Mid-late Holocene Research Articles

Long and short-time scale climatic variability in the last 5500 years in Africa according to modern and fossil diatoms from Lake Ossa (Western Cameroon)

The reconstruction of paleoenvironmental changes from diatoms in lake sediments is based on the usual assumption that, in each studied sample, the dominant species reflect the environment that prevailed during the time of deposition. If the environment changed significantly during the period of deposition (several years) one can expect a mixture of species having different or contradictory ecological affinities. In this paper we present analyses of diatoms in surface sediment samples collected in the Lake Ossa area (3°50′N, 9°36E) and fossil diatoms from a mid-late Holocene core retrieved in the deepest part of the lake. The Lake Ossa area alternates between a short dry season centered at around the northern winter and a long rainy season during the rest of the year entailing significant changes in water level and pH. Based on multivariate analyses, we will show here that mean annual water depth is the most significant variable explaining the distribution of diatoms in the entire Lake. However, seasonal changes of water level are poorly recorded by diatom assemblages, except in some flat areas on the borders of the lakes where a mixing between species with different affinities to water depth is likely due to seasonal changes in water level. Inferred water depth based on a quantitative transfer function reflected essentially secular to millennial changes in the studied core. The relationship between pH and diatoms is not statistically significant but seasonal to multi-annual pH variations mainly observed in the central parts of the lake are reflected by a mixing of acidophilous and alkaliphilous species. Hierarchical ascending cluster analysis (HAC) considered as the most efficient mean of describing diatom mixing shows that seasonal to multi-annual changes in pH are recorded both in the modern and fossil assemblages. According to the degree of mixing between diatoms with different pH affinities we conclude that short-term pH variability was weaker than today between 5200 and 2700 cal yr BP, stronger between 2700 and 2000 cal yr BP, weaker again between 2000 and 600 cal yr BP and similar to present from 400 cal yr BP onwards. Short-term changes were thus superimposed on secular to millennium trends recorded by modifications in the abundance of alkaliphilous diatoms. All these changes are interpreted as variations in precipitation according to a previous model showing that pH is strongly controlled by acidic meteoric water. Inferred water depth slightly changed over the last 5500 years showing weak variations of precipitation minus evaporation balance at secular to millennial time scales. These results will be used to refine previously published paleoclimatic interpretations, which explained changes in precipitation and P–E balance by modifications in the vertical structure of the atmosphere and subsequently by changes in cloud cover, convective or stratiform.

Holocene subsidence at the transition between strike-slip and subduction on the Pacific-Australian plate boundary, Marlborough Sounds, New Zealand

This paper provides the first solid evidence in support of a century-old hypothesis that the mountainous Marlborough Sounds region in central New Zealand is subsiding. More recent hypotheses suggest that this may be a result of southward migration of a slab of subducted Pacific Plate causing flexural downwarping of the overlying crust in the vicinity of the transition between subduction and strike-slip on the Pacific-Australian plate boundary. The proxy evidence for gradual Holocene subsidence comes from micropaleontological study of seven intertidal sediment cores from the inner Marlborough Sounds (at Havelock, Mahau Sound and Shakespeare Bay). Quantitative estimates (using Modern Analogue Technique) of former tidal elevations based on fossil foraminiferal faunas provide evidence of tectonic (not compaction-related) subsidence in all cores. Estimates of subsidence rates for individual cores vary within the range 0.2–2.4 m ka −1. The wide variation within subsidence rate estimates are related to a combination of the accuracy limits of radiocarbon dates, elevation estimates, and particularly our poor knowledge of the New Zealand Holocene sea-level curve. The most consistent subsidence rate at all three sites for the mid-late Holocene (last 6–7 ka) is ∼0.7–0.8 m ka −1. This rate is consistent with the average subsidence rate in the adjacent 4-km thick Wanganui sedimentary basin for the last 5 myr. Subsidence is inferred to have migrated southwards from the Wanganui Basin to impinge on the inner Marlborough Sounds in just the last 100–200 ka.

