Papers by Alex Chepstow-Lusty
High-resolution records of Upper Pliocene Discoaster abundances were analysed from two ODP (Ocean... more High-resolution records of Upper Pliocene Discoaster abundances were analysed from two ODP (Ocean Drilling Program) Sites, Site 677 (I 0 N, 84°W) and Site 806 (0°N, 159°E). Both sites are in the equatorial Pacific Ocean, but almost 13,000 km apart. A high-resolution oxygen isotope stratigraphy from Site 677 has formed the basis of a revised, orbitally-tuned timescale. This timescale was extrapolated to Site 806 using biostratigraphic datums. The Discoaster brouweri records at bOth sites prior to its extinction at 1.95 Ma (isotope Stage 72) document a dramatic reduction in abundance between 2.15 and 2.12 Ma (isotope Stages 82 and 80, respectively). The Discoaster triradiatus acme (2.15-1.95Ma) coincides with this interval of low Discoaster abundance but is still clearly discernible. Site 677 in the eastern Pacific is affected by the cold Peru Current. It is suggested that the advection of cooler water intensified during glacial isotope Stage 82, causing increased upwelling and lower sea-surface temperatures, which suppressed Discoaster production. Site 806, in the western Pacific is affected by divergence related to the equatorial currents, rather than by a cool boundary current system, so surface-water temperatures are relatively stable on a glacial-interglacial scale. The decline in Discoaster abundance in the western equatorial ocean, during isotope Stage 80, is, therefore, more likely to be attributable to the position of equatorial divergence and corresponding changes in the thermocline and nutricline. The decline in abundance patterns observed in the two equatorial Pacific sites are also evident in records from the equatorial Indian and Atlantic Oceans, although the reduction in Discoaster abundances in these two regions are less extreme.
Palaeogeography, Palaeoclimatology, Palaeoecology, Mar 1, 2008
The Open University's repository of research publications and other research outputs Glacial-Inte... more The Open University's repository of research publications and other research outputs Glacial-Interglacial changes in moisture balance and the impact on vegetation in the southern hemisphere tropical Andes (Bolivia/Peru)
Journal of Nannoplankton Research, 1995
High-resolution records of Upper Pliocene Discoaster abundances were analysed from two ODP (Ocean... more High-resolution records of Upper Pliocene Discoaster abundances were analysed from two ODP (Ocean Drilling Program) Sites, Site 677 (I 0 N, 84°W) and Site 806 (0°N, 159°E). Both sites are in the equatorial Pacific Ocean, but almost 13,000 km apart. A high-resolution oxygen isotope stratigraphy from Site 677 has formed the basis of a revised, orbitally-tuned timescale. This timescale was extrapolated to Site 806 using biostratigraphic datums. The Discoaster brouweri records at bOth sites prior to its extinction at 1.95 Ma (isotope Stage 72) document a dramatic reduction in abundance between 2.15 and 2.12 Ma (isotope Stages 82 and 80, respectively). The Discoaster triradiatus acme (2.15-1.95Ma) coincides with this interval of low Discoaster abundance but is still clearly discernible. Site 677 in the eastern Pacific is affected by the cold Peru Current. It is suggested that the advection of cooler water intensified during glacial isotope Stage 82, causing increased upwelling and lower sea-surface temperatures, which suppressed Discoaster production. Site 806, in the western Pacific is affected by divergence related to the equatorial currents, rather than by a cool boundary current system, so surface-water temperatures are relatively stable on a glacial-interglacial scale. The decline in Discoaster abundance in the western equatorial ocean, during isotope Stage 80, is, therefore, more likely to be attributable to the position of equatorial divergence and corresponding changes in the thermocline and nutricline. The decline in abundance patterns observed in the two equatorial Pacific sites are also evident in records from the equatorial Indian and Atlantic Oceans, although the reduction in Discoaster abundances in these two regions are less extreme.
Journal of Coastal Research, Oct 23, 1999
On samples recovered from trench profiles on Neuwerk, a little island on the German North Sea coa... more On samples recovered from trench profiles on Neuwerk, a little island on the German North Sea coast. palynology. heavy metal and cesium analyses were carr ied out in order to reveal the historical development of the island. All thr ee analytical approaches yielded good results with regard to the relatively recent developments. The cesium determinations suggest that sedimentatio n during most of the last fifty years has been in the order of 2.1 rn rn/yr , but under the influence of increased storm surge heights and frequencies has recently accelerated to about 6.0-7 .5 mm/yr. The earlier history of the island is revealed by stratigra phical investigations. Aclear sequence of vegetationsuccession is recorded, which is followed by a series of plant communities maintai ned by ani mal grazing.
