Interglacial Age Research Articles

ESR Dating of Coral Reef Terraces on Curaçao (Netherlands Antilles) with Estimates of Younger Pleistocene Sea Level Elevations

Abstract A sequence of at least three Late and Middle Pleistocene coral reef terraces (Lower Terrace, Middle Terrace I and II), which are uplifted up to 45 m a.s.l., is conserved on Curacao. The less uplifted Lower terrace (elevation 6 to 12 m above sea level) consists of two different coral reef formations: the Hato unit and the underlying Cortalein unit. The discontinuity between these two superimposed units is typically marked by a strong difference in the degree of weathering. Samples of coral in growth position were collected from the Lower Terrace (Hato and Cortalein unit) and the Middle Terrace I. ESR ages indicate a Last Interglacial age of the Hato unit of about 122 ky BP, and a correlation with the Last Interglacial sea level maximum (stage 5e). The ESR age of the underlying Cortalein unit is about 216 ky BP (stage 7). Palaeo sea level calculations imply a correlation with the youngest of three Penultimate coral reef terraces located on the island of Barbados, which was uplifted more strongly th...

Homo erectus pekinensis?s age and environment??with discussion on the relationship among Homo erectus from Beijing, Nanjing and Chenjiawo

This paper inspects the relationship betweenHomo erectus from Beijing, Nanjing and Chenjiawo on the viewpoint of environmental variations. Pieces of evidence show that Nanjing and ChenjiawoHomo erectus lived in glacial age at the Marine Oxygen Isotope Stage (MIS) 16, whileHomo erectus pekinensis in major interglacial age at MISs 15-13. It is also recovered that the cave deposits in Tangshan, Nanjing, and Zhoukoudian, Beijing, as well as the deposits at theHomo erectus site in Chenjiawo, have undergone some similar development process. All of them originated from early-middle Middle Pleistocene, and have gone through the test of the major glacial age at MIS 16 and the major interglacial period at the paleosol stage S5. At the same time, they were also closely connected with some environment events, such as the uplift of the Qinghai-Xizang Plateau, the formation of glaciations and the loess accumulations.

Chemical weathering history of the southern Tajikistan loess and paleoclimate implications

Major chemical elements and Rb, Sr, Ba abundances were measured for loess samples from Chashmanigar loess-soil sequence in southern Tajikistan. And the degree of element loss and intensity of weathering of the samples were calculated. From these calculations we found that the paleosol horizons of the Chashmanigar section were chemically weathered to some extent and the weathering intensity of the soils is stronger than that of loess horizons, indicating that paleosols in southern Tajikistan were deposited in relatively warm and humid interglacial ages. In addition, the southern Tajikistan loess deposited before 0.9Ma BP was more intensely weathered than that deposited after 0.9Ma BP, which may imply the intensification of aridity in this area since 0.9Ma BP.

Holocene uplift rates and historical rapid sea‐level changes at the Gargano promontory, Italy

AbstractThis paper uses a combination of geomorphological and radiometric data from the northern coast of the Gargano promontory (comprising the Fortore River coastal plain and Punta delle Pietre Nere) to reconstruct Holocene uplift rates. The coastal plain consists of a sandy progradational beach sequence that extends seawards from the base of a relict cliff. This cliff probably marks the maximum position reached by the Holocene transgression. Altimetric data compared with the age of beach deposits and the available eustatic sea‐level curves indicate an average Holocene uplift rate of 1.5 mm yr−1. A similar uplift rate has been estimated by dating a bioherm constituted of calcareous algae, Vermetids and subordinately by Cladocora caespitosa (L.), which crops out in the locality of Punta delle Pietre Nere. This deposit, which was previously assigned an interglacial age, yielded a mid‐Holocene age by means of Th/U and 14C age determinations.Our observations also reveal evidence for coseismic deformation along the northern coast of the Gargano promontory during the last millennium. Vertical displacements of >0.5 m have affected the Punta delle Pietre Nere coastal block, and were preceded by periods of slow coastal subsidence, which increased rapidly shortly before a major earthquake. Copyright © 2002 John Wiley & Sons, Ltd.