The evolution of soils of the taiga forest-steppe ecotone of the Baikal region during the Holocene

The territorial specific character of the main stages of Holocene pedogenesis is demonstrated. The study uncovers the characteristic features of bioclimatic evolution of chernozemic and texture-differentiated soils of the Mid-Holocene into organo-accumulative (soddy) soils typical of contemporary landscapes. For the Mid-Late Holocene five stages of soil formation have been identified, which are interrupted by an intensification of denudation-accumulative processes as a consequence of global coolings.

Beach Sediments from Northern South China Sea Suggest High and Oscillating Sea Levels During the Late Holocene

Understanding the history of the late Holocene sea level change is critical for predicting the potential effects of future sea level changes. The coral reef region of the Leizhou Peninsula, in the northern coast of the South China Sea, is an ideal site for studying the Holocene sea level history because of its tectonic stability and the possession of numerous prehistoric sea level indicators. The paleobeach sedimentary records from the Leizhou Peninsula indicated a higher-than-present sea level stand, from 1.7 to 1.2 Cal. ka BP (or 14C ages from 2.1 to 1.7 ka BP), which was punctuated by a short-term drop in the sea level at ∼1.5 Cal. ka BP. At 1.2 Cal. ka BP, the sea level was at least 128 cm higher than the present level. After that time, the sea level fell significantly resulting in the retreat of the coastline by ∼210 m and the formation of the modern beach-sand bank geomorphic system. Additional evidence from the coral reef records at this site suggested that similar to the climate change, the sea level also oscillated in the millennial-, centennial-, and interdecadal-scale cycles over the mid-late Holocene.

High-resolution windows into Holocene climate using proxy data from Belize corals (Central America)

Eleven fossil (Holocene) Montastraea coral samples from Belize barrier and atoll reef cores were analyzed geochemically. δ18O in fossil Montastraea cores suggest warmer and/or wetter conditions in the early–mid-Holocene and the modern age as compared to the mid–late-Holocene, ca. 5000–1,000 years before present (BP). Both δ18O and δ13C data in fossil coral cores exhibit the highest amplitudes from ca. 7,000–4,000 years BP, and indicate a higher climate variability in the early–mid-Holocene. Due to the maximum length of 20 years of individual samples, spectral analyses of fossil time series are beyond the methodological scope of this study. Oxygen and carbon isotope (δ18O and δ13C) time series from two modern (AD 1895–2005) Montastraea corals collected offshore of Belize are used for comparison. The δ18O and δ13C from these time series may be used as proxies for sea surface temperature (SST), precipitation, cloud cover, and the impact of anthropogenic production of CO2, respectively. δ18O variation indicates an increase in SST over the 20th century in the study area.

Shelf sedimentation on a tectonically active margin: A modern sediment budget for Poverty continental shelf, New Zealand

The combination of high sediment yields and the prevalence of tectonically controlled accommodation on collision margins such as that adjacent to the Waipaoa River, NZ, create the potential for these areas to contain high-resolution records of natural and anthropogenic signals. This study describes modern (100-yr) sedimentation patterns off the Waipaoa and quantifies a sediment budget for the continental shelf, which is compared to long-term Holocene trends. 210Pb and 239,240Pu geochronologies reveal three main shelf depocenters. Two of these depocenters are located in subsiding synclinal basins on the mid-shelf, landward of the actively deforming Ariel and Lachlan anticlines. The depocenters exhibit accumulation rates ranging from 0.75 to 1.5 cm yr − 1 and display both steady-state and non-steady-state 210Pb activity profiles. Textural characteristics of the non-steady-state cores indicate the possible preservation of flood event layers. The third depocenter is located near the shelf break and has accumulation rates as high as 1.0 cm yr − 1 . The inner shelf and central mid-shelf are characterized by low, uniform 210Pb activity profiles and low accumulation rates, indicating that sediment is bypassing the inner shelf region and being deposited on the mid- to outer shelf. The modern sedimentation patterns seen in this study are similar to those for the Holocene, suggesting that regional tectonics are the major influence on Poverty shelf sedimentation. A modern, bulk sediment budget estimates that 3.6 ± 0.9 × 10 6 t yr − 1 of sediments remains on the shelf, amounting to only ~ 25% of the 15 Mt of sediments discharged from the river per year. This indicates massive export of sediments from the study area to the adjacent slope or along the shelf. In contrast, studies of the Mid-Late Holocene sediment budget in the same area indicate that the sediment input and shelf trapping have been roughly in balance. When compared with the modern budget, this suggests an extraordinarily rapid shift from shelf trapping to shelf bypassing, most likely driven by increasing sediment discharge in response to deforestation.

