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1.
Discussions of dispersals of early hominins from Africa assume that Southwest Asia and the Arabian Peninsula were the primary passageways for migrations to Eurasia. The Mediterranean is usually viewed as a barrier to early hominin movements because pre‐sapiens hominins were thought to lack the technical means or the cognitive skills to construct boats. The discovery of early Palaeolithic artefacts in an archaeological survey on the Greek island of Crete challenges this view. Here we show that Palaeolithic artefacts in the Plakias region in southwestern Crete are associated with geological contexts that can be dated to the late Middle or early Late Pleistocene. Because Crete has been separated from the mainland throughout the Pleistocene, the presence of Pleistocene age artefacts there suggests that early hominins were able to cross open water. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

2.
Major hydrological variations associated with glacial and interglacial climates in North Africa and the Levant have been related to Middle Paleolithic occupations and dispersals, but suitable archaeological sites to explore such relationships are rare on the Arabian Peninsula. Here we report the discovery of Middle Paleolithic assemblages in the Nefud Desert of northern Arabia associated with stratified deposits dated to 75,000 years ago. The site is located in close proximity to a substantial relict lake and indicates that Middle Paleolithic hominins penetrated deeply into the Arabian Peninsula to inhabit landscapes vegetated by grasses and some trees. Our discovery supports the hypothesis of range expansion by Middle Paleolithic populations into Arabia during the final humid phase of Marine Isotope Stage 5, when environmental conditions were still favorable.  相似文献   

3.
The vegetation and the climatic context in which the first hominins entered and dispersed in Europe during the Early Pleistocene are reconstructed, using literature review and a new climatic simulation. Both in situ fauna and in situ pollen at the twelve early hominin sites under consideration indicate the occurrence of open landscapes: grasslands or forested steppes. The presence of ancient hominins (Homo of the erectus group) in Europe is only possible at the transition from glacial to interglacial periods, the full glacial being too cold for them and the transition interglacial to glacial too forested. Glacial–interglacial cycles forced by obliquity showed paralleled vegetation successions, which repeated c. 42 times during the course of the Early Pleistocene (2.58–0.78 Ma), providing 42 narrow windows of opportunity for hominins to disperse into Europe.The climatic conditions of this Early Pleistocene vegetation at glacial-interglacial transitions are compared with a climatic simulation for 9 ka ago without ice sheet, as this time period is so far the best analogue available. The climate at the beginning of the present interglacial displayed a stronger seasonality than now. Forest cover would not have been hampered though, clearly indicating that other factors linked to refugial location and soils leave this period relatively free of forests. Similar situations with an offset between climate and vegetation at the beginning of interglacials repeated themselves throughout the Quaternary and benefitted the early hominins when colonising Europe.The duration of this open phase of vegetation at the glacial–interglacial transition was long enough to allow colonisation from the Levant to the Atlantic.The twelve sites fall within rather narrow ranges of summer precipitation and temperature of the coldest month, suggesting the hominins had only a very low tolerance to climate variability.  相似文献   

4.
A Late Quaternary permafrost profile from the Labaz Lake area (Taymyr Peninsula, Central Siberia) has been investigated using analyses of diatoms, pollen, sedimentology and geochemistry. A sedimentation gap for the termination of the Pleistocene and the start of lacustrine sedimentation in the Boreal can be inferred. At that time shallow-lake conditions prevailed and a connection to the Labaz Lake is probable. The diatom data provide indications for the assessment of the Holocene environmental development of the study site in more detail. The most favourable climatic conditions and comparatively higher water level stands are inferred for the early Atlantic. Towards the end of this period the gradual transition to a wetland with poor-fen character took place. Within the Subboreal there was a short episode with mild climate conditions. At that time the last trees occurred in the Labaz Lake area and somewhat higher water level stands were likely. The Subatlantic climate deterioration led to further drying up of the wetland along with a lowering of water pH and permafrost aggradation. The transition from a locality with low-centre to one with high-centre polygons is still underway.  相似文献   

