Phytolith analysis from the archaeological site of Kush, Ras al-Khaimah, United Arab Emirates

Despite the wealth of archaeological sites and excellent conditions for preservation, few phytolith investigations have been undertaken from the Arabian Gulf region. The results from the Sasanian and Islamic archaeological tell of Kush, Ras al-Khaimah, United Arab Emirates, are presented. Kush is situated just inside the Gulf on an important trade route. The occupation sequence dates from the 4^th century A.D. until the 13^th century A.D., recording the development of the site in the Sasanian period, followed by the arrival of Islam in the 7^th century A.D. and the final abandonment of the site in the late 13^th century when the nearby site of al-Mataf (Julfar) began to develop closer to the present day coastline. All the samples analyzed contained abundant phytoliths (short cells, elongated cells, and groups of elongated cells) of various types. They included date palm (Phoenix dactylifera), papillae (possibly from barley (Hordeum)), and hair cells possibly from species of canary grass (Phalaris spp.). Some researchers have suggested that groups of elongated cells may indicate the presence of irrigation in semiarid environments. The present results for this class of phytoliths appeared to imply that intensive irrigation was unlikely to have taken place around Kush.     

Relationships between Holocene sea-level variations,trophic development,and climatic change in Negra Lagoon,Southern Uruguay

Paleolimnological data are presented on trophic development, climatic change and sea level variations in Negra Lagoon, a 142 km² coastal lagoon in southern Uruguay. Using a sediment core that extended to the early Holocene, analyses of organic matter, carbonate, diatoms and opal phytoliths allowed us to track changes in trophic state and paleosalinity levels, which were closely related to Holocene sea level variation, temperature and humidity. Diatom Association Zones (DAZ) corresponding to transgressive events were dominated by marine/brackish taxa and relatively low organic matter values, while those DAZ corresponding to regressive events showed increases in brackish/freshwater diatoms and organic matter. Opal Phytoliths Association Zones (OPAZ) also were identified, temperature and humidity indices were calculated, and climatic trends were inferred. During the middle Holocene (i.e., ~5000–4000 yr BP), cool–dry climatic conditions were established. After ~4000 yr BP, a transition from cool to warm–humid conditions was observed, but fully warm humid conditions established only after ~1700 yr BP. Such climatic amelioration led to increases in trophic state.     

Late Holocene Neoglacial conditions from the Lesotho highlands, southern Africa: phytolith and stable carbon isotope evidence from the archaeological site of Likoaeng

The late Holocene environmental history of the Lesotho highlands, southern Africa, is poorly understood with few detailed studies to date. At Likoaeng, Senqu Valley, Lesotho, a 3 m stratified sedimentary sequence from an open-air archaeological site records vegetation development for the period 3400-1070 cal. BP. Phytolith analyses and bulk sediment organic matter δ¹³C indicate that C₄ grassland dominated the lower part of the sequence until approximately 2960 cal. BP when there was a switch to C₃ Pooid grassland (2960-2160 cal. BP). Also noted was a change from hunting mainly bovids to a dominance of fishing at the site. The change in grassland type and archaeological subsistence strategies corresponds with an episode of neoglacial cooling and the expansion of Alpine sourgrasses into lower altitudes. From 2160 to 1600 cal. BP grassland became a mix of C₃ and C₄ types and by 1600-1070 cal. BP there was a return to C₄ dominated grassland. During this latter phase there was a reversal from fishing to hunting again (and eventually some keeping of domestic livestock) at the site. These data outline the vegetation response to latitudinal shifts of frontal systems, and relatively strong atmospheric circulation variability, perhaps underpinned by variations of polar water into the Benguela Current during the late Holocene.     

A spring and wooded habitat at FLK Zinj and their relevance to origins of human behavior

The 1959 discovery of the hominin fossil Zinjanthropus boisei brought the world's attention to the rich records at Olduvai Gorge, Tanzania. Subsequent excavations of archaeological level 22 (FLK Zinj) Bed I uncovered remains of Homo habilis and a high-density collection of fossils and Oldowan stone tools. The occurrence of this unusual collection of bones and tools at this specific location has been controversial for decades. We present paleoecological data that provide new insights into the origin of FLK Zinj. Our recent excavations 200 m north of the site uncovered a 0.5-m-thick tufa mound draped by Tuff IC, in the same stratigraphic horizon as level 22. Stable isotope analyses indicate that the carbonates were deposited by a freshwater spring. Phytolith analysis of the waxy clay under Tuff IC revealed abundant woody dicotyledon and palm phytoliths, indicating that the site was wooded to densely wooded. The time equivalency and close physical proximity of the two environments indicate the two are related. This study has provided the first documented evidence of springs in Bed I and these data have important implications for the interpretation of hominin behavior in meat acquisition and the ongoing debate on scavenging versus hunting.     

