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1.
An aeolian sand unit overlies the Middle Stone Age deposits at Blombos Cave on the southern Cape coast. These deposits contained culturally-important artefacts, including bone tools and pieces of engraved ochre, as well as a large number of worked lithics. The aeolian sand and two other remnants of the sand dune formed against the coastal cliff were dated using optical dating. To determine the dose received since deposition, measurements were made on 5mg aliquots of purified quartz grains using the single-aliquot regenerative-dose (SAR) protocol. The results of several internal check procedures are reported and at least 15 replicate dose determinations are presented for each sample. Combining these dose values with measurements of the radioactive content of each sample resulted in an age of 69.2+/-3.9 ka for the unit within the cave, and a mean age of 70.1+/-1.9 ka for all three dune samples. This provides a minimum age for the Middle Stone Age material at Blombos Cave.  相似文献   

2.
Optically stimulated luminescence (OSL) measurements are reported for both single aliquots (of two different sizes) and single grains of quartz from deposits within Blombos Cave. Ages have been obtained for six sediments from the Middle Stone Age (MSA) occupation levels and for two sterile sands, one underlying the archaeological sediment and one overlying the Later Stone Age occupation levels. The ages for the archaeological sediments were obtained from single-grain measurements that enabled unrepresentative grains to be rejected. The MSA occupation levels have ages that, within error limits, are in stratigraphic order and fall between the OSL age for the oldest dune sand (143.2+/-5.5 ka) and a previously published OSL age for the sterile sand ( approximately 70 ka) that separates the Middle and Later Stone Age deposits. The earliest MSA archaeological phase, M3, from where fragments of ochre were found as well as human teeth, is dated to 98.9+/-4.5 ka, coinciding with the sea-level high of oxygen isotope substage 5c. The cave then appears to be unoccupied until oxygen isotope substage 5a on the basis of four OSL ages for archaeological phase M2, ranging from 84.6+/-5.8 to 76.8+/-3.1 ka; these levels contained large hearths and bone tools. An age of 72.7+/-3.1 ka was obtained for the final MSA archaeological phase, M1, from which deliberately engraved ochre and shell beads were recovered along with bifacial stone points. We conclude that the periods of occupation were determined by changes in sea level, with abundant sources of seafood available in times of high sea level and with the cave being closed by the accumulation of large dunes during periods of low sea level, such as during oxygen isotope stages 4 and 6.  相似文献   

3.
The Kow Swamp people are a fossil population of robust modern humans. We report optically stimulated luminescence (OSL) ages on sediments from Kow Swamp that are at odds with radiocarbon ages obtained previously for the site. The calibrated 14C ages place the Kow Swamp people in the period 15-9 ka. Our single aliquot OSL ages suggest that they lived around the time of the Last Glacial Maximum (LGM) between 22 and 19 ka. An LGM age for the Kow Swamp people is supported by palaeoenvironmental reconstruction. The shoreline silt, in which most of them were interred, was deposited by high lake levels between 26 and 19 ka. Few robust people were left after 19 ka when a sand lunette formed. Climate change may explain the demise of this unusual genetic population.  相似文献   

4.
张家富 《人类学学报》2022,41(4):712-730
释光测年技术已成为旧石器和古人类遗址,尤其是现代人类遗址,建立年代框架的重要工具之一。这一技术提供了现代人类出现在非洲、亚洲和澳大利亚的最早年代证据。本文简要介绍了释光测年的基本原理,对释光测年的可靠性和上限及所受的影响因素进行了综述。光释光测年的精密度(相对标准误差σ)一般为5%-10%,在理想条件下σ<5%,但是σ>10%的情况也不少见。与大量其他测年方法所获结果的一致性表明,光释光测年技术是可靠的。光释光测年的上限与样品的释光性质及环境剂量率有关,释光可靠年龄最大可达1百万年。对大多数遗址50万年的测年上限是可行的,这个年代范围涵盖了所有的现代人遗址。不同样品或颗粒间的释光性质差异很大,因而它们有不同的测年上限。同一样品中钾长石比石英有更高的测年上限,同一矿物中不同的释光信号对应的测年上限也不同。  相似文献   