5.
Cold-adapted large mammal populations spread southward during the coldest and driest phases of the Late Pleistocene reaching the Iberian Peninsula. Presence of woolly rhinoceros (Coelodonta antiquitatis) can be identified from 23 Iberian sites, which is compiled and analyzed herein, and the fossil specimens from seven of these sites are described here for first time.Morphological and biometrical analyses demonstrate that the Iberian woolly rhinoceros did not significantly differ from individuals of other European populations, but represent the westernmost part of a continuous Eurasian belt of distribution.The first presence of woolly rhino in the Iberian Peninsula has been identified during the late Middle Pleistocene and early Late Pleistocene. However, the highest abundance of this species is recorded during MIS 3 and 2. The latest Iberian occurrences can be dated around 20 ka BP. The presence of woolly rhinoceros in the Iberian Peninsula correlates with periods of extreme dry and cold climatic conditions documented in Iberian terrestrial and marine sediment sequences.From a palaeobiogeographic point of view, the maximum southern spread of C. antiquitatis on the Iberian Peninsula was registered during the late Middle Pleistocene or early Late Pleistocene, reaching the latitude of Madrid (about 40°N). Subsequently, during MIS 3 and 2, all Iberian finds were restricted to the Northern regions of Iberia (Cantabrian area and Catalonia). The southern expansion of C. antiquitatis during the Late Pleistocene in the Iberian Peninsula reached similar latitudes to other Eurasian regions.The ecological composition of fossil assemblages with presence of woolly rhinoceros was statistically analyzed. Results show that temperate ungulate species are predominant at Iberian assemblages, resulting in a particular mixture of temperate and cold elements different of the typical Eurasian cold-adapted faunal associations. This particular situation suggests two possible explanations: a) Eventual migrations during the coldest time spans, resulting in a mixing of cold and temperate faunas, instead a faunal replacing; b) Persistence of woolly rhinoceros populations in the Iberian Peninsula during interglacial episodes confined at cryptic southern refugia.  相似文献   

6.
The Galicia Interior Basin (GIB; NW Iberian Peninsula) is located near a critical transition between the subtropical (temperate) and subpolar (cold) gyres of the North Atlantic. It therefore witnesses oceanographic changes driven by global climatic events. This study reports on the recent (latest Pleistocene) sedimentary, palaeoceanographic and palaeoclimatic history of the basin. We integrated analysis of deep‐sea sediment cores retrieved from an E–W transect across the GIB. The analysis indicated three types of sedimentary processes recording glacial (Marine Isotope Stage 2–4) and deglacial events: along‐slope bottom currents (forming contourite deposits), pelagic and hemipelagic sedimentation, and gravitational dislocation. Variation in depositional patterns and sedimentation rates indicate distinctive transport (along‐slope and down‐slope) and depositional processes. These in turn reflect climatic and oceanographic drivers. We interpret changes in sea level from core evidence showing changes in sediment supply. The cores exhibited conspicuous sedimentary evidence of Heinrich events (HEs). The stratigraphic intervals associated with HEs showed significant lateral variation. We suggest that the lateral variation may result from the development of an oceanographic boundary between surface water masses with different temperature and salinity parameters or changes in surface currents which may have introduced relatively warmer water into the GIB during the last glacial period.  相似文献   

7.
Cover sediments of the York Terrace exposed near the California River, western Seward Peninsula, Alaska, yield mollusks, ostracodes, and foraminifera that lived during the Anvilian transgression of early Pleistocene age. The fossiliferous sediments lie at the inner edge of the York Terrace, a deformed wave-cut platform that extends eastward from Bering Strait along much of the southern coast of Seward Peninsula. The seaward margin is truncated by the little-deformed Lost River Terrace, carved during the Pelukian (Sangamonian) transgression. The early Pleistocene sediments seem to have been deposited between the first and second of four glaciations for which evidence can be found in the California River area.The California River fauna includes several extinct species and several species now confined to areas as remote as the northwestern Pacific and north Atlantic. The fauna probably lived in water temperatures much like those of the present time but deeper water on the Bering Shelf is suggested.The presence of an early Pleistocene fauna at the inner edge of the York Terrace at California River shows that the terrace was largely carved before and during early Pleistocene time. However, a marine fauna apparently of middle Pleistocene age is found on the York Terrace near Cassiterite Peak, and this seems to indicate that the terrace remained low until middle Pleistocene time. Uplift of the York Terrace probably was accompanied by uplift of Bering Strait. The strait may have been deeper, and there may have been no land bridge between the Seward Peninsula of Alaksa and the Chukotka Peninsula of Siberia during most of early and middle Pleistocene time.  相似文献   