Reconstructing the development of the geosystems of the Primorsky Range during the latter half of the Holocene

We examine the sequence of changes in the structure of the geosystems of the Primorsky Range (Baikal region) for the last 6000 years, based on a continuous recording of fluctuations of the vegetation reconstructed from spore-pollen complexes of a high peat bog. We determined the chronological timeframe of paleogeographical events. The study showed that there occurred a radical structure transformation of the geosystems in the mid-late Holocene, along with a recurrence of similar landscape transformations caused by the instability of natural conditions.

Geomorphic evidence for mid–late Holocene higher sea level from southeastern Australia

An elevated sheltered pocket beach sequence at Batemans Bay, NSW, Australia, composed of shelly fine- to medium-grained sand provides geomorphic evidence of higher than present sea level during the mid–late Holocene. The sequence is composed of a sand facies with variable amounts of shell and contains a number of well-defined dipping reflectors identified in ground penetrating radar (GPR) profiles indicative of a small prograded beach system. This beach succession is overlain by storm or tsunami deposits. The beach deposit accumulated between 2500 and 5000 cal BP under relatively high energy conditions within a more open immature estuary during a period of higher sea level. Both deposits have been preserved by a low energy mangrove facies that accumulated after the recent fall in sea level cut off ocean wave activity from the area approximately 2000–2500 cal BP. This beach sequence provides new evidence for a period of higher sea level 1–1.5 m higher than present that lasted until at least c. 2000–2500 cal BP and adds complementary geomorphic evidence for the mid to late Holocene sea-level highstand previously identified along other parts of the southeast Australian coast using other methods.

Climate drivers for peatland palaeoclimate records

Reconstruction of hydroclimate variability is an important part of understanding natural climate change on decadal to millennial timescales. Peatland records reconstruct 'bog surface wetness’ (BSW) changes, but it is unclear whether it is a relative dominance of precipitation or temperature that has driven these variations over Holocene timescales. Previously, correlations with instrumental climate data implied that precipitation is the dominant control. However, a recent chironomid inferred July temperature record suggested temperature changes were synchronous with BSW over the mid-late Holocene. This paper provides new analyses of these data to test competing hypotheses of climate controls on bog surface wetness and discusses some of the distal drivers of large-scale spatial patterns of BSW change. Using statistically based estimates of uncertainty in chronologies and proxy records, we show a correlation between Holocene summer temperature and BSW is plausible, but that chronologies are insufficiently precise to demonstrate this conclusively. Simulated summer moisture deficit changes for the last 6000 years forced by temperature alone are relatively small compared with observations over the 20th century. Instrumental records show that summer moisture deficit provides the best explanatory variable for measured water table changes and is more strongly correlated with precipitation than with temperature in both Estonia and the UK. We conclude that BSW is driven primarily by precipitation, reinforced by temperature, which is negatively correlated with precipitation and therefore usually forces summer moisture deficit in the same direction. In western Europe, BSW records are likely to be forced by changes in the strength and location of westerlies, linked to large-scale North Atlantic ocean and atmospheric circulation.