5.
Optical dating of dune sands in the northeastern deserts of China   总被引:1,自引:0,他引:1  
Optical dating has been used to obtain the ages of fossil-stabilized sand dunes from four sections in the northeastern deserts of China. Our results indicate that the optically stimulated luminescence ages of the four sections correlate well, even though the samples were collected from different deserts about 600 km apart. Our results also indicate that active dune formation in this region lasted from the Last Glacial Maximum to about 10 ka, and that the warm climate of the Holocene was interrupted by a cold/dry dune formation episode about 3.5-1.7 ka. The Holocene Optimum in this region is between 10 and 3.6 ka, and a later warm/humid dune stabilization phase lasted from at least 1.6 to 1.0 ka. The youngest age on the uppermost sand unit yielded an age of only 40 yr, supporting the previous argument that the existence of modern active eolian sands in the regions with a mean annual precipitation of up to 450 mm is not mainly due to drought, but to extensive land cultivation over historic time. From the luminescence properties of the quartz grains, it is hypothesized that the sands in most of the sections are probably derived from more than one source, with a minor source of quartz having a different thermal history before deposition.  相似文献   

6.
Optically stimulated luminescence (OSL) measurements are reported for single aliquots and single grains of quartz from sedimentary deposits within Cave 13B at Pinnacle Point, South Africa (PP13B). Ages have been obtained for 30 samples from the Middle Stone Age and from sterile geological deposits at the base and top of the sediment sequence. The ages for all the archaeological units have been obtained from single-grain measurements that enable unrepresentative grains to be rejected after they have been scrutinized for their OSL behavior. The shape of the equivalent dose distribution and the degree of spread in equivalent dose for each sample have also been scrutinized for evidence of depositional and post-depositional effects that can influence the accuracy of the age estimates. This study also used the same systematic approach as that used for the dating of the Howieson's Poort and Still Bay in South Africa. This single-grain approach results in more accurate and precise age estimates that place all ages measured and analyzed in this way on a common timescale. Four periods of human occupation have been dated to ~162ka, ~125ka, ~110ka, and ~99-91ka during Marine Isotope Stage (MIS) 6, 5e, 5d, and 5c, respectively. Occupation of the site appears to have occurred at periods of higher sea level and increased aeolian activity, and the cave was ultimately sealed by the accumulation of a large dune ~90ka ago that infilled the cave, but also blanketed the cliff face above the cave, thus preventing further habitation of the site until ~39ka.  相似文献   

7.
Ascertaining the timing of the peopling of Europe, after the first out-of-Africa demographic expansion at the end of the Pliocene, is of great interest to paleoanthropologists. One of the earliest direct evidences for fossil hominins in western Europe comes from an infilled karstic cave site called Gran Dolina at Atapuerca, in a stratum approximately 1.5m below the Brunhes-Matuyama (B-M) geomagnetic boundary (780ka) within lithostratigraphic unit TD6. However, most of the meters of fossil- and tool-bearing strata at Gran Dolina have been difficult to date. Therefore, we applied both thermoluminescence (TL) and infrared-stimulated-luminescence (IRSL) multi-aliquot dating methods to fine-silt fractions from sediment samples within Gran Dolina and the nearby Galería cave site. We also applied these methods to samples from the present-day surface soils on the surrounding limestone hill slopes to test the luminescence-clock-zeroing-by-daylight assumption. Within the uppermost 4m of the cave deposits at Gran Dolina, TL and paired TL and IRSL ages range stratigraphically from 198+/-19ka to 244+/-26ka. Throughout Gran Dolina, all luminescence results are stratigraphically self-consistent and, excepting results from two stratigraphic units, are consistent with prior ESR-U-series ages from progressively deeper strata. Thermoluminescence ages culminate at 960+/-120ka approximately 1m below the 780ka B-M boundary. At Galería, with one exception, TL and IRSL ages range stratigraphically downward from 185+/-26ka to 503+/-95ka at the base of the lowermost surface-inwash facies. These results indicate that TL and (sometimes) IRSL are useful dating tools for karstic inwash sediments older than ca. 100ka, and that a more accurate chronostratigraphic correlation is now possible among the main Atapuerca sites (Gran Dolina, Galería, Sima de los Huesos). Furthermore, the oldest TL age of ca. 960ka from Gran Dolina, consistent with biostratigraphic and paleomagnetic evidence, implies a probable numeric age of 900-950ka for the oldest hominin remains ( approximately 0.8m below the TL sample). This age window suggests a correspondence to Marine Isotope Stage (MIS) 25, a relatively warm and humid interglaciation.  相似文献   