8.
An outcrop study of uplifted marine terraces provides information on the climate of past sea‐level maxima, supplementing existing palaeoclimatological archives. The western coast of the Akamas Peninsula shows several uplifted and intricately stacked Quaternary marine terraces. This study focuses on the sedimentology, petrography and sequence stratigraphy of the last three recent terraces and provides palaeoclimatological reconstruction and chronological framing. All three terraces display basically the same stratigraphic succession, which consists of regressive sequences ranging from bioturbated, storm‐influenced, subtidal high‐energy sands to subaerial exposure and aeolian deposition. Each sequence differs in petrography, reflecting contemporaneous climatic conditions. The first studied sequence (Marine Isotope Stage 9 or 11?) was deposited in a warm, arid climate, with oligotrophic water favouring ooid formation. The second sequence (Marine Isotope Stage 7) displays colder but humid conditions, with lower carbonate production and strong detrital input. The third sequence (Marine Isotope Stage 5e) records warm, humid conditions, with high carbonate production combined with significant detrital input. These littoral terraces offer high‐quality outcrops of glacioeustatic‐dominated, littoral sedimentology, together with evidence indicative of the regional climate during the late Pleistocene.  相似文献   

9.
Bizat Ruhama, an Early Pleistocene site located in the southern coastal plain of Israel, has yielded a single archaeological horizon dating to the Matuyama chron. Recent technological and zooarchaeological studies suggest evidence of near in situ hominin occupations taking place in a semiarid climatic setting. Such an archaeological context is rare for the Early Pleistocene and must be corroborated through reconstruction of site formation processes. This paper offers a microstratigraphic view of the site based on results from a micromorphological and granulometric study aimed at reconstructing site formation processes. Results show that the bone and lithic specimens were deposited near their excavated provenience, in a depressed, seasonally waterlogged area, and were subsequently slightly displaced and buried by surface sediment. We infer that the Bizat Ruhama deposit represents one or a few hominin occupations taking place on the surface of an undulating inter‐dune depression under a semiarid Mediterranean climate. © 2010 Wiley Periodicals, Inc.  相似文献   

10.
The water demand in arid regions is commonly covered by groundwater resources that date back to more humid periods of the Pleistocene and Holocene. Within the investigated arid part of SE Saudi-Arabia information about climate, groundwater levels, and pumping rates are only available for regions where groundwater extractions occur at present-day. For the prediction of the impact of long-term climate changes on groundwater resources an understanding of the hydrogeological and hydrological past and the development of the aquifers is necessary. Therefore, all available information about hydrology and hydrogeology for the past 10,000 years BP were collected and compiled to a conceptual model of the aquifer development on the Arabian Peninsula since the last Ice-Age. The climatic history was displayed by changes in precipitation, temperature and recharge during the mid-S and late Holocene. The hydrogeological development is described by groundwater ages, sea level fluctuations, movement of the coastline, and the development of sabkhas. The most sensitive parameter to describe the development of aquifer system is recharge. Present-day recharge was calculated with the hydrological model system HEC-HMS accounting for current precipitation, temperature, wind, soil types, and geomorphology. With respect to changes in precipitation and temperature over the past 10,000 years the temporal and spatial variability of groundwater recharge was calculated using empirical equations valid for semi-arid and arid settings. Further inflow into the groundwater system results from surface water infiltration in wadi beds, while natural outflow from the groundwater system occurs by discharge to the Gulf, evaporation from sabkhas, and spring discharge. Backward predictions can be verified by sedimentological observations of palaeo-river systems and lakes indicating that groundwater levels reached temporarily the surface under wetter climate conditions and 14C groundwater ages displaying groundwater residence times.  相似文献   

11.
A hominin maxilla, discovered in 1983 in Chaoxian County, Anhui Province, eastern China represents one of several Asian hominins dating to the late Middle Pleistocene. Although the maxilla and associated occipital have been described, no detailed study of the dentition has been made. This study provides metrical and morphological information on the Chaoxian dentition and places it into a larger Middle to Late Pleistocene context. Implications for the taxonomy of Middle Pleistocene hominins are discussed.  相似文献   

12.
Continental sediments and geomorphological features of the coastal Wahiba Sands, Sultanate of Oman, reflect environmental variability in southeastern Arabia during the late Quaternary. Weakly cemented dune sands, interdune deposits and coastal sediments were dated by luminescence methods to establish an absolute chronology of changes in sedimentary dynamics. The dating results confirm previous assumptions that during times of low global sea level sand was transported by southerly winds from the exposed shelf onto the Arabian Peninsula. Two prominent phases of sand accumulation in the coastal area took place just before and after the last glacial maximum (LGM). A final significant period of dune consolidation is recognised during the early Holocene. However, no major consolidation of dunes appears to have occurred during the LGM and the Younger Dryas. In the northern part of the Wahiba Sands, these two periods are characterised by substantial sand deposition. This discrepancy is explained by the lack of conservation potential for dunes in the coastal area, probably caused by a low groundwater table due to low sea level and decreased precipitation. While the times of aeolian activity reflect arid to hyper‐arid conditions, lacustrine and pedogenically altered interdune deposits indicate wetter conditions than today caused by increased monsoonal circulation during the Holocene climatic optimum. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