Holocene sediment dynamics in an upland temperate lake catchment: climatic and land-use impacts in the English Lake District

Accelerated erosion and transport of fine sediment from upland temperate catchments can reflect increased erosivity and/or erodibility, due in turn to climatic and/or human forcing. Identification of sediment fluxes and sources over Holocene timescales can both enable understanding of the relative impacts of these forcings and provide perspective on recent sediment fluxes. Here we present a ~ 5500 yr record of sediment fluxes and sources from Lake Bassenthwaite in the English Lake District, utilizing magnetic measurements and fuzzy clustering, coupled with independent pollen and archaeological records, to identify the timing and impact of catchment disturbance. This record shows that recent sediment flux increases (ie, within the last 150 years) are unprecedented in scale throughout the mid—late Holocene and appear to be in response to specific human changes occurring within the catchment. Earlier episodes of human activity, from the mid Holocene onwards, show no link with increased lake sediment fluxes, indicating either limited catchment impact and/or `buffering' through within-catchment sediment storage. Increasingly intensive land use and reduction of sediment storage through revetment construction on a key inflow, Newlands Beck, have resulted in 3 × increases in lake sediment flux. These data may be significant for other upland temperate areas, as increasing land-use pressures and reduced sediment storage capacity may not only increase contemporary sediment flux, but increase sensitivity to predicted increases in rainfall and storminess as a result of global climate change.

Stable isotopes of a subfossil Tamarix tree from the Dead Sea region, Israel, and their implications for the Intermediate Bronze Age environmental crisis

Trees growing on the Mt. Sedom salt diapir, at the southern Dead Sea shore, were swept by runoff into salt caves and subsequently deposited therein, sheltered from surface weathering. A subfossil Tamarix tree trunk, found in a remote section of Sedom Cave is radiocarbon dated to between ∼ 2265 and 1930 BCE. It was sampled in 109 points across the tree rings for carbon and nitrogen isotopes. The Sedom Tamarix demonstrates a few hundred years of 13C and 15N isotopic enrichment, culminating in extremely high δ 13C and δ 15N values. Calibration using modern Tamarix stable isotopes in various climatic settings in Israel shows direct relationship between isotopic enrichment and climate deterioration, particularly rainfall decrease. The subfossil Tamarix probably reflects an environmental crisis during the Intermediate Bronze Age, which subsequently killed the tree ∼ 1930 BCE. This period coincides with the largest historic fall of the Dead Sea level, as well as the demise of the large regional urban center of the 3rd millennium BCE. The environmental crisis may thus explain the archaeological evidence of a shift from urban to pastoral culture during the Intermediate Bronze Age. This was apparently the most severe long-term historical drought that affected the region in the mid-late Holocene.

Modelling late Quaternary changes in plant distribution, vegetation and climate using pollen data from Georgia, Caucasus

AbstractAim To use pollen data, numerical analysis and modelling to reconstruct late Quaternary vegetation and climate in a complex, mountainous environment.Location Georgia (Caucasus region).Methods Pollen data were assembled from various sources and used to map: (1) changing frequencies of individual taxa; (2) vegetation changes; and (3) reconstructed climatic parameters for the past 14,000 years. Numerical analyses were performed using two‐way indicator species analysis (twinspan), detrended correspondence analysis (DCA), the modern analogue technique (MAT) and weighted averaging (WA).Results Mapping of pollen taxa showed that Chenopodiaceae, Artemisia and Ephedra were most abundant in the study area during the late‐glacial. Betula and Corylus expanded during the early Holocene, yielding to Abies, Carpinus, Fagus, Quercus and Castanea. Picea, Pinus, Juglans and Ostrya‐type expanded during the late Holocene. Mixed forests grew in the moist, Black Sea refugium throughout the late Quaternary. Elsewhere in Georgia, the Pleistocene–Holocene transition is recorded as a shift from desert‐steppes to oak‐xerophyte communities and mixed forests. This kind of vegetation remained relatively stable until the mid–late Holocene, when coniferous forests and mountain grasslands advanced. DCA showed that rainfall was most strongly correlated with pollen composition in the study area (r2 = 0.55). No temperature signal was detected. A weighted‐averaging transfer function linking pollen percentages to annual precipitation was selected over a MAT model as it performed better when applied to a validation data set. Rainfall reconstructions indicate widespread aridity at the terminal Pleistocene, followed by a gradual increase in precipitation, peaking during the mid Holocene (7000–4000 cal. yr bp) and generally decreasing thereafter.Main conclusions On a regional scale, the results confirm those from previous studies of palaeovegetation and palaeoclimate in Western Asia. On a local scale, reconstructions from individual sites often diverge from the regional trend because of edaphic changes, ecological succession, human impacts and other disturbances. Some of these factors are probably responsible for the increasing heterogeneity of Georgia’s vegetation in the latter half of the Holocene.

