The other consists of Middle Stone Age (MSA)-type obsidian flakes and blades, mainly found in the nearshore and beach environments alongside debris from marine invertebrates and large land mammals. The distribution of these tools suggests that foraging activities of early humans varied with environmental setting. The Abdur Archaeological Site represents a late example of the Acheulian/MSA transition, seen as a benchmark for early modern human behaviour, and is, to date, the earliest well-dated example of early human adaptation to marine food resources.

Understanding the evolution of the surface circulation and the patterns of upwelling in the Atlantic is important not only because of the ocean’s crucial role in the present-day thermohaline circulation, in supplying heat to high latitudes, but also because of the significant petroleum reservoirs found around the basin. In this paper we examine the upper ocean circulation during four time-slices – the Kimmeridgian (c. 155 Ma), the Cenomanian (c. 100 Ma), the Maastrichtian (c. 70 Ma) and the Early Eocene (c. 50 Ma) – using a 1.5-layer, reduced-gravity, ocean model. For each time-slice the upwelling fields predicted from simulations of wind-driven upper layer circulation are compared with the deep-sea and continental margin sedimentary records. The boundary configurations at each time-slice are the subject of sensitivity tests, where matching of both deep-sea and coastal sedimentary records with the model-predicted upwelling fields is used to suggest best fits between model and geological data. Our model runs are consistent with there being a deep-water connection to the Pacific at each time period after the Kimmeridgian, with such a link being most important to the geological–ocean-model match in the Maastrichtian. No period after the Kimmeridgian produced a stable ocean simulation with a deep-water connection to Tethys. Our simulations c. 100 Ma suggest that a deep-water connection between the North and South Atlanctic was not established until after the Cenomanian. All time-slices show a clear western boundary current in the North Atlantic, although generally only a third to half the strength of today’s. A similar difference is found between tropical palaeo-productivity at each run, and today’s more productive Atlantic Ocean. We conclude that upwelling and anoxia are not necessarily independent means of producing organic-rich marine sediments. Most such sedimentary deposits laid down during the four time-slices can be linked to the presence of upwelling zones. Thus, where anoxia is well-established we suggest that upwelling may help supply organic material to the de-oxygenated bottom waters.

This paper discusses climate change in the Cenozoic by constructing a global carbon cycle model which is based on the GEOCARB-type model. Major improvements over previous models in this study are as follows. Previous models have not considered CO2 behavior at subduction sufficiently. They do not distinguish at subduction zones between the CO2 degassing from a back-arc basin (BAB) and that from an island-arc, although their degassing mechanisms may be different and should be treated separately. Also, previous models might overestimate the effect of silicate weathering in the regions of the Himalayan and Tibetan Plateau (HTP) on CO2 drawdown. Recent studies have revealed that this is smaller than previously presumed. Thus, we deal with these two kinds of degassing independently, and estimate the contribution of silicate weathering based on their studies. They are incorporated into the model. The model results indicate that: (1) the contribution of silicate weathering in the HTP region is small; (2) the warming from late Oligocene to early Miocene might be due to the CO2 degassing from the BAB; (3) the cooling event in the middle Miocene (15 Ma) is caused by a large amount of the organic carbon burial; (4) the CO2 variation is well consistent with the other studies of CO2 estimate, especially with the recent studies of CO2 estimate from the Miocene which indicate a relatively low level of CO2; (5) the age discrepancy between the CO2 peak in our model and the period of the Miocene Climatic Optimum might be attributed to the uncertainty of estimate of the BAB production rate, as a result of which the estimate should be revised. The model does not reconstruct the cooling trends from the middle Miocene (about 15 Ma) and the cooling event at the Eocene/Oligocene (E/O) boundary. This mismatch cannot be explained by the uncertainty of parameter estimates. Concerning the former event, the CO2 increase of the middle Miocene in our model may be consistent with increased volcanic activity resulting in a large amount of CO2 degassing. Therefore, it could be indicated that the coolings from 15 Ma and at the E/O boundary are attributed to the change of latitudinal temperature distribution caused by the variations of the oceanic environments, because the current carbon cycle models are not able to consider factors other than the CO2 greenhouse effect in estimation of surface temperature. However, the change of the temperature distribution on the surface itself does not affect the global averaged temperature. This assumption might not be precise because of the effects of in-depth heat exchange and other climatic factors. Nevertheless, a numerical test of the latitudinal sea surface temperature distribution based on observed δ18O records indicates that these effects are not critical at least for the coolings at the E/O boundary and from 15 Ma. Thus, the result of our model still reflects the reasonable mean temperature at least as a global one, and at the same time, the accurate reconstruction of the above two coolings might be beyond our carbon cycle model.

This paper presents the results of the scanning electron microscopic (SEM) analysis of quartz grains from a selection of samples at Site 1166. Ocean Drilling Program Leg 188 drilled Site 1166 on the Prydz Bay continental shelf, Antarctica, to document onset and fluctuations of East-Antarctic glaciation. This site recovered Upper Pliocene–Holocene glacial sediments directly above Cretaceous through Lower Oligocene sediments recording the transition from preglacial to early glacial conditions. SEM analysis of quartz grains at Site 1166 was used to characterize the glacial and preglacial sediments by their diagnostic textures. Angular edges, edge abrasion as well as arcuate to straight steps, are the most frequent features in glacial deposits. The highest frequency of grains with round edges is present in Middle–Late Eocene fluvio–deltaic sands. However, angular outlines, fractured plates with subparallel linear fractures and edge abrasion indicating glacier influence are also present. Preglacial carbonaceous mudstone and laminated gray claystone show distinctive high relief quartz grains and some chemical weathering on grain surfaces. The results of the microtextural analysis of quartz grains are used to verify some critical periods of ice sheet evolution, such as the transition from the East Antarctic preglacial to glacial conditions on the continental shelf from Middle/Late Eocene to Late Eocene/Early Oligocene time.