13.
We propose a population model for Middle Pleistocene Europe that is based on demographic “sources” and “sinks”. The former were a small number of “core” or populations in glacial refugia in southern Europe from which hominins expanded northwards in interstadial and interglacial periods; occupation outside glacial refugia would have been restricted to warm or temperate periods, and populations at the northern limit of the Middle Pleistocene range would have been “sink” populations in that they depended upon recruitment from source populations further south. Southwest Asia would also have been a likely source of immigrant, source populations. We argue as an alternative to an “ebb and flow” model in which groups retreated to refugia when conditions worsened that local extinction outside refugia would have been frequent. In extreme situations, Europe may have been a population “sink” (i.e. unpopulated) that was replenished from source populations in Southwest Asia. We suggest that this pattern of repeated colonisation and extinction may help explain the morphological variability of European Middle Pleistocene hominins, particularly Homo heidelbergensis and its apparent non-lineal evolution towards Homo neanderthalensis.  相似文献   

14.
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15.
Cenotes (natural wells or sinkholes) comprise the most common landscape features in the northern Maya Lowlands of the Yucatán Peninsula, México. Detailed study of dated soil‐sedimentary sequences, recovered from a cenote at the archaeological site T’isil and nearby wetlands, allows a partial reconstruction of environmental variability at the site for the last 2000 years. Biogenic calcite sedimentation and Calcisol development occur during three intervals of increased inundation in cenote and wetland environments, ca. A.D. 300, A.D. 1000, and A.D. 1300. Periods of increased inundation in the cenote and wetlands correlate with wetter climatic intervals, and periods of Maya occupation at sites in the Yalahau region. Evidence for Maya modification of the cenote environment may relate to regional wetland agricultural practices.  相似文献   

16.
Lithological and biological features of a fossiliferous tufa in the Kapthurin Formation, Baringo, Kenya, reveal the presence of a lush wetland in a semi-arid environment during the Middle Pleistocene ( ca 500 ka) in this portion of the East African Rift Valley. Four geological sections, each between 3 m and 8 m in thickness, exposed over a distance of 0·5 km, reveal a 1 to 2 m thick paludal tufa which is composed of three carbonate beds, two dark grey silty claystones and a reddish-brown silty palaeosol. High resolution stratigraphic analysis, carbonate petrography, stable isotope and elemental geochemistry, clay mineralogy and fossil remains (molluscs, ostracods, diatoms and charophytes) reveal a ground water-fed system that fluctuated in depth and periodically disappeared altogether. Oxygen isotope ratios (δ18O) of tufa matrix range from −4·5‰ to −8·0‰ (Vienna Pee Dee Belemnite) and become more positive up section, indicating the decreasing influence of fault-related fluids and increasing residence time or freshness of wetland water, rather than evaporative enrichment. This spring was situated on a lake margin during low lake levels, thrived during periods of increased ground water input and was ultimately replaced by an alkaline lake. The wetland would appear to have existed during a cool interval within the generally warm Marine Isotope Stage 13 or perhaps during the warm second half of Marine Isotope Stage 13. The ground water source of this wetland arose through a fault system. Thus, the position of the tufa deposit is controlled structurally but the timing and duration of the wetland system may have been influenced by both climatic and tectonic factors.  相似文献   