Journal of Micropalaeontology, Mar 1, 1991
Abundance variations of six Pliocene species of the nannofossil genus Discoaster were analyzed ov... more Abundance variations of six Pliocene species of the nannofossil genus Discoaster were analyzed over the time interval 1.89-2.95 Ma at five sites in the North Atlantic; DSDP 552 (56"N), DSDP 607 (41"N), ODP 659 (18"N), ODP 658 (20"N) and ODP 662 (1"s). Individual species are compared between the five sites as a percentage of the total Discoaster assemblage, using age models based mainly on Discoaster datums (3 control points used at each site). The sampling interval is approximately 3 kyrs. Discoaster brouweri, the only species covering the complete time interval became a less significant component of the assemblages with increasing latitude during the interval prior to 2.3 Ma. Discoaster triradiatus shows a distinct abundance acme at all sites between 1.89-2.7 Ma. Discoaster surculus increased in relative abundance with higher latitudes and upwelling conditions (ODP Site 658). Discoasterpentarudiatus is an important component of the assemblages at all sites, but displays an inverse abundance relationship with D. surculus as a function of increasing latitude and upwelling conditions. Discoaster tamalis and Discoaster asymmetricus are reduced at low latitudes and in upwelling conditions and increase relative to D. hrouweri at higher latitudes, where there is strong evidence for taxonomic affinity.
Biological Journal of The Linnean Society, Sep 1, 1995
The vascular plant flora of the Pitcairn Islands, south-central Pacific Ocean, is described based... more The vascular plant flora of the Pitcairn Islands, south-central Pacific Ocean, is described based on extensive new collections made in 1991 and previously published records. Two vascular plants occur on Ducie Atoll; one (Pemphis acidula) is a new record. Sixty-three native vascular plants occur on Henderson, of which nine are endemic; Canavalia rosea, Operculina turpethum, Psilotum nudum and Solanum americanum are new records for the island. Oeno Atoll has 16 native vascular plants; the single endemic (Bidens hendersonensis var. oenoensis) was not found in 1991 despite careful searches. Triumfetta procumbens was new for Oeno. Sixty-six native vascular plants have now been recorded from Pitcairn Island, there are two endemic ferns and seven endemic angiosperms in this number. A number of non-native taxa were new to Pitcairn. Some of the previously described taxa could not be found on Pitcairn, probably because they are very rare and only a small amount of time was spent collecting on Pitcairn. Many of the Pitcairn taxa are threatened by the spread of introduced species, especially Syzygium jambos.
Palaeogeography, Palaeoclimatology, Palaeoecology, Nov 1, 1997
High-resolution records (2 7 kyr) of Upper Pliocene Discoaster abundances obtained from six ODP/D... more High-resolution records (2 7 kyr) of Upper Pliocene Discoaster abundances obtained from six ODP/DSDP sites are assessed independently using oxygen isotope stratigraphy. Four Atlantic Ocean sites (DSDP Sites 552 and 607, and ODP Sites 659 and 662) comprise a transect from 56°N to I°S and provide a record of latitudinal variations in Diseoaster biogeography. Low-latitude sites in the Atlantic (ODP Site 662), Pacific (ODP Site 677), and Indian (ODP Site 709) oceans provide additional information about variability in Discoaster abundance patterns within the equatorial region. A common chronology, based on the astronomical time scale developed for ODP Site 677, has been established for all the sites. By integrating oxygen isotope data and Discoaster abundance records at each site we are able to independently evaluate the temporal and spatial distribution of D. brouweri and D. triradiatus in the 500 kyr prior to the extinction of the discoasters near the base of the Olduvai subchron. Major decreases in abundance are evident during some of the more intense late Pliocene glacial events. In particular, glacial isotope stages 82, 96, 98 and 100 are associated with distinct abundance minima. At these times, large-scale changes in surface hydrographic conditions appear to have suppressed Diseoaster numbers on a global scale. The increase in abundance of D. triradiatus, which precedes the extinction of the discoasters by around 200 kyr, may also be related to the intensification of environmental pressures that accompanied the build-up of Northern Hemisphere ice sheets during the late Pliocene. In spite of contrasting geographic and oceanographic settings, the various D. brouweri and D. triradiatus records are remarkably similar. This demonstrates that the acme and extinction events are excellent biostratigraphic datums. The simultaneous extinction of D. brouweri and D. triradiatus at 1.95 Ma were synchronous events at both a regional scale within the Atlantic, and on a global scale between the three major oceans. However, the start of the D. triradiatus acme appears to have been diachronous, occurring some 40 kyr earlier in the Atlantic than in the Indo-Pacific, and hence the stratigraphic usefulness of this datum is regional rather than global.