Floodplain deposits from the Carboniferous Tupe Formation of western Argentina contain a low-diversity ichnofauna of invertebrates and plants. The assemblage consists of Archaeonassa fossulata, Didymaulichnus lyelli, Helminthoidichnites tenuis, Palaeophycus tubularis, Planolites isp., and root traces. This ichnofauna is characterized by the dominance of very simple forms, superficial or very shallow trace fossils, combination of locomotion, grazing, and dwelling structures, and production by arthropods and vermiform organisms. Primary sedimentary fabrics are disturbed only by plant trace fossils while animal trace fossils are mostly restricted to bedding surfaces, resulting in the virtual absence of bioturbation. The poorly-defined morphology of the ichnofossils, and the absence of backfilled striated trace fossils and structures indicative of subaerial exposure suggest subaqueous production. The envisaged depositional environment is a freshwater body developed in a floodplain and overfilled by overbank deposits. A review of floodplain ichnofaunas documented from the stratigraphic record indicates that two recurrent assemblages may be recognized. The first assemblage is characterized by low to rarely moderate diversity of invertebrate trace fossils, moderate to high diversity of vertebrate structures, and common presence of meniscate backfilled structures, bilobate trace fossils with scratch marks, arthropod trackways and tetrapod trackways. It is regarded as an example of the Scoyenia ichnofacies developed in desiccated floodplains. The second type of floodplain assemblage, illustrated by the example documented in this paper, is characterized by grazing trails, locomotion trails and dwelling burrows, low to rarely moderate ichnodiversity, simple trace fossils, and superficial to very shallow structures. Although formed in floodplain environments also, this type of assemblage is remarkably different from the Scoyenia ichnofacies. It is here regarded as an example of the Mermia ichnofacies. Basic features of these ichnofaunas reflect subaqueous production of the assemblage. The lower ichnodiversity of these floodplain assemblages in comparison with their equivalents from lacustrine basins is probably an expression of the less stable conditions and temporary nature of floodplain water bodies. Our study supports the view that ichnofacies are not indicators of sedimentary environments but reflect sets of environmental factors.

Earlier workers have established sea level curves for the Ashgillian–Llandovery sequence on Anticosti Island, Quebec, Canada, based on sedimentology and on brachiopod and reef communities. The complete Anticosti sequence has been collected for conodonts to provide a database of over 77 600 conodonts derived from 272 samples through the 800–1100 m sequence. This paper uses a statistical analysis of the database to establish the pattern of conodont communities and their interpreted water depths. This allows the establishment of a eustatic sea level curve for the sequence. This curve is in general agreement with those of the earlier workers, but is more detailed and better constrained stratigraphically given the large sampling program. The curve reflects more oscillating sea level changes for the whole sequence than those constructed earlier, and different water depths for certain intervals from those established earlier. The curve is valuable given that the Anticosti sequence is one of the most complete in the world for this interval, and its divergence from global eustatic curves for this interval is noted.

This paper uses a multi-proxy approach involving pollen, plant macrofossils, speleothem isotopes, and alluvial history of streams to reconstruct the history of prairie expansion and contraction along the prairie-forest border of southeastern Minnesota, USA. Early Holocene forests were replaced by prairie along this border, but eastward expansion of prairie stalled for 2000 yr when the prairie-forest ecotone stabilized. Prairie invaded the area from the west 8000^9000 yr B.P., but mesic forest remained less than 100 km to the east until about 6000 yr B.P. Changes in N 13 C values in speleothem calcite, that reflect the rise of C4 grasses, correlate well with the presence of C4 grass species identified in the plant macrofossil record. Periods of large floods correlate with speleothem evidence of dry summers, increased cool-season precipitation (both resulting in less plant cover to absorb moisture), and change to prairie vegetation. fl 2002 Elsevier Science B.V. All rights reserved.

Fore-reef carbonate production is important but is poorly known as a result of methodological limitations. This paper reports on the development of a regional census-based method to calculate the average carbonate production of tropical–subtropical, coral-dominated fore-reefs. The estimates are based on coral cover and extension rates by growth form of fore-reefs with framework and biodetrital facies. Ecological data from many parts of the Indopacific and procedures to evaluate ramose coral data are most needed to further develop the method. The first estimates suggest that the common production in very shallow fore-reefs with dense ramose coral framework is around 10 kg CaCO 3 m −2 yr −1 or more. An analogous estimation suggests that shallow biodetrital fore-reefs produce around 1.5 kg m −2 yr −1 . The production rates decrease exponentially with depth. Fore-reef production is an important component of the global carbonate budget, but remains difficult to assess.

This paper presents the results of a survey of the contemporary diatom distributions in four tidal marshes of eastern Hokkaido, northern Japan. Distribution of living diatom cells, as defined by cluster analysis, have relations to vegetation and substratum, and clearly to tide level. Comparison between living and dead diatoms in each cluster provides synecological information relating to diatom taphonomy in the tidal wetland environments. Four assemblages are recognized and they are summarized as follows. (1) An upland assemblage consisting of autochthonous freshwater diatoms adapted to relatively dry conditions. (2) A high marsh assemblage formed at or slightly above mean high tide level (MHTL) with only few allochthonous components. (3) A low marsh assemblage formed below MHTL. Dead valves within this assemblage are repeated widely redistributed by tidal processes. This assemblage is therefore a ‘mixed assemblage’ comprising a combination of allochthonous and autochthonous diatoms. (4) A tidal flat assemblage. On death diatom valves in tidal flat are immediately redistributed by tidal currents, and the dead diatom assemblage here has the characteristics of an ‘autochthonous’ or ‘residual’ assemblage. Autecological perspectives based on the distribution patterns can advance these interpretations. Dead valves of the epiphytic diatom Cocconeis scutellum, which possesses a raphid valve (R-valve) and a rapheless valve (P-valve), are common on two transects but only P-valves are widely distributed beyond the seaweed zone which represents the actual habitat of this species. Such selective processes are related mainly to the life form characteristics of monoraphid species: only R-valves remain attached to their substratum on death. The tychoplankton Paralia sp. is also a widely distributed species. In the case of Paralia, their long chains float more readily than other specimens are transported easily by tidal currents, and then trapped in entire tidal environments. These observations suggest it is likely that concentrations of only P-valves of C. scutellum or Paralia in the tidal marsh deposits should be treated as allochthonous components in the diatom assemblage.