17.
Jin, Z. D., Bickle, M. J., Chapman, H. J., Yu, J., An, Z., Wang, S. & Greaves, M. J. 2010: Ostracod Mg/Sr/Ca and 87Sr/86Sr geochemistry from Tibetan lake sediments: Implications for early to mid‐Pleistocene Indian monsoon and catchment weathering. Boreas, 10.1111/j.1502‐3885.2010.00184.x. ISSN 0300‐9483 Lacustrine sediment serves as a valuable archive for tracing catchment weathering processes associated with past climatic and/or tectonic changes. High‐resolution records of fossil ostracod Mg/Ca, Sr/Ca and 87Sr/86Sr ratios from a lake sediment core from the central Tibetan Plateau reveal a temporal link between lake‐water chemistry and catchment weathering and distinct monsoonal oscillations over the early to mid‐Pleistocene. Between 2.01 and 0.95 Ma, lake‐water chemistry was dominated by a high proportion of carbonate weathering related to variations in the Indian monsoon, resulting in relatively low and constant ostracod 87Sr/86Sr but obvious fluctuations in Mg/Ca, Sr/Ca and δ18O. Across the mid‐Pleistocene transition (MPT), a significant increase in 87Sr/86Sr and frequently fluctuating ratios of ostracod Mg/Ca, Sr/Ca and δ18O are coincident with increases in both Chinese loess grain size and Arabian Sea lithogenic flux. This correlation indicates an increased glaciation and a strong monsoon seasonal contrast over the plateau. The increase in lake‐water 87Sr/86Sr across the MPT highlights a change in catchment weathering patterns, rather than one in climate‐enhanced weathering intensity, with an increased weathering of 87Sr‐rich minerals potentially induced by marked extensive glaciation and strong seasonality in the central plateau.  相似文献   

18.
Wetland ecosystems are particularly vulnerable due to flow of nutrients from the surrounding watershed. The study was performed in the Shadegan wetland, a Ramsar-listed wetland located in the south-west of Iran at the head of the Persian Gulf. The wetland plays a significant hydrological and ecological role in the natural functioning of the northern Gulf. The proposed wetland has different water quality characteristics in wet and dry years of study during 1994–2006. To determine the variables, sampling was carried seasonally for each year at six stations. The results indicate that wetland in wet years had high concentrations of nitrate and silicate, leading to oligo–meso eutrophic conditions. Wetland in dry years had high phosphate concentrations, resulting in meso-eutrophic conditions. Forcing functions, such as climatic patterns, water residence time, reduce runoff and increasing density of wastewaters from the surrounding urban, agricultural and industrial area are probably the main variables that explain the observed patterns.  相似文献   

19.
Fort Morgan Peninsula is an attached portion of a dynamic barrier complex in the northern Gulf of Mexico and is a large tourist area that brings in a significant amount of revenue for Alabama. Many of the hotels and tourist attractions depend on the groundwater as their water supply. The over-withdrawal of groundwater and saltwater intrustion will have a negative impact on the ecology, tourism and economy if groundwater resources are not properly monitored and managed. In this study a calibrated groundwater flow model was used to analyze the sustainability of groundwater resources at Fort Morgan Peninsula. Detailed flow budgets were prepared to check the various components of inflow and outflow under different water use and climatic conditions. The results indicated the locations where groundwater was over-pumped and subjected to saltwater intrusion, or will be subjected to saltwater intrusion under a range of projected water use and climatic conditions.  相似文献   

20.
Coastal dune systems consisting of allochemical grains are important sedimentary archives of Pleistocene age in both of the hemispheres between the latitudes of 20° to 40°. The south Saurashtra coast in western India exhibits a large section of Middle Pleistocene aeolianites in the form of coastal cliffs, which is famous as ‘Miliolite’. Miliolites of Gopnath in south‐east Saurashtra are the oldest known coastal aeolianite deposits (age >156 ka which corresponds to Marine Isotope Stage 6) in western India. Aeolian deposits of similar ages have also been reported from the Thar Desert in north‐west India and from Southern Arabia which were largely controlled by the south‐west monsoon wind system that affects the entire belt corresponding to Sahara–Sahel, the Arabian Peninsula and north‐western India. Miliolite deposits in Gopnath are characterized by grainfall, grainflow and wind ripple laminations. At least three types of aeolian bounding surfaces have been identified. Five major facies have been identified which represent the dune and interdune relationship within the coastal aeolian system. The major dune bodies are identified as transverse dune types. The Gopnath aeolianites were deposited under dominantly dry aeolian conditions. Facies association reveals two different phases of aeolian accumulation, namely initiation of aeolian sedimentation after a prolonged hiatus and the establishment of a regularized aeolian sedimentation system. While initiation of aeolian sedimentation is marked by vast stretches of sheet sand with occasional dune bodies, the overlying thick, tabular, laterally extensive cross‐stratified units manifest regular aeolian sedimentation. However, the dune building events in Gopnath were interrupted by development of laterally extensive palaeosol horizons. Eustasy and climate exerted the major allogenic controls on the aeolian sedimentation by affecting the sediment budget as well as influencing the sedimentation pattern.  相似文献   

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