Proceedings of the Ocean Drilling Program, Dec 1, 1989
Abundance variations of six Pliocene species of discoasters have been analyzed over the time inte... more Abundance variations of six Pliocene species of discoasters have been analyzed over the time interval from 1.89 to 2.95 Ma at five contrasting sites in the North Atlantic: Deep Sea Drilling Project Sites 552 (56°N) and 607 (41°N) and Ocean Drilling Program 658 (20°N), 659 (18°N), and 662 (1°S). A sampling interval equivalent to approximately 3 k.y. was used. Total Discoaster abundance showed a reduction with increasing latitude and from the effects of upwelling. This phenomenon is most obvious in Discoaster brouweri, the only species that survived over the entire time interval studied. Prior to 2.38 Ma, Discoaster pentaradiatus and Discoaster surculus are important components of the Discoaster assemblage: Discoaster pentaradiatus increases slightly with latitude up to 41°N, and its abundance relative to D. brouweri increases up to 56°N; D. surculus increases in abundance with latitude and with upwelling conditions relative to both D. brouweri and D. pentaradiatus and is dominant to the latter species at upwelling Site 658 and at the highest latitude sites. Discoaster asymmetricus and Discoaster tamalis appear to increase in abundance with latitude relative to D. brouweri. Many of the abundance changes observed appear to be connected with the initiation of glaciation in the North Atlantic at 2.4 Ma. The long-term trend of decreasing Discoaster abundance probably reflects the fall of sea-surface temperatures. This trend of cooling is overprinted by short-term variations that are probably associated with orbital forcing. Evidence for the astronomical elements of eccentricity and obliquity periodicities were found at all sites; however, only at Sites 607, 659, and 662 were precessional periodicities detected. Furthermore, only at Site 659 was precession found to be dominant to obliquity. Abundance peaks of individual species were found to cross-correlate between sites. The distinct abundance fluctuations observed especially in the tropics suggest that temperature is not the only factor responsible for this variation. This study reveals for the first time the importance of productivity pressure on the suppression of Discoaster abundance.
Climate of The Past, Jul 22, 2009
The rapid expansion of the Inca from the Cuzco area of highland Peru (ca. AD 1400-1532) produced ... more The rapid expansion of the Inca from the Cuzco area of highland Peru (ca. AD 1400-1532) produced the largest empire in the New World. Although this meteoric growth may in part be due to the adoption of innovative societal strategies, supported by a large labour force and a standing army, we argue that it would not have been possible without increased crop productivity, which was linked to more favourable climatic conditions. Here we present a multi-proxy, high-resolution 1200-year lake sediment record from Marcacocha, located 12 km north of Ollantaytambo, in the heartland of the Inca Empire. This record reveals a period of sustained aridity that began from AD 880, followed by increased warming from AD 1100 that lasted beyond the arrival of the Spanish in AD 1532. These increasingly warmer conditions would have allowed the Inca and their immediate predecessors the opportunity to exploit higher altitudes (post-AD 1150) by constructing agricultural terraces that employed glacial-fed irrigation, in combination with deliberate agroforestry techniques. There may be some important lessons to be learnt today from these strategies for sustainable rural development in the Andes in the light of future climate uncertainty.
Global and Planetary Change, Sep 1, 2020
Abstract Numerous palaeoclimatic and prehistoric reconstructions have been reported at both the l... more Abstract Numerous palaeoclimatic and prehistoric reconstructions have been reported at both the local scale and across the very large area of tropical Central Africa, clearly highlighting the Late Holocene Rainforest Crisis (LHRC) which mainly developed from ca. 2500 to 2000 yr BP. The broad synchroneity of this interval is striking and has been revealed in many different deep lakes from humid or montane forest, lakes or swamps marginal to tropical forest, and swamp forests where the oscillations of the surface water table produce temporary emersions. In parallel, a chronological review is presented of the Bantu arrival in these areas, including indicators for burning, metallurgy and land clearance. Nevertheless, evidence of human occupation, such as artefacts or deposits containing charcoal is exceptional and generally absent in most areas. Although the archaeological data exhibit a gradual southward densification of human occupation throughout Central Africa, the increase of settlements clearly began after 2350 yr BP, not before 2500 BP. However, some authors have interpreted the geochemical signal of increased erosion in the Congo Basin or the opening up of the forest around Lake Barombi Mbo in Cameroon as being attributed to agricultural clearance, or even the supply of charcoal required for metallurgy. In short, these early Bantu settlers (in such modest densities) may have been responsible for some local landscape degradation (clearance, fire, metallurgy), but these same settlers could not, under any circumstances and across all Central Africa, be held responsible directly or indirectly for the synchronous changes of lake levels, draining vast swamps and opening up of the tropical forest canopy, which was due to an increased dry season, while the recovery with the recolonization of light demanding species, including oil palms (Elaeis guineensis) assisted by dispersers such as chimpanzees, was likewise due to natural processes. Therefore, it can be concluded that no data available validate the hypothesis that the major erosion or vegetation destruction ca. 2500 yr BP, was the result of large population movements. Indeed, the evolution of the environments of Central Africa are linked to the natural responses induced by general palaeoclimatic processes, observed synchronously not only in northern and eastern Africa, but globally. The natural recovery and resilience of these forests until the last centuries contrasts with the situation currently being faced.