Palynological records of mangrove degradation around Chilka Lake, Orissa, India

The pear shaped Chilka Lake lying along the eastern coast of Orissa State, is one of the ecological and socioeconomical important wetlands of India. This open lagoon is identified as a nationally important and internationally renowned ecosystem, which harbours a range of marine, brackish and fresh water biodiversity. Palynological syntheses based on the results of investigated mid-late Holocene profiles (Balugaon, Rambha, Nalabana, Dangmal, Solari, Chandrapur, Geokhala, Bhowania) are compared with the upper part of core CHI-9 encompassing period of 13,000 years. It has been observed from the pollen record that tropical dense mangrove forest thriving luxuriantly during early Holocene has decreased considerably with the passage of time.
 The present mangrove ecosystem, though more restricted, is fairly stable with maintenance of conserved mangrove forests in protected prograding bays in Mahanadi delta and in estuaries kept open by adequate river flow. However, siltation, eutrophication and industrial development are major threatening factors affecting the sensitivity of lake resulting in shrinkage and total disappearance of surrounding vegetation. It has been indicated that certain metals, such as Co, Cr, Cu, Ni, V, Zn As, Pb, Cd are responsible for the environmental stress of the ecosystem which are continuously incorporated by the use of fertilizers and pesticides in agriculture. There should be an appeal and educational effort to stop the destruction and fragmentation of mangroves. The planned eco-friendly rehabilitation of mangroves, along with harmonious urban development and industrialization is required in order to restore the past glory of Chilka Lake.

Instability of seawater pH in the South China Sea during the mid-late Holocene: Evidence from boron isotopic composition of corals

We used positive thermal ionization mass spectrometry (PTIMS) to generate high precision δ 11B records in Porites corals of the mid-late Holocene from the South China Sea (SCS). The δ 11B values of the Holocene corals vary significantly, ranging from 22.2‰ to 25.5‰. The paleo-pH records of the SCS, reconstructed from the δ 11B data, were not stable as previously thought but show a gradual increase from the Holocene thermal optimal and a sharp decrease to modern values. The latter is likely caused by the large amount of anthropogenic CO 2 emissions since the Industrial Revolution but variations of atmospheric pCO 2 cannot explain the pH change of the SCS before the Industrial Revolution. We suggest that variations of monsoon intensity during the mid-late Holocene may have driven the sea surface pH increase from the mid to late Holocene. Results of this study indicate that the impact of anthropogenic atmospheric CO 2 emissions may have reversed the natural pH trend in the SCS since the mid-Holocene. Such ocean pH records in the current interglacial period can help us better understand the physical and biological controls on ocean pH and possibly predict the long-term impact of climate change on future ocean acidification.