The early Palaeogene in the history of the Earth is noted for large-scale plate reorganisation believed to be associated with a changeover from the Laramide tectonic regime (‘Old’ crustal configuration) to the Himalayan tectonic regime (‘New’ crustal configuration). This tectonic change possibly proved to be a turning point in the evolution of Lithosphere, and ushered in drastic changes in the physical environment and evolutionary course of Biosphere in the Cenozoic. The consequent changes in the sedimentary environment and biotic development during Early Palaeogene have been pointed out for the Indian Ocean region. This paper examines the biostratigraphic data of the Early Palaeogene (Late Palaeocene–Middle Eocene) succession of the South Shillong Plateau, in the light of climatic and oceanic changes, and explores the possible role the regional tectonic changes may have played in shaping the course of environmental and biotic development preserved in the rock record of the Sylhet Limestone Group. An attempt has also been made to propose a model to explain the underlying tectonic changes in the Shillong Plateau. The biostratigraphic data from the area of investigation indicate that the major stratigraphic sequences recognised in the Sylhet Limestone Group can be broadly correlated with the stratigraphic succession of the Early Palaeogene identified in the Indian Ocean region. The succession of the sedimentary facies in this region seems to be the result of sea-level and climatic changes controlled by major tectonic reshuffling. From this correlation, it appears that the litho and biostratigraphic markers of the Sylhet Limestone were created by sea-level and climatic events related to tectonic changes occurring in the adjoining Indo-Burmese orogen as part of the large-scale global plate reorganisation mentioned as above.

The island of Viti Levu is located on the Fiji Platform in an area that has been tectonically active since at least the Late Eocene. The geological history of Viti Levu during this time is one of the competing influence of tectonics, volcanism and eustatic sea-level change in shaping the preserved stratigraphic, and therefore palaeogeographic record. The focus of this paper is the palaeogeographic evolution of Viti Levu from the period following the deformation of the Tuva Group and all older rock units of the Vityaz arc (around 7.5 Ma) to the present. Initial sedimentation during following the deformational event was influenced by the sinistral oblique-slip deformation associated with anticlockwise rotation of the platform. This tectonically dominated period of island evolution saw the establishment of a number of sedimentary basins, many of which continued to receive sediments through until at least the earliest Pliocene. From 6.5 Ma onward, volcanic activity became the main influence on the stratigraphic record, although evidence for major eustatic events (Miocene–Pliocene boundary) are recorded in some sequences. Toward the end of the Early Pliocene, tectonic uplift of Viti Levu resulted in a poor geological record for this time. The Quaternary stratigraphic record reflects relatively minor, mostly eustatic events in coastal areas around major river systems.

Two types of laminated sediments are compared in this paper: the Kimmeridgian bituminous laminites of Orbagnoux (French Southern Jura Mountains) and the present-day ‘kopara’ of the French Polynesia atolls or Kiritimati (Christmas) Island from the Pacific Ocean. The kopara is made of laminated sediments, several tens of centimetres thick, that cover the floors of most shallow ( 3 -rich laminae. The top few centimetres host a succession of bacterial populations, from aerobic to strictly anoxic. Most carbonate grains are precipitated in situ, due to bacterial activity (s.l.). The Kimmeridgian bituminous laminae of Orbagnoux are partly made of flat stromatolites that show many similarities with the kopara. This analogy allows us to refine the interpretation of the Southern Jura platform where laminated, organic matter-rich, carbonates were deposited in many places.

The Salar Grande is a 45-km-long (N–S axis), 4–5-km-wide, fault-bounded (pull-apart) Neogene forearc evaporitic basin, located in the Cordillera de la Costa of northern Chile whose sedimentary record is composed almost exclusively of a massive halite salt body. Underground waters coming from the east (now the Precordillera and Altiplano) were progressively enriched in solutes by interaction with volcanic rocks. These fluids drained into a lacustrine system located in the Depresion Central (in the Llamara–Quillagua area) and thick sequences of diatomites, carbonates, evaporites and clastic sediments were deposited. These lacustrine areas eventually dried out and became a salar with anhydrite and halite. During this stage (Late Miocene–Pliocene), evolved brines of the Llamara–Quillagua area migrated eastwards through structural paths, reaching the Salar Grande basin which acted as a final sink. A proof of this connection is the anhydrite level that links the western Llamara and southeastern Salar Grande areas. The accessory minerals and geochemical signatures in the rock salt are a record of the inputs arriving to the former lake and reflect variations in climate, and in tectonic and volcanic activity. The arrangement of halite textures along the sequence shows an evolution from a very shallow ephemeral saline lake (some cm–dm deep on average) to a salar where interstitial processes controlled by phreatic brines dominate. This evolution is coherent with a slight increase in the terrigenous content of the rock salt, and documents the increasing aridity of the climate as a response to the tectonic uplift of the Andean Ranges. In Pliocene times pore brines were definitively lost as a response to the downfall of the water table generated by the beginning of the exorheism due to the opening of the Loa River canyon towards the sea. The aim of this paper is to describe the Salar Grande through the study of its geological setting and its salt record. A detailed description of the salar will enable us to reach valuable conclusions about environmental conditions in the area during the Neogene, prior to the opening of the hydrologic system to the Pacific Ocean.

Taphonomy is important to coastal paleoecologists because processes acting on diatom thanocoenoses tend to work towards obscuring original ecological relationships between diatom assemblages and the environment. The purpose of this paper is to briefly describe diatom taphonomy and present a method for quantitative reconstruction of environmental parameters from salt marsh diatom assemblages. The main hypothesis for this study is that major environmental and taphonomic processes (e.g., tides) act in predictable ways to distribute living and dead diatoms along environmental gradients. To test this hypothesis, a modern transect was established across a large salt marsh in southwestern Puget Sound for the purpose of determining modern species/environment gradients and calibrating species assemblages to environmental variables. Canonical correspondence analysis (CCA) relates modern species assemblages to environmental gradients, and weighted averaging calibration is used to develop transfer functions for predicting environmental information. CCA showed that the effect of salinity and elevation on the species distributions is significant, indicating that environmental processes control the distribution of sedimentary diatoms across the salt marsh surface in predictable ways. Salinity was strongly correlated with CCA Axis 1 and elevation with Axis 2. The calibration results indicate that, although mixing of allochthonous and autochthonous diatoms does occur, salt marsh diatom assemblages reflect major environmental gradients in Puget Sound salt marshes and can be effectively used for quantitative reconstructions of former environmental conditions.