8.
The archaeological deposits at Mumba rockshelter, northern Tanzania, have been excavated for more than 70 years, starting with Margit and Ludwig Köhl-Larsen in the 1930s. The assemblages of Middle Stone Age (MSA) and Later Stone Age (LSA) artefacts collected from this site constitute the type sequences for these cultural phases in East Africa. Despite its archaeological importance, however, the chronology of the site is poorly constrained, despite the application since the 1980s of several dating methods (radiocarbon, uranium-series and amino acid racemisation) to a variety of materials recovered from the deposits. Here, we review these previous chronologies for Mumba and report new ages obtained from optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) measurements on single grains of quartz and multi-grain aliquots of potassium (K) feldspar from the MSA and LSA deposits. Measurements of single grains of quartz allowed the rejection of unrepresentative grains and the application of appropriate statistical models to obtain the most reliable age estimates, while measurements of K-feldspars allowed the chronology to be extended to older deposits. The seven quartz ages and four K-feldspar ages provide improved temporal constraints on the archaeological sequence at Mumba. The deposits associated with the latest Kisele Industry (Bed VI-A) and the earliest Mumba Industry (Bed V) are dated to 63.4 ± 5.7 and 56.9 ± 4.8 ka (thousands of years ago), respectively, thus constraining the time of transition between these two archaeological phases to ∼60 ka. An age of 49.1 ± 4.3 ka has been obtained for the latest deposits associated with the Mumba Industry, which show no evidence for post-depositional mixing and contain ostrich eggshell (OES) beads and abundant microlithics. The Nasera Industry deposits (Bed III) contain large quantities of OES beads and date to 36.8 ± 3.4 ka. We compare the luminescence ages with the previous chronologies for Mumba, and briefly discuss how the revised chronology fits in the context of existing archaeological records and palaeoclimatic reconstructions for East Africa.  相似文献   

9.
The archaeological karstic infill site of Galería Complex, located within the Atapuerca system (Spain), has produced a large faunal and archaeological record (Homo sp. aff. heidelbergensis fossils and Mode II lithic artefacts) belonging to the Middle Pleistocene. Extended-range luminescence dating techniques, namely post-infrared infrared stimulated luminescence (pIR-IR) dating of K-feldspars and thermally transferred optically stimulated luminescence (TT-OSL) dating of individual quartz grains, were applied to fossil-bearing sediments at Galería. The luminescence dating results are in good agreement with published chronologies derived using alternative radiometric dating methods (i.e., ESR and U-series dating of bracketing speleothems and combined ESR/U-series dating of herbivore teeth), as well as biochronology and palaeoenvironmental reconstructions inferred from proxy records (e.g., pollen data). For the majority of samples dated, however, the new luminescence ages are significantly (∼50%) younger than previously published polymineral thermoluminescence (TL) chronologies, suggesting that the latter may have overestimated the true burial age of the Galería deposits. The luminescence ages obtained indicate that the top of the basal sterile sands (GIb) at Galería have an age of up to ∼370 thousand years (ka), while the lowermost sub-unit containing Mode II Acheulean lithics (base of unit GIIa) was deposited during MIS 9 (mean age = 313±14 ka; n = 4). The overlying units GIIb-GIV, which contain the richest archaeopalaeontological remains, were deposited during late MIS 8 or early MIS 7 (∼240 ka). Galería Complex may be correlative with other Middle Pleistocene sites from Atapuerca, such as Gran Dolina level TD10 and unit TE19 from Sima del Elefante, but the lowermost archaeological horizons are ∼100 ka younger than the hominin-bearing clay breccias at the Sima de los Huesos site. Our results suggest that both pIR-IR and single-grain TT-OSL dating are suitable for resolving Middle Pleistocene chronologies for the Sierra de Atapuerca karstic infill sequences.  相似文献   