Carbon flux during the last interglacial cycle in the inner continental shelf of the South China Sea off Hong Kong

Information obtained from previous studies has been used to study carbon flux during the last interglacial cycle in the siliciclastics-dominated inner continental shelf of the South China Sea off Hong Kong. The information included grab sampling surveys, many kilometres of high-resolution reflection seismic profiles and numerous boreholes. During the high sea-level stand of the Holocene and the last interglacial period, the inner shelf of Hong Kong was a net carbon sink. This is particularly so in the present day mainly through the discharge of anthropogenic sewage. The offshore dredging of mud and the offshore mining of sand and gravel deposits have nevertheless led to the release of methane and other gases either trapped beneath Holocene deposits or originating from the bacterial breakdown of plant matter within Pleistocene deposits contributing greenhouse gases. During the last glacial period, significant quantities of carbon dioxide formed by the dissolution of carbonates through acid-sulphate development on the subaerially marine deposits of last interglacial age, and biogenic methane formed by the bacterial breakdown of fossilized plant matter in the underlying deposits was released into the atmosphere from the exposed shelf. Due mainly to the poor drainage conditions, the exposed shelf was unlikely to support a dense vegetation cover causing a lowering of carbon storage through terrestrial plants. The role of greenhouse gases generated, trapped and escaping from the present-day continental shelves during the last interglacial cycle requires consideration in the estimation of global carbon flux. Reflection seismic profiling is useful as a method for mapping the present-day shelves to permit the identification of areas affected by acoustic turbidity. For the interval between the Holocene and the last interglacial, the geochemical characterization of sediment extracts is needed for the estimation of carbon flux and for obtaining information on past vegetation history. This necessitates the study of outer shelf sediments from water depths between about 130 and 200 m below the present-day sea level. The release of greenhouse gases from the exposed shelves during the last glacial period is suggested to provide a triggering mechanism for switching the earth into the present interglacial mode.

Barium increasing prior to opal during the last termination of glacial ages in the Okhotsk Sea sediments

Ba and Ti in a sediment core (10 m long) from the Okhotsk Sea, covering the last 120 kyrs, were measured. The authigenic Ba (Baex) contents were calculated and compared with the opal. The correlation coefficient between Baex and opal was quite small (r = 0.34), but it greatly grew larger (r = 0.90), if the Baex contents were multiplied by a simple function increasing with depth, except for two intervals. This may be due to the gradual change in the sedimentation environment during the glacial ages. One of the exceptional interval is found at 60–170 cm in depth, corresponding to 10–17 calendar kyr ago, the last termination period of glacial ages, where the Baex began to increase prior to opal. Since the calcium carbonate contents similarly increased prior to the opal increase, the Baex may be also related to calcareous organisms besides siliceous ones. The other is the last interglacial period around 120 kyr ago when the opal contents were high, but those of the Baex were not increased. This can be explained, if the Baex was reduced to sulfide and dissolved away in a strongly anoxic environment during the biologically productive period. During the glacial ages, the mass accumulation rate (MAR) of lithogenic Ti was about twice the amount of that during the interglacial ages. For opal, however, the contrast between the glacial and interglacial ages was more remarkable in its MAR than in its concentration in sediments, due to the larger variation in the bulk sedimentation rates.