The calcitic shells of non-marine ostracods are sources of geochemical information that have the potential to record changes in the water chemistry of closed-basin lakes resulting from variations in the hydrological budget within the catchment. In particular the uptake of Sr and Mg into the shell has been shown to be a function of salinity, and salinity and temperature, respectively. This paper assesses the trace-element chemistry records from 4 short (1.5–2.8 m) cores from Lake Patzcuaro, central Mexico, in the light of a detailed limnological study of the lake. The following three environmental factors are believed to have influenced the interpretation of the trace-element chemistry record: (i) salinity: the salinity of Lake Patzcuaro lies close to the calcite branchpoint, below which the linear relationship between Mg/Ca or Sr/Ca and salinity has been lost in the fossil record; (ii) environmental stresses: e.g. low HCO3− concentrations, produced poorly calcified valves. This study found this had no significant effect on the trace-element chemistry results; and (iii) solute composition of the host water: changes in the solute concentration of inwash waters played a primary role in determining major water chemistry changes within the lake.

Sulawesi and Borneo are located in the middle of the Indonesian Archipelago, an area which has been extremely tectonically active throughout the Cenozoic. This paper compiles current knowledge on the geology and palaeogeography of this complex region and includes the first attempt to synthesise palaeogeographic data onto plate tectonic reconstructions. Construction of palaeogeographic maps helped to identify some of the strengths and weaknesses of current plate tectonic models for the region, thereby highlighting areas where further geological research is required. Palaeogeographic maps presented, using plate tectonic reconstructions as a base, illustrate the evolution of Borneo and Sulawesi and highlight important changes in the environment during the Cenozoic. The Tertiary geological history of eastern Borneo and Sulawesi is inextricably linked to the progressive accretion of continental and oceanic material from the east, onto the eastern margin of Sundaland, and to the resultant development of volcanic arcs. Large tracts of western Sulawesi, eastern Borneo, the East Java Sea and the Makassar Straits formed an extensive basinal area throughout much of the Tertiary. Implications for plate tectonics, exploration for natural resources and biogeography are discussed from the palaeogeographic reconstructions of Sulawesi and Borneo.

The available records of inflows to Lake Eyre cover only forty five years. Their quality is questionable. As longer time series of precipitation records are available, the observed series of inflows to Lake Eyre can be extended with the help of a rainfall-runoff model. Further reconstruction of the inflow series can be achieved by examining local evidence or with the help of proxy data. However, the limitations of these extensions and reconstructions of inflows are severe. The inflows to Lake Eyre could be considered one of the most convincing manifestations of hydrological uncertainty. However, it is apparent that major flooding episodes in the Lake Eyre Basin are most often associated with La Nina phases of the El Nino–Southern Oscillation (ENSO) phenomenon. The paper presents a hydrological description of the Lake Eyre Basin and large-scale contemporary and palaeo climatic patterns which affect the water balance of the catchment. A simple water balance model has been constructed to determine storages of the lake when annual evaporation reaches equilibrium with annual runoff.

Lake Eyre is presently an ephemeral playa-lake in an extremely large (1.3 million km2 internal drainage basin), with most of its inflow derived from monsoon-watered northern Australia. The hydrologic state of the lake has varied in the past, in response to climate change, from a perennial lake up to 25 metres deep to a groundwater-controlled playa, marked by substantial sediment deflation. This paper is concerned with the stratigraphic record of the last 60 ka of that hydrologic history, particularly the character and age of a playa-marginal unit formed by deflation from the playa and of stranded high beach ridges. A major deflation episode between 60 and 50 ka excavated the present Lake Eyre basin and deposited a gypsum- and clay-rich aeolian phase (the Williams Point aeolian unit) at a number of sites around the lake. After deflation ceased a thick secondary gypsum profile developed on the dune early in oxygen-isotope stage 3; evidence for the state of Lake Eyre at this time is equivocal. Preliminary results from a substantial suite of amino acid racemization (AAR) analyses of mollusc shell and bird eggshell samples from beach ridges at +5 and +10 m Australian Height Datum (AHD) suggest that they are oxygen-isotope stage 5 in age. Sedimentologic evidence suggests that it is unlikely that the shells are reworked from older deposits. These AAR results apparently conflict with early oxygen-isotope stage 3 thermoluminescence (TL) dates from the +5 m AHD beach ridge (Nanson et al., this volume). However, the age difference is not substantial, the calibration of the AAR is still at a preliminary stage and only one site was sampled for both techniques. Further stratigraphic and chronologic work is required to fully assess the apparent discrepancy. Between about 30,000 and 12,000 yr B.P. Lake Eyre was at least as dry as it is today. At many sites around Madigan Gulf a lunette-like, playa-marginal, aeolian unit (the Shelly Island unit) was deposited during this period, formed by material deflated from the playa floor. Forty AMS radiocarbon dates span the period 35,000 to 10,000 yr B.P., from the Shelly Island unit (11) and from aeolian sediment close to playa level (29), indicating that the lake was dry during this period. This evidence conflicts strongly with 2 TL dates from latest oxygen-isotope stage 3 and oxygen-isotope stage 2 from the +5 and +10 m AHD beach ridges (Nanson et al., this volume). Additionally, the AAR results from the high beach ridges cannot be reconciled with these TL dates. After 10,000 yr B.P. a minor lacustral phase occurred until the modern ephemeral playa regime became established at 3000–4000 yr B.P.

This paper reports on the first subsurface core taken from an alluvial fan in the interior plains of western Canada. Sedimentary structures, grain size, grain roundness, loss on ignition, charcoal abundance, bulk authigenic geochemistry, colour, mineralogy and microscopic charcoal identifications show that a fine-grained fan developed through a succession of depositional environments. Within each environment, sediment erosion, transportation and deposition processes were conditioned by changing dominant partial area contributions and complex geomorphic responses. Neither the rate nor the processes of aggradation have been constant through time. Succession from one depositional environment to another involved the crossing of geomorphic thresholds. While climate may have affected sediment yield and therefore the timing of threshold crossings, the basic sequence was controlled by aggradation alone. The sensitivity of this site to climate change is thus overwhelmed by internal processes.

This paper describes multiple layers of ice-rafted debris and an ice-scour structure in Early Permian marine strata within the Shoalhaven Group of the Sydney Basin, New South Wales, Australia. Strata were deposited on a high-latitude, glacially influenced continental margin during the final stages of Late Palaeozoic glaciation between 277 and 260 Ma. Poorly sorted ice-rafted debris, forming layers up to 1.25 m thick, is common within inner to outer shelf and continental slope facies of the Shoalhaven Group. More than 120 layers can be identified. These are argued to record the enhanced delivery of debris by icebergs drifting north from marine-based Antarctic ice margins. Deformation structures in associated sediments are interpreted as iceberg scours and ice keel turbates. Associated glendonites record early diagenesis of organic-rich sediment and bottom water temperatures close to freezing. A speculative hypothesis relates layers of ice-rafted debris within the Shoalhaven Group to multiple episodes of accelerated calving at the margins of a marine-based Early Permian ice sheet in East Antarctica. These events may be analogous to late Pleistocene Heinrich events, when huge armadas of icebergs were released from the marine-based Laurentide Ice Sheet and triggered abrupt changes in ocean circulation and climate. Similar forcing may have characterized the Early Permian ice-ocean system. Regardless of the climatic significance of ice-rafted layers, this is the first time such facies have been documented in the pre-Pleistocene literature; to date, few ice scour structures, and no ice keel turbates, have been reported.