Vegetation and climate change since 14,810 C yr B.P. in southeastern Uruguay and implications for the rise of early Formative societies

This article presents a combined pollen and phytolith record of a 1.70-m sediment core from the wetlands of India Muerta (33° 42′ S, 53° 57′ W) in the lowland Pampa (grasslands) of southeastern Uruguay. Six ¹⁴C dates and the pollen and phytolith content of the samples permitted the recognition of four distinct climatic periods between 14,850 ¹⁴C yr B.P. and the present. The Late Pleistocene period (between ca. 14,810 and ca. 10,000 ¹⁴C yr B.P.) was characterized by drier and cooler conditions indicated by the presence of a C3-dominated grassland. These conditions prevailed until the onset of the warmer and more humid climate of the Holocene around 9450 ¹⁴C yr B.P. The early Holocene (between around 10,000 and 6620 ¹⁴C yr B.P.) was characterized by the establishment of wetlands in the region as evidenced by the formation of black peat, the increase in wetland taxa, and the replacement of C3 Pooideae by C4 Panicoideae grasses. During the mid-Holocene, around 6620 ¹⁴C yr B.P., began a period of environmental change characterized by drier climatic conditions, which resulted in the expansion of halophytic communities in the flat, low-lying areas of the wetlands of India Muerta. About 4020 ¹⁴C yr B.P. a massive spike of Amaranthaceae/Chenopodiaceae coupled with a radical drop in wetland species indicates another major and more severe period of dryness. After ca. 4000 ¹⁴C yr B.P., a decrease of halophytic species indicates the onset of more humid and stable climatic conditions, which characterized the late Holocene.The findings reported in this article substantially improve our knowledge of the late Glacial and Holocene climate and vegetation in the region. The data provide a detailed record of the timing and severity of mid-Holocene environmental changes in southeastern South America. Significantly, the mid-Holocene drying trend coincided with major organizational changes in settlement, subsistence, and technology of the pre-Hispanic populations in the region, which gave rise to early Formative societies. This study also represents the first combined pollen and phytolith record for southeastern South America reinforcing the utility of phytoliths as significant indicators of long-term grassland dynamics.     

Late Holocene palaeoenvironments of the Nutria Mansa 1 archaeological site,Argentina

This paper presents results of interdisciplinary palaeoenvironmental research carried out on a sediment sequence from the Nutria Mansa 1 archaeological site. This late Holocene site is located in the Pampean plains, Argentina. Siliceous microfossils were recorded (i.e. phytoliths, diatoms, chrysophytes, sponges) and micro-charcoal was analyzed. In addition, fauna identified at the site were correlated with regional palaeoclimatic evidence. Based on the microfossil associations, we concluded that the human occupations occurred beside a fluvial and brackish-freshwater lacustrine setting. Grass communities were located on its margins that developed under a warm temperate climate with evidence for dryness and marked seasonality in part of the record. Although some stratigraphic and faunal evidence indicates a possible temperature increase, these fluctuations were not sufficient to extirpate mammals of arid and cold environments.     

Phytoliths and seeds in fluvial island paleoenviroment reconstruction (interaction with pollen analysis)

We tested the use of phytoliths and seeds as bioindicators in the paleoenvironmental reconstruction of fluvial islands and compared the results with those of facies and pollen analyses. The studied material was taken from a 215 cm core drilled in Mutum Island. The study included a) the quantification and identification of phytoliths and seeds, b) the determination of the distribution of biological material in the island sediment and sedimentary facies, c) the determination of organic material contents, and d) a chronological analysis with three ¹⁴C dates. This study also determined the distribution of seeds and phytoliths over the sedimentary environment succession. We identified the following distributions of seeds and phytoliths over the paleoenvironmental hydrach succession. 1) Channel paleoenvironment (eupotamic stage): the sediment was deposited under lotic flow conditions, with the occurrence of Podostemaceae phytoliths and a predominance of Poliygonaceae seeds. 2) Blind channel paleoenvironment (parapotamic stage): this environment, which occurred 725–935 cal yrs BP., demonstrated an increase in the quantity of Podostemaceae phytoliths and seed quantity alternations. 3) Lake paleoenvironment (paleopotamic stage): a change from the blind channel to lake environment occurred at 631–797 cal yrs BP. An increase in the phytolith concentration was associated with a saddle morphology peak and general decrease in seeds, except for over the 110-100 cm interval, with a high occurrence of Cecropiaceae and Lentibulariaceae seeds. 4) Present swamp environment (paleopotamic to terrestrial stage): the present environment was settled approximately 300 cal yrs BP. (uncertainties range) with phytoliths. The seed assemblage in the sediment resembles the current vegetation on the island. The variation in the types of phytoliths and seeds from the base to the top of the sedimentary column reflect changes in the vegetation with changes in the environmental conditions and the great potential for these structures to be paleoindicators in fluvial systems. The seed and phytolith data were compared with the pollen analysis results.     