Late Quaternary Upwelling Intensity and East Asian Monsoon Forcing in the South China Sea

Foraminifera from two cores off eastern Vietnam and the northwestern Philippines, where modern summer and winter monsoon-driven upwelling occurs in the South China Sea, respectively, were analyzed to evaluate the changes in paleoproductivity and upper water structure over the last 220,000 yr. We observed enhanced organic carbon flux and a shoaled thermocline when upwelling intensified off eastern Vietnam during interglacial ages and off the northwestern Philippines during glacial ages. This indicates that the East Asian summer monsoon increased while the winter monsoon decreased during interglacial ages. Particularly, the upwelling reached a maximum off eastern Vietnam during late marine isotopic stage (MIS) 5 and off the northwestern Philippines during MIS 2, implying that the summer monsoon decreased gradually since MIS 5 while the winter monsoon displayed an opposite trend. The variations in upwelling proxies exhibit a distinct cyclicity with frequencies near 41,000 yr and 23,000 yr off eastern Vietnam, in contrast to a strong frequency peak near 100,000 yr off the northwestern Philippines. We suggest that the East Asian summer monsoon has been forced by changes in solar insolation associated with precession and obliquity, while ice-volume forcing is probably a primary factor in determining the strength and timing of the East Asian winter monsoon but with less important insolation forcing.

Nelson Boulder Bank, New Zealand

Nelson Boulder Bank, a 13 km long barrier, separates Nelson Haven from Tasman Bay in the northern South Island. Its boulders, up to 1.2 m across, are of Cable Granodiorite, identical to rocks at Mackay Bluff at the northern end of the bank. Smaller clasts predominate in the top course and form recurved beach ridges, which mark successive ends of the bank, and are being replaced by longitudinal ridges. The clasts, which show a general decrease in size and increase in rounding away from MacKay Bluff, are moved southwest by longshore drift during northerly storm generated waves in the higher part of the tidal cycle. Smaller clasts tend to raft the larger boulders. The base course, of poorly sorted clasts in a soft, fine‐grained matrix, is protected by a layer of closely packed loose boulders. As the bank erodes and migrates shoreward, the smaller clasts are reworked and carried southwest, leaving large boulders seaward as a lag deposit. Radiocarbon dating indicates that the base course accumulated as the sea rose to its present level 6000 yr BR The top course spread along the base course during the past 6000 yr. Older boulder banks, and terrestrial gravel that accumulated during the Last Glaciation at the toe of Mackay Bluff, are an inferred major source of the boulders in the Boulder Bank. A submerged bank, of possible Last Interglacial age, off the end of the Boulder Bank may form the substrate to the northern part of the Boulder Bank.

Last Interglacial age of the Eva Forest Bed, Central Alaska, from thermoluminescence dating of bracketing loess

The Eva Forest Bed in the Yukon-Tanana Upland of east-central Alaska represents a frozen, buried, boreal forest. This bed consists of well-preserved peat lenses, sticks, roots, logs, as well as rooted and unrooted stumps of trees. Where preserved, the Eva Forest Bed is overlain by the Goldstream Formation and underlain by Gold Hill Loess. Almost all exposures have a prominent unconformity at the top of the Gold Hill Loess, even where the forest bed is not preserved. Attempts have been made over the last 50 yr to determine the age of this bed numerically. We report here details of thermoluminescence (TL) dating of 14 samples of loess from above and below this unconformity in the Fairbanks area. Together with knowledge about the climatic indicators from the Eva Forest Bed, these TL age estimates: (1) indicate that the most probable age of the Eva Forest Bed is ∼125 ka, the time of the warmest part of oxygen isotope stage 5; and (2) confirm stratigraphic inferences from tephra beds in the upper Gold Hill Loess that erosion has removed variable thicknesses of the original loess complex “just prior” to the development of the Eva Forest Bed.