This paper presents TL age estimates of Pleistocene raised marine terraces from southern Calabria (southern Italy). It focuses on the dating of last interglacial shallow-marine sand deposits, including several Tyrrhenian key reference deposits whose stratigraphic assignment is based on biostratigraphic evidence (presence of a Strombus bubonius fauna) and geochronometric data (amino-acid data calibrated with U Th dates on coral). The TL age estimates are obtained on alkali feldspar coarse grains using their blue TL emission. They are in good agreement with the IR-OSL age estimates obtained on the same feldspar samples. Our feldspar TL method is tested on two Tyrrhenian key reference sites, Ravagnese and Bovetto, in the Reggio di Calabria area. Their measured TL age estimates (97 ± 11 ka and 100 ± 10 ka) are lower than their estimated geological age (i.e. Oxygen Isotope Substage 5e). The correction for long-term fading suggested by Mejdahl (1988), is tested on these two samples using a lifetime of 446 ka as estimated from both Calabrian and Miocene sand collected within the same area. This correction would yield preliminary TL ages (116 ± 13 ka and 116 ± 12 ka) that are in better agreement with the expected geological age. The application of our TL method to paleoshorelines lying below the Tyrrhenian reference shoreline of Ravagnese-Bovetto, yields stratigraphically consistent TL age estimates. The TL method is also applied to two supposedly pre-last interglacial paleoshorelines which are geomorphologically older than the Tyrrhenian reference shorelines. They remain however chronologically undifferentiated, both by the TL and the amino-acid methods. Finally, the preliminary feldspar TL results obtained on the Miocene and the Calabrian sand deposits (> 1 Ma), suggest that our feldspar TL method is limited, in the SW Calabrian area, to about 200 ka.

Current latest Pleistocene-early Holocene palaeoclimatic reconstructions for the Adriatic Sea region (Eastern Mediterranean) are still controversial, suggesting either dry or humid conditions for the interval between 18 and 8 ka B.P. These reconstructions are derived from either marine or terrestrial records which are rarely considered together and are often based on only few datapoints. Intercorrelation of both marine and terrestrial, high time-resolution records is required to obtain a more realistic reconstruction. In this paper a palynological approach to such a high resolution, land-sea correlation is presented. Sediments from a well-dated core in the southern Adriatic Sea have been studied for their dinoflagellate cyst and pollen content. Changes through time in the composition of the dinoflagellate cyst association, provide information about palaeoenvironmental change in the marine realm, whereas changes in the pollen association provide information about environmental changes on the continent. Correlation of these records indicates that from 18 to 13.2 ka B.P. (glacial period) cold, dry climatic conditions existed in the Adriatic Sea region. At the end of this period increased discharge by the Po river can be identified, corresponding to a melting phase of glaciers in the Alps and Apennines. Between 13.2-11 ka B.P. (Bolling/Allerod) temperatures increased. Two additional intervals with steadily increasing Po river discharge have been identified between 12.8-12.2 ka B.P. and 12-11.2 ka B.P. with maximum discharge at 12.2 ka B.P. and at 11.2 ka B.P. These increases in discharge are probably due to enhanced winter precipitation since vegetation reconstructions, based on pollen records from terrestrial deposits, indicate no increase in spring/summer precipitation; moreover, there is no evidence of increased melting of glaciers in the Alps and Apennines in these intervals. Between 11-10 ka B.P. (Younger Dryas) the climate became cold and dry again. At the end of the Younger Dryas a fourth interval with increased Po river discharge can be observed which correlates to a second melting phase of Alpine and Apennine glaciers. After 10 ka B.P. (Holocene) climatic conditions became more warm and humid.

A 12.4 m core taken in Lake Bangong provides a continuous Holocene climatic record. We summarize information on changes in stable isotope and radiocarbon balances in the lake, hydrobiology and vegetal cover in the catchment, deduced from detailed analytical results given in the three preceding papers. The Bangong record is then compared with the environmental history of the neighbouring Lake Sumxi also constructed from multidisciplinary analyses. The two records show a major environmental change at ≈ 10-9.5 ka B.P., attributed to a rapid strengthening of the summer monsoonal circulation which led to wet-warm conditions. This event was followed by a long-term trend toward aridity which culminated around 4-3 ka B.P.. In Western Tibet, maximum monsoon rainfall seems to have occurred from ≈ 9.5 to 8.7 ka B.P. and from ≈ 7.2 to 6.3 ka B.P., as two wet pulses separated by a reversal event centered on 8.0–7.7 ka B.P. Our results broadly agree with the records from Lake Seling in Central Tibet, and Lake Qinghai at the plateau's northeastern margin, and with palaeoclimatic studies in western China which document conditions wetter and warmer than those of today during the early-middle Holocene. The environmental fluctuations recorded in western Tibet appear in phase with climatic changes recognized in tropical North Africa, suggesting that the 8.0–7.7 ka B.P. and the 4.0–3.0 ka B.P. dry events were caused by abrupt disequilibrium in the climatic system.

The aim of this paper is to examine the mammalian faunas of the Neogene of Spain and of East Africa with a view to understanding the relationships between the Neogene faunas of the two regions. The available data indicates that during the Neogene, faunal similarities between Iberia and East Africa varied greatly, at times the resemblances being relatively great (high number of genera in common), at others the similarities being weak (low number of genera in common). Changes in faunal similarity appear to be related to latitudinal fluctuations in the position of the boundaries of the Proto-Ethiopian and Proto-Palaearctic zoogeographic realms. Periods of greater faunal similarity coincide with a northerly position of the boundary zone, while periods of greater faunal dissimilarity occur when the boundary zone is located in a southerly position, as it is today. We related these changes in the position of the boundary zone between zoogeographic realms to geotectonic, climatic and astronomic changes which affected the globe.