An analysis of phytolith assemblages for the quantitativereconstruction of late Quaternary environments of the Lower Taieri Plain,Otago, South Island, New Zealand I. Modern assemblages and transferfunctions

An analysis of modern phytolith assemblages is presented.Phytolith assemblages were studied in modern surface soils and sediments of 28sites from east Otago, New Zealand, within a range of vegetation types andmicroclimates. No simple distinction could be made between vegetation types onthe basis of phytolith assemblage composition. A Principal Components Analysis(PCA) of the phytolith data set revealed that festucoid, chloridoid andspherical phytolith morphotypes formed strong associations with sites fromwetland, grassland, and forest vegetation types, respectively. Moreimportantly, a comparison of sample replicates from each field site using Squared ChordDistance (SCD) assemblage analysis showed that wetland and grassland sitestended to produce more internally consistent phytolith assemblages than forestsites. Environmental variables including pH, conductivity, altitude,precipitation and temperature were also gathered for each site. The ability ofeach environmental variable to reflect variance in the entire phytolithdata set was estimated by a series of Redundancy Analyses (RDA) with MonteCarlo permutation tests of statistical significance. After a forward selectionprocess, transfer functions were generated using Partial Least Squares (PLS)regression and calibration with jack-knife validation. The final transferfunctions have root mean squared errors of prediction for pH (0.47), logconductivity (0.38 S cm), average annual precipitation (63mm), and average annual (0.28 °C), spring (0.38 °C) andautumn temperature (0.41 °C); the smallest group of environmental variablesexplaining the most variance in the modern phytolith data set. The most usefultransfer functions for application to fossil phytolith data andpaleoenvironmental interpretation are pH, log conductivity and annualprecipitation. The relationship between changes in pH and annual precipitationand phytolith assemblage composition found in this study presents aprima facie relationship with the potential to providedirect proxies for soil weathering and indirectly for paleoenvironmentalreconstruction.     

Phytolith evidence for C4-dominated grassland since the early Holocene at Long Pocket, northeast Queensland, Australia

Preliminary phytolith analysis of ephemeral lake fill sediment at Long Pocket, near Toomba, northeast Queensland, Australia, indicates that a C4-dominated grassland with a minor woody component has been present in the region since ca. 8000 cal yr B.P. Based on the modern distribution of C4 and C3 native grasses in Australia, this suggests that mean summer temperatures of at least 14°C (ca. 10°C cooler than present) were maintained since the early Holocene. This interpretation is comparable with previous studies, which together imply that the establishment of C4-dominated grasses in central and northeast Australia occurred between the last glacial maximum (most likely after ca. 16,000 ¹⁴C yr B.P.) and ca. 7200 ¹⁴C yr B.P. (ca. 8000 cal yr B.P.). Taxonomic composition of the grassland appears relatively consistent since the early Holocene at Long Pocket and includes phytoliths comparable with those from modern Arundinoideae, Panicoideae, and Chloridoideae. Rare non-grass phytoliths are also present. A gradual decrease in abundance of saddle phytolith forms (attributed to Chloridoideae grasses) from the base of the record at ca. 6500-7000 cal yr B.P. suggests decreasing aridity throughout the Holocene. This trend could reflect a locally drawn out effect of the end of the postglacial arid period due to the well-drained basalt flow catchment maintaining a local arid habitat for the Chloridoideae grasses.     

Ovi-caprid dung as an indicator of paleovegetation and paleoclimate in northwestern China

Diverse palynomorphs and phytoliths recovered from coprolites of ovi-caprids (sheep, goat) collected from Yang-Hai Tomb at Xinjiang Province, China, have been used to elucidate the dietary pattern of ancient livestock and to reconstruct the paleovegetation and paleoclimate of this part of northwest China ca. 2500 ¹⁴C yr BP. Palynological and phytolith data suggest that a rich dry temperate vegetation prevailed in the area during the said period. Climatic conditions and grassland vegetation type of the area are explored using phytolith indices.