Role of a Labile Terpene Compound in the Assessment of the Age of a Fossil Wood from Siena (Tuscany, Italy)

Summary Fossil samples of Pinus sylvestris found near Siena (Tuscany, Italy) in geological formations 2–3 million years old were chemically examined in order to solve the problem of the contrast between the age of geological formations and their good degree of preservation. Comparison with a living Pinus sylvestris was carried out on standard wood component analyses, cation exchange capacity and residual terpene content. The analyses of wood components were close to those of the reference pine, whilst the cation exchange capacity values showed remarkable changes. The increase of salt carboxyls suggested the hydrolysis of ester carboxyls originally present, whilst the reduction of total carboxyls revealed a partial loss of hemicelluloses. Both changes were attributed to the percolation of salt-bearing water through the wood, thus causing ester hydrolysis, carboxyl salification and hemicellulose solubilisation. Residual terpene analysis showed, for the first time in a terrestrial fossil, tetrahydroabietic acid which forms by disproportion of the abietic acid. The 14C dating assigned the fossil to an age of about 18,000 years and suggested a landslide of Wurmian interglacial age occurred inside the geological formations of 2–3 million years old. Transient terpene compounds, formed in incipient diagenesis, are proposed as tracers for the assessment of particular ranges of fossil age, as previously suggested by the analyses of both a Larix decidua 14,500 years old and a Picea abies 100,000 years

ESR dating stratigraphically well-constrained marine terraces along the Patagonian Atlantic coast (Argentina)

Abstract ESR dating of marine mollusc shells is an important tool in coastal geomorphology as well as in palaeosea-level and other research. Some severe problems, however, remain as far as the accuracy of the dating results are concerned. Case studies of Patagonian Middle and Younger Quaternary marine terraces help to illustrate the potential of an improved ESR dating technique. It can be demonstrated that a discrimination of Holocene, Last Interglacial, Penultimate Interglacial and “older” samples is possible. A chronostratigraphic separation of the well-known Last Interglacial substages 5a, 5c, and 5e is still missing, partly due to the misleading accuracy of ESR dating results. Consequently, it cannot be decided yet whether the morphologically well-conserved Last and Penultimate Interglacial age substages result from a relative sea-level fall (glacioeustatic and/or decreasing wind intensities) during the one and the same interglacial highstand shortly after the 5e or 7 transgression maximum or whether they were deposited during the much younger sea-level sub-highstands, e.g. 5c, 5a or 7c, or 7a.

Geochronology and palaeoenvironment of marine Quaternary deposits in Denmark: new evidence from northern Jutland

The degree of isoleucine epimerization in the benthic foraminiferal species Elphidium excavatum and Bulimina marginata have been measured in four boreholes, penetrating marine interglacial beds, from northern Jutland. The results of these analyses are compiled with results obtained from other sites in Denmark and the North Sea region, and four aminozones (AZs) have been erected. AZ1 (aIle/Ile < 0.05) include the Late Weichselian and the Holocene part of the record. AZ2 (0.08–0.12) includes samples of last interglacial age. AZ3 (0.14–0.16) includes samples from sites that have been previously correlated with the Holsteinian, and marine isotope stage 7 age for this zone is suggested. An age close to 400±100 ka is assigned to AZ4 (0.21–0.26). AZ4 is recorded in corings at Skagen and Nørre Lyngby, and includes the here defined Skagerrak Interglacial, which is tentatively correlated with marine isotope stage 11.The Skagerrak Interglacial sediments are characterized by boreal lusitanian benthic foraminiferal faunas evidencing strong input of Atlantic water to the North Sea. These faunas are replaced by assemblages indicating cooler conditions at least twice during this period. The sedimentation pattern in northern Jutland during this interglacial seems to be different from the sedimentation regimes in the same area at the classical Eemian sites and during the Holocene, which were characterized by large sediment input from the Jutland Current. This difference may be attributed to a change in the geometry of the sedimentary basin through the later part of the Quaternary, which is a result of repeated periods of intense erosion in the confluence area of the Norwegian Channel ice stream. A strong influx of Atlantic water to the North Sea during stage 11 has been suggested earlier, based on records from the Devil's Hole area. However, the correlation of this event to the classic biostratigraphic based schemes of northwest Europe is still problematic.