Trend surfaces can be produced by a number of mathematical techniques and have been used widely to depict the regional variation of various geological parameters. In this paper, it is demonstrated that trend surfaces can be constructed by a simple graphical method and may be applied successfully to palaeoenvironmental reconstructions using elevation contour of tilted or folded contacts. Two case studies are discussed to illustrate different aspects of the technique. In the first example, the upper contact of a shallow marine sandstone outcropping over an area of roughly 4000 km 2 in the southwestern part of the Sydney Basin (Australia), is restored by means of a first order trend surface. This reveals the palaeotopography as a sinuous shoal trending towards the northnortheast. The second example, from the Beaufort Group of the Karoo Basin (South Africa), restores the basal contact of a fluvial sandstone by means of a second order (quadratic) trend surface. The restored surface portrays the individual thalwegs and islands of a braided stream system over an area of about 4 km 2 .

In this paper we outline the Triassic to Jurassic history of the eastern Ogaden Basin as obtained from micropalaeontological studies. Continental sediments bearing Upper Triassic spores and pollen are overlain by Tethyan shallow water limestones yielding foraminifera and dinoflagellates of Callovian aspect. Flooding of the carbonate platform close to the Callovian Oxfordian boundary brought about replacement of larger foraminiferid assemblages (adapted to warm, clear, oligotrophic waters) by smaller benthic foraminiferid assemblages (adapted to deeper, muddier substrates). A brief influx of early planktonic foraminifera (the first recorded from east Africa) provides evidence for a connection with oceanic waters of the western Tethys. These changes are attributed to a series of major transgressions (c. basal Callovian/Oxfordian boundary) which, in turn, coincided with the initiation of sea floor spreading during the opening of the Somalia Basin of the western Indian Ocean. The spread of early planktonic foraminifera may have been enhanced by the breakup of Gondwana and the formation of new ocean basins.

Two main moraine complexes are usually defined in the northwestern Alpine piedmont: the External Moraine Complex (EMC) dated to the penultimate glaciation (“Riss” sensu lato) and the Internal Moraine Complex (IMC) dated to the last glaciation (“Wurm”). Until recently the prevalent concept was that these two complexes had been built by glaciers originating in the central Alpine zone. This paper presents a new palaeogeographical diagram, based on mapping and petrographical studies of these two moraine complexes, and especially on the relationships between Alpine and Jura tills. We reach the following conclusions. 1. (1) The Jura glaciers were independent of the Alpine glaciers during the two last Pleistocene glaciations. 2. (2) The Jura Mountains formed a topographical barrier blocking and modifying the Alpine glacier advance towards the northwest, with the result that ◦ -during the Wurmian glaciation, the maximum elevation (1200 m a.s.l.) of the Alpine glaciers on the eastern margin of the Jura was too low to allow Alpine ice to enter the Jura; and ◦ -during the “Rissian” glaciation, the greater thickness of the Alpine glaciers resulted in their penetration only into the lower marginal zone of the Jura. 3. (3) Thus, in the studied area, the central Alps were not the only centre of ice dispersal during the two last Pleistocene glaciations: on the northwestern Jura slopes, the corresponding moraine complexes were mainly built by glaciers emanating from the central Jura.

Lake Tanganyika, situated in the Western Branch of the East African Rift System, shows a slightly positive water budget and generates a small outflow (through the Lukuga River), dependent mainly on the Ruzizi River inflow from Lake Kivu in the northern part of the basin. Conditions more arid than those presently observed, closed the Kivu Basin from 3800 to 1300 yr B.P. Previous studies esimated that the closure of the corresponding Tanganyika Basin lowered the lake level by 75–150 m. In this paper we present the results of isotopic and morphologic analyses of fossil stromatolites. The stromatolites formed as thick incrustations on hard substrates and are found at depths between 6 and 60 m below the modern lake level. Their isotopic composition (18O, 13C, 14C) very precisely document Late Holocene water levels and hydrologic fluctuations in the Lake Tanganyika Basin, with reference to the actual situation. A major low stand, at 10 m below present level, is identified from 3400 to 1900 yr B.P., with a rapid recession and gradual rise to modern levels. Maximum δ18O values (vs PDB) in the stromatolites rose from ca. 3.5% (at 3400 yr B.P.) to 6% (at 2500 yr B.P.), then decreased progressively to 1.6% (at 1300 yr B.P.). These values are interpreted as a maximum aridity episode culminating at ca. 2500 yr B.P., at which time a negative precipitation/evaporation (P:E) ratio resulted in a much higher residence time of paleolake waters and thus a noticeable enrichment in 18O. The observed decoupling of the isotopic ratio (18O/16O) and water volume responses is thought to be linked to the inertia of the large rift aquifers which controlled the paleolake level.

All major ephemeral rivers of Australia lie in the Lake Eyre basin. Dry for years, on occasions they carry enormous floods, with annual volumes of 40 km 3 and instantaneous discharges of the order of 30,000 m 3 s −1 . Mean annual runoff of the basin is 4 km 3 or 3.5 mm, significantly less than the 57 mm for the whole of Australia. This paper examines Lake Eyre and its drainage basin, describing the historical hydrology of the catchment, both in terms of instrument records and inflows hindcast using a model based on the technique of coral fluorescence palaeohydrological reconstruction. Coral fluorescence is a function of nearby-river discharge, and can be used to reconstruct annual river outputs reconstruction. Coral fluorescence is a function of nearby-river discharge, and can be used to reconstruct annual river outputs beyond the instrument period. The Burdekin River catchment runoff history is strongly paralleled by the volumes of Lake Eyre inflows during the period of common reliable instrument gaugings. The Burdekin runoff data have been extended back to 1735 A.D. using the correlation between river discharge and annual growth-band fluorescence in an old coral from Pandora Reef, off the North Queensland coast. For the instrument period 1952 to 1980, 73% of the variance between coral fluorescence and Burdekin discharge is common. During the period 1949–1980, 41% of the variance between coral fluorescence and Lake Eyre inflow data is common. Modelled inflows to Lake Eyre for the period 1885–1948 are based on the latter data set.