Antiquity, Dec 1, 1996
A lake-sediment sequence from Marcacocha in the central Peruvian Andes provides a well-dated and ... more A lake-sediment sequence from Marcacocha in the central Peruvian Andes provides a well-dated and continuous vegetation record from an area rich in Inca and pre-Inca remains over the last 4000 years. Climatic changes in this record at AD 1–100 and AD 900–1050 seem to be broadly contemporaneous with major arid events from Lake Chichancanab, Mexico, affecting the Maya civilization and corroborated by the Quelccaya and Huascaran ice cores in Peru.
Quaternary Research, 2005
A 90,000-yr record of environmental change before 18,000 cal yr B.P. has been constructed using p... more A 90,000-yr record of environmental change before 18,000 cal yr B.P. has been constructed using pollen analyses from a sediment core obtained from Salar de Uyuni (3653 m above sea level) on the Bolivian Altiplano. The sequence consists of alternating mud and salt, which reflect shifts between wet and dry periods. Low abundances of aquatic species between 108,000 and 50,000 yr ago (such as Myriophyllum and Isoëtes) and marked fluctuations in Pediastrum suggest generally dry conditions dominated by saltpans. Between 50,000 yr ago and 36,000 cal yr B.P., lacustrine sediments become increasingly dominant. The transition to the formation of paleolake bMinchinQ begins with marked rises in Isoëtes and Myriophyllum, suggesting a lake of moderate depth. Similarly, between 36,000 and 26,000 cal yr B.P., the transition to paleolake Tauca is also initiated by rises in Isoëtes and Myriophyllum; the sustained presence of Isoëtes indicates the development of flooded littoral communities associated with a lake maintained at a higher water level. Polylepis tarapacana-dominated communities were probably an important component of the Altiplano terrestrial vegetation during much of the Last Glacial Maximum (LGM) and previous wet phases.
Journal of Archaeological Science, Feb 1, 2019
The ability of sedimentary proxies (especially dung fungal spores) to reflect the past presence a... more The ability of sedimentary proxies (especially dung fungal spores) to reflect the past presence and density of large herbivores on a landscape has been receiving increasing scrutiny. Here we examine the Sporormiella spore record from a well-dated, multiproxy, highly organic sedimentary record from the small lake basin of Marcacocha in the Cuzco region of Peru. The basin, a wetland since ca. AD 1840, existed as a small lake for at least 4000 years prior. Previous work at Marcacocha has shown that changes in herbivore densities reflect the abundances of oribatid mites preserved in the lake sediments. This study tests the assumption that both the Sporormiella and the oribatid mite records responded in broadly the same way to changes in herbivore densities over the past 1200 years. Analysis reveals a very low covariance between concentrations of Sporormiella spores and the two major components of the oribatid mite assemblage: a single aquatic species of Hydrozetes and a less abundant, wider grouping comprising members of the mostly terrestrial superfamily Ceratozetoidea (referred to as the 'ceratozetoids'). Variations in the Hydrozetes assemblage clearly dovetail with known historical events, including the massive decline of indigenous and camelid populations following the collapse of the Inca Empire in the mid-sixteenth century. Comparison with other environmental proxies from the Marcacocha sequence, including diatoms and charophyte oospores, suggests that the ceratozetoids appear to reflect increasing terrestrialization. In contrast, although the Sporormiella record indicates the presence of livestock, it fails to register the major historical changes in herbivore presence, though reflects well episodes of lake-level lowering. In small lake settings, therefore, the use of Sporormiella to estimate the density of herbivores in the catchment might be considered a relatively blunt instrument when compared with some other indicators. Supporting Information: Appendix S1 Comparison of Sporormiella dung fungal spores and oribatid mites as indicators of large herbivore presence: evidence from the Cuzco region of Peru
Mountain Research and Development, May 1, 1998
... Titles, Tracing 4,000 years of environmental history in the Cuzco area, Peru, from the pollen... more ... Titles, Tracing 4,000 years of environmental history in the Cuzco area, Peru, from the pollen record. Personal Authors, Chepstow-lusty, AJ,Bennett, KD,Fjeldsa, J.,Kendall, A.,Galiano, W.,Tupayachi Herrera, A. Publication Date, (May 1998). AGRIS Subj. Cat. ...