Ice-flow evolution of the Labrador Sector of the Laurentide Ice Sheet: a review, with new evidence from northern Quebec

Outcrops bearing stained, striated facets indicative of north–northeastward moving ice, truncated by unstained, striated facets indicative of various younger flows occur in the Caniapiscau area of north–central Quebec. This is the first report of differential staining of striated facets in the region. We propose that the staining occurred in an ice-free interval of probable interglacial age. This early ice flow probably occurred during ice retreat toward the Quebec highlands. Ice flow and glacial transport data from the southern Hudson Bay and James Bay basins indicate that the next major regional ice flow was toward the northwest and resulted from the expansion of an Early Wisconsinan glacier in the Quebec highlands. The northern part of this flow was diverted northwestward through Hudson Bay, and the southern part southwestward across James Bay, following a progressive counterclockwise rotation of flow. A zone of intersection (ZI) of two major glacier bedform systems, often referred to as the horseshoe-shaped Labrador Ice Divide, represents the head of a large northward convergent ice-flow system that extended to Ungava Bay and beyond. The Ungava flow propagated southward and captured the head of the opposing flow from an outflow centre located east of Caniaspiscau reservoir. We propose that this capture event correlates with the Gold Cove Advance in Ungava Bay and on Baffin Island at about 9900 14C yr BP. It is the largest advance of Quebec-Labrador ice yet proposed for the region. This correlation is based on the relative ice-flow chronology, accommodation of glacial lakes Naskaupi and McLean in the deglaciation sequence, the constraints placed on Last Glacial Maximum (LGM) ice configuration by the postglacial uplift pattern and events in the deep-sea record. Therefore, the Ungava ice-flow pattern is not a relict pre-Wisconsinan glacial landscape as recently proposed.

Penultimate Interglacial emerged reef around Kadavu Island, Southwest Pacific: Implications for late Quaternary island‐arc tectonics and sea‐level history

The Kadavu island group is a Pliocene‐Quaternary volcanic island arc in the Southwest Pacific, along which the last eruptions occurred during the late Quaternary. Recent investigations have focused on late Quaternary tectonic history with a view to illuminating regional plate interactions. The main island (Kadavu) is divisible into three structural blocks, the westernmost of which is the youngest and the least submergent. This block is surrounded by fragments of emerged reef limestone reaching 7.1 m above the modern reef surface (minimum emergence magnitude), cut by a prominent erosional (wave‐cut) bench at 2.6–3.4 m above the modern shore platform. Th/U dating of this limestone at the largest, highest outcrop—offshore Nagigia Island—revealed it to be of wholly Penultimate Interglacial age (207.2–223.2 ka). This result is explainable—plausibly not exclusively—by the following scenario. It is assumed that Penultimate Interglacial sea level reached a maximum of c. 10 m (relative to the present) around Kadavu, as it did around the Ryukyu islands of southern Japan, before falling. The western part of Kadavu was then uplifted 2 m, perhaps contemporaneously with the most recent phase of arc volcanism. An erosional bench was cut during an early Last Interglacial sea‐level maximum c. 136 000 yr ago when sea level reached c. 5 m above its present level. The reason there is no reef dating from this time is that reef upgrowth could not “keep up” with rapid sea‐level rise. Subsequent regression was followed by a slower rise of sea level (with which reef upgrowth did keep pace) to a second Last Interglacial maximum c. 120 000 yr ago, which reached some 2 m above present sea level. Subsequent subsidence of c. 2 m has carried this reef below present sea level, leaving the Penultimate Interglacial reef the only one emerged in western Kadavu today. The inferred 2 m uplift of western Kadavu between c. 200 and 130 000 yr ago may have been linked to the last phase of magmatic activity here, a time poorly constrained by available K‐Ar dates. Post‐120 ka subsidence may have been linked to a southward or southwestward shift in the axis of active volcanism associated with the nearby convergent plate boundary.