A rise of sea level between 0.3 and 0.9 m by the end of the next century, caused by predicted greenhouse climate warming, would endanger human populations, cities, ports, and wetlands in low-lying coastal areas, through inundation, erosion and salinization. The consequences of a global sea level rise would be spatially non-uniform because of local or regional vertical crustal movements, differential resistance to erosion, varying wave climates, and changeable longshore currents. Although many factors can influence sea level, leading to a noisy record, various studies utilizing tide-gauge data find an average global rate of sea level rise of 1–2 mm/yr, over the last 100 years. This trend is part of a general rise over the last 300 years, since the low point of the Little Ice Age. Sea level rise may accelerate 3–8 times over present rates, within the next century. The permanently inundated coastal zone would extend to a depth equivalent to the vertical rise in sea level. Major river deltas, coastal wetlands and coral islands would be most affected. Episodic flooding by storm waves and surges would penetrate even farther inland. Beach and cliff erosion will be accentuated. Saltwater penetration into coastal aquifers and estuaries could contaminate urban water supplies and affect agricultural production. Research on relative risks and impacts of sea level rise on specific localities is still at an early stage. Development of a global coastal hazards data base, intended to provide an overview of the relative vulnerabilities of the world's coastlines, is described in this paper. To date, information on seven variables, associated with inundation and erosion hazards, has been compiled for the U.S., and parts of Canada and Mexico. A coastal vulnerability index (CVI) has been designed to flag high risk coastal segments. Preliminary results are presented for the eastern United States, as a test case.

Coastal cliffs up to 70 m high provide a nearly continuous section along depositional strike of a small Quaternary fan delta complex south of Conway Flat, north Canterbury, New Zealand. A gentle northeasterly dip permits observation of all facies of the complex, from the offshore prodelta to an emergent interdeltaic embayment facies showing beds with abundant rhizoliths, and in situ roots and stumps of large 8000-yr old podocarp trees. Coarse gravels derived from the Hawkeswood Range (650 m high), 5 km west of the sea cliffs, were transporte largely by debris flow processes into the Pacific Ocean towards the Conway Trough (800 m deep), 10 km to the east of the cliffs. Narrow (up to 1 km wide) Gilbert-type gravel deltas built elongate lobes into channels created by slumping and sediment gravity flows which deeply incised muddy prodelta deposits. Between the fan deltas, embayment facies are dominated by loessial sediment with sand:silt:clay ratios of about 7:68:25; thin sand beds are present. Prodelta sediments also are composed largely of redeposited loess. Loessial sediment came from the distant glaciated Southern Alps, transported both in air and along major rivers that produced broad plumes of suspended sediment in the ocean which were carried northwards by the prevailing longshore currents. Laterally adjoining the fan delta lobes, on several wave-cut benches within them, and scattered in the distal embayment facies are winnowed wave-sorted bars of fine gravel and sand. The proximal embayment facies includes sparse, poorly sorted, gravelly storm bars, gravelly fluvial crevasse deposits, and shallow broad tidal channel filled with loessial sediment and fine sand. Well-displayed trace fossils permit close correlation of ichnofacies with lithofacies and extend paleoenvironmental interpretation in this young deposit. Trace fossil associations and interpretations are described in the following paper in this journal.

This paper deals mainly with the Late Cretaceous La Luna Formation on the Venezuelan Andean Platform. The studied area (the so-called Transversale de Barquisimeto) is located at the contact zone between the Andes of Merida and allochthonous slabs thrusted from the Caribbean Domain and is crosscut by a major active transform fault (the Bocono Fault), which is part of the contact zone between the Caribbean and South-American plates. The La Luna Formation is made of dark, organic-rich, laminated limestones and shales and, though always appearing with black shale facies, is different in the areas located in the north or in the south of the Bocono Fault. We provide here some new information about the biostratigraphic frame of the La Luna Formation and of the overlying Colon Formation. In the studied area, the depositional environment of the La Luna Formation was certainly rather shallow (near storm wave base) and stratified. During deposition of La Luna Formation, dysaerobic to anoxic conditions prevailed, which may be linked with a regional anoxic event, perhaps related to seasonal upwelling along the northern coast of South America during Late Cretaceous time.

Correlative Late Precambrian strata of the Avalonian-Cadomian orogenic cycle, deposited after 670 and before 550 Ma are now widely dispersed around the margins of the North Atlantic. These contain several prominent diamictite horizons, long interpreted as “tillites”, within thick turbidite successions associated with volcanic horizons. The Granville Formation of the Armorican Massif in Normandy, France contains many pebby mud (diamicite) beds up to 20 m thick that have been interpreted as glaciogenic. Regionally, the Granville Formation occurs within the lowest part of the Upper Brioverian Supergroup which consists of several kilometres of turbidites and volcanogenic rocks. At Granville, diamictites can be traced along striked into deformed and intermixed graded conglomerates and mudstones. Diamictites are identified as debris flows generated on a submarine slope by the emplacement of gravel turbidites on a mud substrate and their mixing during downslope slumping. A glacial influence cannot be identified. In North America, the Conception Group of the Avalon Peninsula, Newfoundland, Canada, contains nearly 4 km of turbidites with a conformable sequence of diamictites (the Gaskiers Formation) near its base Massive and crudely-stratified diamicite beds ( The diamictite successions of the Granville and Gaskiers formations provide significant data regarding facies types, associations and the geometry of resedimented diamictite sequences in deep marine basins along active plate margins. Similar deposits at the same tectonic-stratigraphic horizon occur in New England and Africa. This paper emphasizes the difficulty of identifying a direct glacial influence on diamictite sedimentation in such settings and the need for a sedimentological reappraisal of other supposed late Precambrian “tillites” preserved in orogenic belts. This is a necessary first step prior to modelling late Precambrian paleoclimates.

This paper reviews attributes of Quaternary lakes and lake basins which are often important in the environmental prehistory of semideserts. Basin-floor and basin-closure morphometry have set limits on palaeolake sizes; lake morphometry and basin drainage patterns have influenced lacustrine processes; and water and sediment loads have influenced basin neotectonics. Information regarding inundated, runoff-producing, and extra-basin spatial domains is acquired directly from the palaeolake record, including the littoral morphostratigraphic record, and indirectly by reconstruction. Increasingly detailed hypotheses regarding Lake Bonneville, the largest late Pleistocene palaeolake in the Great Basin, are subjects for further testing and refinement. Oscillating transgression of Lake Bonneville began about 28 ka, the highest stage occurred about 15 ka, and termination occurred abruptly about 13 ka. A final resurgence of perennial lakes probably occurred in many subbasins of the Great Basin between 11 and 10 ka, when the highest stage of Great Salt Lake (successor to Lake Bonneville) developed the Gilbert shoreline — and when the Russell shoreline formed 500–600 km away, in the Carson Desert of the Lake Lahontan basin. The highest post-Gilbert stage of Great Salt Lake, which has been one of the few permanent lakes in the Great Basin during Holocene time, probably occurred between 3 and 2 ka. A set of eighteen general observations regarding geologic aspects of the palaeolake record in semidesert basins is helping to guide Quaternary studies in the Great Basin.