Holocene mangrove and coastal environmental changes in the western Ganga–Brahmaputra Delta, India

A 50 m-long radiocarbon dated core was studied through sediment and pollen analysis to reconstruct the Holocene mangrove and environmental changes at a coastal site Pakhiralaya in the Sundarban Biosphere Reserve in the western Ganga–Brahmaputra Delta, India. This biosphere reserve harbours a diverse mangrove ecosystem and supports a large number of people living in the area. Pollen and stratigraphic data indicate the existence of a brackish water estuarine mangrove swamp forest in this area during the last 9880 cal yr b.p. The development of the mangrove forest is not shown continuously in the Holocene record. Rapid transgression of the sea (9240 cal yr b.p.) halted the development of the mangrove. After about 8420 cal yr b.p. mangrove recolonised the area and persisted until 7560 cal yr b.p. as a result of a balance between the sedimentation and sea level fluctuation. The mangrove disappeared again from the site until 4800 cal yr b.p. because of a high sedimentation rate and possible delta progradation with loss of habitats. The reappearance of mangrove at the study site occurred with a return of a brackish water estuarine environment and the site then gradually became supra tidal during the mid-late Holocene. The continuity of the mangrove development and dynamics was interrupted by the fluctuating sea levels. Climatic fluctuations were viewed as an indirect factor influencing the mangrove ecosystem.

Reorganization of the upper ocean circulation in the mid-Holocene in the northeastern AtlanticThis article is one of a series of papers published in this Special Issue on the theme Polar Climate Stability Network.GEOTOP Publication 2009-0002.

A micropaleontological investigation was conducted on two sediment cores from the Reykjanes Ridge (RR; core LO09-14; 59°12.30′N, 31°05.94′W) and the Faroe–Shetland Channel (FSC; core HM03-133-25; 60°06.55′N, 06°04.18′W) to document hydrographical changes of the North Atlantic Current (NAC) during the Holocene. Dinocyst and coccolith assemblages were analyzed, and quantitative reconstructions of sea surface temperatures (SSTs) and sea surface salinities (SSSs) were conducted based on dinocyst assemblages. Both proxies suggest a major reorganization of surface circulation patterns in the northeastern North Atlantic between 7 and 5.4 ka BP. At both sites, SSSs before 6.5–7 ka BP were lower than during the mid-late Holocene, suggesting dispersal of meltwater through the NAC. Long term trends of SSTs, however, show higher than present summer SSTs on the RR from 9.3 to ∼6 ka BP, and lower than present SSTs in the FSC until ca. 5.4 ka BP. The contrasted SST trends at the two sites suggest that decreasing summer insolation was not the only forcing behind hydrographical changes in the region. Decoupling of the NAC and the Slope Current (SC), which both influence the FSC, is proposed as a possible mechanism. We hypothesize that a strong NAC during the early to middle Holocene resulted in a SST increase on the RR and decrease in the FSC. Inversely, a weaker NAC after 5–6 ka BP, leading to decreased SSTs on the RR, would have enhanced the relative contribution of the warmer, saltier SC in the FSC, thus resulting in a regional SST and SSS increase.

Intentional or incidental thermal modification? Analysing site occupation via burned bone

Although there has been extensive experimental research on the thermal modification of bone, the results have rarely been applied to interpret zooarchaeological assemblages. The faunal assemblage from Wanderer's Cave, Australia was analysed to investigate the origins, timing and context in which faunal specimens became burned during the mid–late Holocene occupation of the site. Statistical analyses of uniformity of burning, burning over fracture surfaces and epiphyses, frequency of carbonisation by prey taxa, and thermal modification of canid modified specimens indicate that the majority of faunal specimens were unintentionally modified when on the surface of the deposit or while buried in sediment when fires were lit at subsequent site occupation events. Thermal modification at the site does not reflect intentional cooking activities. Significant preservation biases were identified from the lower acidic levels of the site, preventing knowledge of the early fire history at Wanderer's Cave.