Pedosedimentary and climatic reconstruction of the last interglacial and early glacial loess–paleosol sequence in South Tadzhikistan

The thick loess–paleosol-sequences in Tadzhikistan, which indirectly record the environmental changes from the Upper Pliocene to the present-day, have been extensively described from a chronostratigraphical and archaeological point of view. The genesis of the soil-sedimentary complexes and their implications for palaeoenvironmental reconstruction in Tadzhikistan, however, have been considered only relatively recently [Bronger, A., Winter, R., Derevjanko, O., Aldag, S., 1993. Loess–paleosol sequences in Tadjikistan as a palaeoclimatic record of the Quaternary in Central Asia. Quaternary Proceedings 4, 69–81; Lomov, S.P., Tursina, T.V., Zhou, L.P., 1996. Magnetic susceptibility of soils: Micromorphology and possible reconstructions of climate. In: Soil micromorphology. Studies in Soil Diversity, Diagnostics, Dynamics, 10th International Working Meeting on Soil Micromorphology. Moscow, Russia, July 8–13, 1996, p. 145]. The pedocomplex of Last Interglacial and Early Glacial age (Oxygen Isotope Stage 5) in the Tagidjar and Darai Kalon sections near the town of Khovaling is represented by three major stages of soil formation. The soil characteristics have been micromorphologically analysed. The distinction between primary and secondary carbonates is of major importance to understand the soil forming processes. The relative distribution of needle fibre calcite (NFC), micritic infillings (M), hypocoatings (CHC), coarse calcitic grains (CCG) and calcified root cells (CRC) provides detailed insights into the environmental conditions prior, during and following pedogenesis. The abundance of coprolitic aggregates (CA) and pupal chambers gives a clear indication of the rate of biological activity which prevailed during the last two soil forming stages. Void pseudomorphs after gypsum crystals ( gypsum pseudomorphs) are frequently observed beneath the Cca horizons of the paleosols. Using the present-day climate and soilscape as a reference base, the obtained pedosedimentary events detected in the Tadzhikistan sections provide a detailed palaeoenvironmental record. Indeed, glacial and interglacial climates and soils respond to contemporaneous climatic schemes and soil forming processes, which are still active in the region today. The amount and the seasonal variability of precipitation, mostly, are at the origin of the variable soils formed during glacial and interglacial ages.

Facies architecture of a last interglacial barrier: a model for Quaternary barrier development from the Coorong to Mount Gambier Coastal Plain, southeastern Australia

The last interglacial Woakwine Range, a linear, barrier shoreline complex of temperate bioclastic carbonate origin, in the southeast of South Australia, occurs essentially uninterrupted over a distance of 300 km and up to 10 km inland from the present coastline. Mapping of the internal facies architecture of the barrier as revealed in McCourt's Cutting southeast of Robe, reveals the presence of transgressive and regressive facies associated with the last interglacial maximum (Oxygen Isotope Substage 5e), as well as an older aeolianite within the core of the barrier, correlated herein with Oxygen Isotope Stage 7. Amino acid racemisation and thermoluminescence dating indicate that volumetrically, the majority of the Woakwine Range is of last interglacial age. The bulk of the barrier structure comprises aeolian facies in the form of landward-migrating coastal dunes. The internal facies appear to record the culmination of the post-Stage 6 marine transgression at the onset of Substage 5e, and possibly the termination of Substage 5e based on the shallow seaward dip of the discontinuity between regressive littoral and sublittoral facies.

Radiocarbon dating and the reconstruction of late Quaternary sea-level changes in Hong Kong

Abstract Radiocarbon dating is used widely for the reconstruction of late Quaternary sea-level changes. In the present study, eight case studies in Hong Kong have been chosen to highlight the difficulty in obtaining reliable radiocarbon dates. Pre-Holocene radiocarbon dates exceeding about 8100 yr BP have been found to show a young age bias. A shell sample dated by two separate radiocarbon laboratories gave last interstadial ages differing by almost 9500 years while an oxygen-isotope stage 5e age was obtained using uranium-series dating. Other evidence including stratigraphy have shown that only the last interglacial age is acceptable. The young age bias is attributed mainly to the post-depositional introduction of ‘young’ carbon into the sample. For the reconstruction of sea-level changes, it is essential to select samples immediately above of the base of the Holocene transgressive unit in offshore boreholes and excavations to satisfy the criteria of rapid burial. These samples should preferably include mud, plant matter and shells to facilitate interpretation. Furthermore, as many samples as possible from a range of water depth down to about 130 m below the present sea level should be dated to reduce error introduced by counting statistics so the true signal of sea-level changes can be reflected.