Fundamental and Applied Limnology, Jul 21, 2000
Areas within the rainforests of south-west Tasmania, home to Aboriginal tribes for more than 36,0... more Areas within the rainforests of south-west Tasmania, home to Aboriginal tribes for more than 36,000 years, were dramatically changed in the late 1800s with the arrival of European prospectors. Subsequent large-scale mining and smelting operations resulted in acid rain, local deforestation and extensive soil erosion. Much of the area is now bare rock. The aims of this study were to examine the terrestrial and lacustrine responses to industrial acidification and deforestation as revealed by a sediment core from 'Owen Tarn', a small cirque lake down-wind of the mining town of Queenstown, and adjacent to a World Heritage Area. Terrestrial responses were investigated using pollen analysis to document both the state of the rainforest before and after the arrival of the Europeans. Limnological responses were documented by examining changes in diatom communities in the core. Results show both the terrestrial vegetation and the aquatic microscopic vegetation have been considerably modified by mining activities in the last 100 years. Pollen analysis provides a chronology of industrial deforestation and diatom analysis shows changes in species composition and a decline in species richness. Indirect ordination (PCA) of sediment diatom assemblages in the core with autecological data from 76 Tasmanian highland lakes (TASDIAT) reveals that diatom assemblages in the bottom parts of the core are analogous to those of Tasmanian oligotrophic corridor lakes' while recent species assemblages are similar to those of acidic Tasmanian 'western lakes'. Although a number of cosmopolitan' species indicative of lake acidification in the northern hemisphere are present in Owen Tarn, acidification has resulted in a different species response.
Latin American Antiquity, Jun 1, 2009
The lower Ica Valley on the hyperarid south coast of Peru is today largely depopulated and bereft... more The lower Ica Valley on the hyperarid south coast of Peru is today largely depopulated and bereft of cultivation, yet its extensive archaeological remains attest to substantial prehispanic populations. This paper describes archaeological investigations to retrace changes in geomorphology, ecology, and land-use in Samaca, one of the riparian oasis basins of the lower Río lea, with the aim of investigating when, how, and why such changes took place. Archaeological interpretations of culture change in the region often invoke the impacts of major ENSO perturbations (El Niño). While our investigations confirm that major El Niño events around the end of the Early Intermediate Period likely offer part of the explanation for marked landscape change in the Samaca Basin, we also demonstrate the significance of more gradual, human-induced destruction of Prosopis pallida (huarango) riparian dry-forest. Huarango is a remarkable leguminous hardwood that lives for over a millennium and provides forage, fuel, and food. Moreover, it plays a crucial role in integrating fragile desert ecosystems, enhancing soil fertility and moisture, and accomplishing desalination and microclimatic amelioration. We propose that south coast valleys remained densely forested well into the Early Intermediate Period, attenuating the impact of El Niño events and supporting hitherto underappreciated agroforestry adaptations. Gradual deforestation eventually crossed an environmental threshold: river and wind erosion increased dramatically and precipitated radical desertification, feeding back into cultural changes in the Middle Horizon. Thus we argue Prosopis-human ecological relationships merit proper recognition in our archaeological interpretations of the south coast of Peru.
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Papers by Alex Chepstow-Lusty
that major ElNiño events around the end of the Early Intermediate Period likely offer part of the explanation for marked landscape change in the Samaca Basin, we also demonstrate the significance of more gradual, human- induced destruction of Prosopis pallida (huarango) riparian dry- forest. Huarango is a remarkable leguminous hardwood that lives for over a millennium and provides forage, fuel, and food. Moreover, it plays a crucial role in integrating fragile desert ecosystems, enhancing soil fertility and moisture, and accomplishing desalination and microclimatic amelioration. We propose that south coast valleys remained densely forested well into the Early Intermediate Period, attenuating the impact of El Niño events and supporting hitherto underappreciated agroforestry adaptations. Gradual deforestation eventually crossed an environmental threshold: river and wind erosion increased dramatically and precipitated radical desertification, feeding back into cultural changes in the Middle Horizon. Thus we argue Prosopis- human ecological relationships merit proper recognition in our archaeological interpretations of the south coast of Peru.