10.
Since 1991, excavations at Blombos Cave have yielded a well-preserved sample of faunal and cultural material in Middle Stone Age (MSA) levels. The uppermost MSA phase, M1, is dated to c. 75 ka by optically stimulated luminescence (OSL) and thermoluminescence, and the middle M2 phase to a provisional c. 78 ka. Artefacts unusual in a MSA context from these phases include bifacial points, bone tools, engraved ochre and engraved bone. In this paper, we describe forty-one marine tick shell beads recovered from these MSA phases and tick shell beads from Later Stone Age (LSA) levels at Blombos Cave and the Die Kelders site. Thirty-nine shell beads come from the upper M1 phase and two from M2. Morphometric, taphonomic and microscopic analysis of modern assemblages of living and dead tick shell demonstrate that the presence of perforated Nassarius kraussianus shells in the Blombos MSA levels cannot be due to natural processes or accidental transport by humans. The types of perforation seen on the MSA shells are absent on modern accumulations of dead shells and not attributable to post-depositional damage. Their location, size, and microscopic features are similar to those obtained experimentally by piercing the shell wall, through the aperture, with a sharp bone point. Use-wear, recorded on the perforation edge, the outer lip, and the parietal wall of the aperture indicates the shells having being strung and worn. MSA shell beads differ significantly in size, perforation type, wear pattern and shade compared to LSA beads and this eliminates the possibility of mixing across respective levels. Thirty-one beads were found in four groups of five to twelve beads, each group being recovered in a single square or in two adjacent sub-squares during a single excavation day. Within a group, shells display a similar shade, use-wear pattern and perforation size suggesting their provenance from the same beadwork item, lost or disposed during a single event. The likely symbolic significance of these finds suggests levels of cognitively modern behaviour not previously associated with MSA people.  相似文献   

11.
12.
The uppermost Middle Stone Age (MSA) layers at Blombos Cave contain high densities of Still Bay bifacial points. Information from other regional sites places the Still Bay prior to the Howiesons Poort industry, which has been dated at 65-70 ka. The Blombos Cave MSA strata have yielded nine human teeth or dental fragments. Four that were recovered during the 1997-1998 excavations have been published elsewhere. The remaining five were discovered during the 1999-2000 field seasons; these are described here. Three of the new specimens are deciduous teeth, and two are permanent premolar and molar crown fragments. The entire dental sample probably represents at least five and as many as seven individuals. The deciduous teeth from the upper MSA levels are likely to have been exfoliated in the cave. One deciduous tooth and the permanent tooth fragments from the lower MSA levels probably represent three individuals who died in or near the cave. The Blombos Cave premolars preserve horizontal circum-cervical striae suggestive of palliative tooth pick use. Approximately half of the permanent and deciduous crown diameters exceed those of recent Africans; for the remainder, the fossil values fall among modern African sample means. The Blombos Cave tooth crowns tend to be smaller than the majority of penecontemporaneous Neandertal teeth. The morphology of the Blombos Cave di is comparable to MSA homologues from the nearby, and presumably somewhat younger site of Die Kelders Cave 1.  相似文献   

13.
Blombos Cave is well known as an important site for understanding the evolution of symbolically mediated behaviours among Homo sapiens during the Middle Stone Age, and during the Still Bay in particular. The lower part of the archaeological sequence (M3 phase) contains 12 layers dating to MIS 5 with ages ranging from 105 to 90 ka ago (MIS 5c to 5b) that provide new perspectives on the technological behaviour of these early humans. The new data obtained from our extensive technological analysis of the lithic material enriches our currently limited knowledge of this time period in the Cape region. By comparing our results with previously described lithic assemblages from sites south of the Orange River, we draw new insights on the extent of the techno-cultural ties between these sites and the M3 phase at Blombos Cave and highlight the importance of this phase within the Middle Stone Age cultural stratigraphy.  相似文献   

14.
Mineralogy and microbiology of sand from Merzouga (Morocco) were simultaneously characterized, with the purpose of contributing to a better understanding of the geomicrobiology of deserts. In spite of very low measured bacterial biomass, bacterial diversity on each of the five defined mineralogical classes, was found high. An original grain by grain cultivation method enabled to obtain bacterial isolates with an unusually high recovery rate. The results of this study show that the genus Arthrobacter is well adapted to this environment with a preference for grains other than the dominant mineral quartz, and that the genera Chelatococcus and Saccharotrix are strongly attached to the grains.  相似文献   