Pleistocene palaeomeanders of the River Avon, Warwickshire

The river terrace record of the Warwickshire Avon contains a number of palaeomeander remnants. Sediments preserved within palaeomeanders at Cropthorne and Eckington underlie the No. 3 terrace of the Avon and have been shown to contain faunas of Ipswichian Interglacial age (Oxygen Isotope Substage (OIS) 5e). They are considered to represent deposition at that time in a meandering river. At Cropthorne the meander was ‘cut-off’ before the incision that preceeded the formation of the No. 2 terrace. A similar abandonment of a former meander is confirmed by clast lithological evidence from sediments around Broom near the Avon/Arrow confluence. Here the ‘cut-off’ is shown by molluscan evidence to have occurred after the establishment of cold climate conditions in the Devensian, and during the deposition of the sediments that underlie the No. 2 terrace. These adjustments of channel pattern are interpreted as response to change in discharge and sediment supply accompanying deterioration of climate at the end of the last interglacial. Palaeomeander remnants have been preserved by migration of the active valley floor away from them during the Devensian.

Bahamian coral reefs yield evidence of a brief sea-level lowstand during the last interglacial

The growth of large, bank-barrier coral reefs on the Bahamian islands of Great Inagua and San Salvador during the last interglacial was interrupted by at least one major cycle of sea regression and transgression. The fall of sea level resulted in the development of a wave-cut platform that abraded early Sangamon corals in parts of the Devil's Point reef on Great Inagua, and produced erosional breaks in the reefal sequences elsewhere in the Devil's Point reef and in the Cockburn Town reef on San Salvador. Minor red caliche and plant trace fossils formed on earlier interglacial reefal rocks during the low stand. The erosional surfaces subsequently were bored by sponges and bivalves, encrusted by serpulids, and recolonized by corals of younger interglacial age during the ensuing sea-level rise. These later reefal deposits form the base of a shallowing-upward sequence that developed during the rapid fall of sea level that marked the onset of Wisconsinan glacial conditions. Petrographic studies reveal a diagenetic sequence that supports this sea-level history. Preservation of pristine coralline aragonite, coupled with advances in U/Th age dating, allow these events in the history of the reefs to be placed in a precise chronology. We use these data to show that there was a time window of 1,500 years or less during which the regression/transgression cycle occurred and that rates of sea-level change must have been very rapid. We compare our results with the GRIP ice-core data, and show that the history of the Bahamian coral reefs indicates an episode of climate variability during the last interglacial greater than any reported in what is widely believed to be the more stable climate of the Holocene interglacial.

An interglacial macrofossil flora from Schulz Creek, north Westland, New Zealand

On a raised shoreline assumed to be of early Kaihinu Interglacial age (more than 100 kyr ago), in north Westland, well-preserved plant fossils are exposed in sediments in a road-cutting. They were probably deposited in a small freshwater lagoon behind a beach ridge, on a prograded shore. The fossils are robust (wood, coriaceous leaves, tough fruit, or seeds); almost certainly they represent only a proportion of the flora in Schulz Creek catchment at the time. The species composition (including Dacrydium cupressinum, Podocarpus hallii, Prumnopitys ferruginea, small conifers, Nothofagus spp., Metrosideros robusta, Elaeocarpus dentatus) suggests that the climate when the deposit was laid down was probably as mild as it is now. Most of the plant species of the fossil flora occur today in Schulz Creek catchment and the remainder live nearby.