Prior to the past decade, freshwater sponges had not been utilized in paleolimnological studies. There were valid reasons for this: the taxonomy of the spongillid freshwater sponges of the world was in complete disarray; the ecological parameters of freshwater sponge species either were not known or were presented in scattered publications that were not readily available to paleolimnologists. The revisionary work of Penney and Racek finally brought order into the chaos of spongillid systematics. Shortly after the appearance of the Penney-Racek landmark monograph, Poirrier, and later Harrison, described the ecological parameters of North American spongillid freshwater sponges in a series of species-by-species treatments. Racek, in a body of pioneering studies, evaluated spicular remains of freshwater sponges in cores dating to 30,000 yr B.P. from several lakes, i.e., Lake Huleh, Lago di Monterosi, Laguna de Petenxil, while Harrison and colleagues characterized the past history of Lake Okeechobee (3000–4000 yr B.P.) and of Serendipity Bog, Graham Island, British Columbia (9400-8500 yr B.P.) using spicular components. It is now evident that freshwater sponge skeletal and reproductive structures can be used to characterize accurately past ecological conditions of freshwater habitats. In this paper, I will introduce the reader to the pertinent literature in freshwater sponge taxonomy, will characterize spongillid species into broad groups based upon their environmental parameters, and will summarize present paleolimnological studies using freshwater sponge remains as a diagnostic tool.

This paper argues that glaciomarine environments can be regarded as special, glacially-influenced types of continental margin environments (e.g. continental shelf, slope, rise and basin plain). Knowledge of the stratigraphic architecture and typical sedimentary sequences of non-glacial margins is becoming well-known but remains limited for those that have been glacially modified. The principal influences on sedimentation in these environments relate to the glacial sediment input (controlled by relief of basin margin, glacier thermal regime and ice flow dynamics) and depositional environments (influence of traction currents, substrate relief and proximity to nearby ice margins). Typical ranges of sedimentation rates can be established for glacially-influenced continental margin environments and these may provide a framework for ancient sequences. Starvation of sediment supply to glacially-influenced continental margins is common. The nature of sub ice shelf sedimentation, a model that has been applied to many ancient glacial sequences is critically reviewed; the significance of such sedimentation in the rock record has probably been exaggerated because of oversimplistic interpretations of diamictite sequences. Existing process models of glaciomarine sedimentation derived from study of modern environments are sometimes difficult to employ in investigation of ancient sedimentary sequences because simple lithofacies criteria and typical vertical profiles are not available to aid in interpretation. In addition compositional data emphasized by many workers for distinguishing glaciomarine from continental glacial diamict(ite)s frequently fingerprint sediment source and not mode of deposition. The importance of facies analysis methods for isolating depositional environments is illustrated by three examples of ancient glaciomarine sequences. These are the Early Proterozoic Gowganda Formation (∼2.3 Ga) of northern Ontario, Canada; the Late Proterozoic Port Askaig Formation (∼670 Ma) of Scotland and Ireland, and the Late Cenozoic Yakataga Formation (∼20 Ma to recent) of the Gulf of Alaska. These examples illustrate the significance of detailed genetic studies of ancient glacial rocks in the interpretation of palaeogeographic and tectonic settings. Diamictite units in ancient glaciomarine sequences cannot be easily interpreted in terms of climatic or ice advance/retreat cycles, because of the varied controls on diamict accumulation and diamictite preservation in marine basins.

During the Ordovician, the Armorican Massif is generally considered as a platform domain, a shallow marine environment characterized by endemic invertebrate faunas. However, approximately from the late Llanvirn to the end of the Llandeilo, different trilobite associations develop. Their geographic distribution seems to be mainly related to bathymetric variations. The interpretations proposed in this paper are supported by lithological and sedimentological data and comparisons with living marine crustaceans. The possible mode of life of some trilobites has also been taken into consideration; thus, at the eastern end of the Armorican median synclinorium, and south of Rennes (Martigne-Ferchaud synclinorium), the presence of Parabarrandia, a mesopelagic trilobite from open shelf, indicates amongst other things a marked increase of depth from west to east and from north to south. In the southeastern part of the Armorican Massif (Ancenis region), the development of a cyclopygid biofacies indicates the beginning of a slope opening onto a deep marine environment (South-Armorican ocean?). In some cases (Uralichas, Ectillaenus, Panderia), the exceptionally large dimensions of the dorsal exoskeletons would result from the low water temperature at high latitudes, which agrees well with the existence of a Gondwanan glaciation at the end of the Ordovician.

This paper deduces late Holocene eustatic sea-level changes from 14 C dates and present elevations of almost all Holocene raised coral reefs in the Ryukyu Islands (an active island arc), without the assumption of a constant uplift rate. Stable relative sea levels, are restored by using sea-level indicators, such as raised coral reef terraces, fossil coral, wave-cut notches, and beach rock. The oldest and the youngest 14 C ages of calcium carbonate fossils, collected from a depositional terrace-surface, show their formative period. When all relative sea-level changes of thirteen islands are compared, the Ryukyu Islands form three groups according to the oldest age in the formative period of the Holocene raised reef terraces in each island, that is 6500 yr B.P., 5000 yr B.P., and 3500 yr B.P. The youngest of the terrace-formative periods in the three island groups correspond with each other. One eustasy explains the seismic upheaval and the formative process of the terrace-surfaces of the three island groups. The eustatic sea-level trend in the Ryukyu Islands can be summarized as follows. From 6500 to 3500 yr B.P., the sea level continued to rise generally. Around 6500 yr B.P., 5000 to 3500 yr B.P., and 3500 to 1700 yr B.P., the rates of sea-level rise became slower. The sea level between 3500 and 1700 yr B.P. was stable and it has been the highest in the Holocene. At that time its height was less than 1.0 m above the present sea level. The Holocene uplift rate of each island is estimated to be half to three times as great as that of the last 125 000 years. The uplift rates of the three island groups in the late Holocene are inferred to have been decreasing exponentially. The crustal movement and the distribution of raised coral reefs are further discussed here.