Subtropical sea-level history from coral microatolls in the Southern Cook Islands, since 300 AD

Relative sea-level (RSL) history is reconstructed for the Southern Cook Islands since 300 AD using Porites sp. coral microatolls. The upper surface or height of living coral of the modern microatolls on Rarotonga was rigorously determined by 400 laser survey measurements to be constrained by the sea-level − 0.36 m (below Mean Sea Level) with a standard deviation of ± 0.008 m, that is equivalent to midway between Mean Low Water Neaps and Mean Low Water Springs tidal datums. Fossil microatoll history on the fringing reefs is fragmentary due to multi-decadal to centennial windows of microatoll growth, cyclone destruction, and preservation through coastal progradation. The mid-late Holocene highstand ceased prior to 500 BC and RSL fell from + 1.3 ± 0.1 m to 0.45 ± 0.15 m by 1000 AD at a rate of − 0.5 mm/yr. The RSL minimum occurred during the late 1700s to 1800s AD at − 0.2 m below present, before rising during the 1900s. During the past 500 yr RSL fluctuated, including an abrupt fall at ~ 1750 AD following a sustained multi-decadal high anomaly. Similarly, low RSL anomalies and slow coral growth rates during the 950 to 1000 AD period are indicative of Pacific Basin-wide climate variability and are consistent with extreme La Niña-like climate anomalies previously reported around the Pacific basin. The fall in RSL during the first millennium AD crossed-over tidal thresholds for rapid coastal progradation, when ambient Mean High Water Neaps and Mean High Water Springs fell below the low tide level of the mid-late Holocene high stand. This coastal response is inversely analogous to the projected response to sea-level rise during the latter part of the modern century.

Two decadally resolved records from north‐west European peat bogs show rapid climate changes associated with solar variability during the mid–late Holocene

AbstractTwo 14C accelerator mass spectrometry (AMS) wiggle‐match dated peat sequences from Denmark and northern England record changes in mire surface wetness reconstructed using plant macrofossil and testate amoebae analyses. A number of significant mid–late Holocene climatic deteriorations (wet shifts) associated with declines in solar activity were recorded (at ca. 2150 cal. yr BC, 740 cal. yr BC, cal. yr AD 930, cal. yr AD 1020, cal. yr AD 1280–1300, cal. yr AD 1640 and cal. yr AD 1790–1830). The wet shifts identified from ca. cal. yr AD 930 are concurrent with or lag decreases in solar activity by 10–50 years. These changes are replicated by previous records from these and other sites in the region and the new records provide improved precision for the ages of these changes. The rapidly accumulating (up to 2–3 yr cm−1, ∼1310 yr old, 34 14C dates) Danish profile offers an unprecedented high‐resolution record of climate change from a peat bog, and has effectively recorded a number of significant but short‐lived climate change events since ca. cal. yr AD 690. The longer time intervals between samples and the greater length of time resolved by each sample in the British site due to slower peat accumulation rates (up to 11 yr cm−1, ∼5250 yr old, 42 14C dates) acted as a natural smoothing filter preventing the clear registration of some of the rapid climate change events. Not all the significant rises in water table registered in the peat bog archives of the British and Danish sites have been caused by solar forcing, and may be the result of other processes such as changes in other external forcing factors, the internal variability of the climate system or raised bog ecosystem. Copyright © 2008 John Wiley & Sons, Ltd.

Indo-Pacific Migration and Colonization—Introduction

In this Introduction we comment on issues raised by the present collection of papers as they appear relevant in thinking about the settlement of the Indo-Pacific from the Pleistocene to the late Holocene. Successful maritime migration across this vast region was obviously related to voyaging technology and colonizing behaviors. Here we critique earlier models that indicate simple unidirectional expansion and posit farming, or indeed any other single driver, for maritime expansion in the mid–late Holocene. It now appears that the development of interaction spheres in Wallacea, and perhaps connections with New Guinea, have contributed significantly to late Holocene societies in ISEA and Island Melanesia. Even in Remote Oceania where long-term colonizing success was dependent on a transported tropical horticultural complex, initial settlement strategies are likely to have been highly varied and to have had variable success. Nor is migration restricted to the founding events of island settlement; rather, it continued as a significant component of the formation and re-formation of island cultures up to the historical era and, of course, within the present day. Like the authors represented here we suggest that if we wish to make progress in understanding the motives, sources, mechanisms and results of colonizing migration, there will be greatest reward in exploring the complexity and variability that lie behind it.