15.
Stabilized dune fields are common in western Argentina and potentially reflect drought variability in the Late Quaternary. This study focussed on deciphering geomorphic and stratigraphic record of three vegetated dune fields from east to west, San Luis, Médanos Negros and Médanos Grandes, with a mean annual precipitation from ∼ 700 to 91 mm. Optically stimulated luminescence single-aliquot regeneration protocols yield ages on eolian quartz grains, constraining depositional events. The San Luis dune field, the wettest area, exhibits evidence for repeated activation during the last glaciation, ca. 33-20 ka, generally coincident with regional loess deposition These dunes were locally reformed in the past 100 years which is apparently coincident with intensified agrarian use and drying in the late 19th and early 20th century. The two driest and western-most dune fields, Médanos Negros and Médanos Grandes, show reactivation at ca. 2.5 ka 0.9 and 0.5 ka; and ca. 4.3-4, 2.1 and 0.6-0.4 ka, respectively. Eolian depositional events at ca. 2.5-2.1 ka and 0.6-0.4 ka may be coeval for Médanos Grandes and Negros dune fields. Sustained drought conditions conducive for eolian activity is associated with warmer sea surface temperatures in the South Atlantic, a weakened South American Convergent Zone and a dispersed and southeasterly flow of tropical moisture from the Low Level Chaco Jet. This nascent analysis indicates drought variability beyond historic observations with potentially at least four dune reactivation events in the past ca. 4.5 ka.  相似文献   

16.
Seven human teeth from Tabun Cave, Israel, curated at the Natural History Museum London since 1955, are of uncertain provenance and identity. They are all from the upper dentition, without duplications, and are characterized by a similar preservation. The Catalogue of Fossil Hominids (1975) suggested that they might have derived from Tabun Layer A (Bronze Age to Recent). However, one of us (AC) noted some distinctive features of these teeth that warranted further study. They are here assigned to a single individual, Tabun BC7. Their morphology and metrics were then compared with the frequency of Late Pleistocene and Early Holocene groups from Europe, North Africa and Middle East. A fragment of the right M3 crown of Tabun BC7 was removed for ESR and U-analysis, and it was determined that only samples from Layer B have similar dose values. Using the sediment dose values of layer B, preliminary age estimates of 82 +/- 14 ka (early U-uptake) and 92+/-18 ka (linear uptake) were obtained. U-series disequilibrium determined from other samples attributed to Layer B resulted in a U-uptake history close to linear uptake, giving a very comparable age estimate of 90(+30)(-16) ka. The dose value previously obtained on an enamel fragment from the Tabun C1 dentition is nearly double the value measured for BC7, and tentative age estimates for C1 were in the range of 143+/-37 ka. However, due to uncertainties in the exact provenance of the human fossils, we cannot confirm that C1 is older than the new tooth sampled here, and both C1 and BC7 can be attributed to Layer B on chronological grounds. On the basis of chronology, dental morphology and metrics, the specimen named Tabun BC7 was identified as a probable Neanderthal.  相似文献   

17.
Two fragments of a hominin tooth (Australopithecus robustus) and two bovid teeth from the Hanging Remnant of the Swartkrans Formation were analysed with ESR. Research was complicated by the fact that the samples came from a curated collection and their precise provenance is unknown. The environmental dose rate was reconstructed by a series of in situ gamma spectrometric measurements and elemental analyses of a range of sediment samples. U-series isotopic analyses indicated that each of the teeth had a significantly different uranium uptake history, rendering the assumptive early U-uptake and linear U-uptake models ineffective. ESR and U-series data were combined to calculate open system ages, resulting in a best estimate of 1630+/-160 ka for the Hanging Remnant. An open-system model which provides the maximum age for given U-series and ESR measurements yielded an estimate of about 2100 ka.Two bovid teeth from Member 2, previously estimated to be between 1.0 and 2.0 Ma, yielded age estimates of between about 100 and 200 ka. No known geochemical processes are likely to explain this severe age underestimation. We conclude that these samples are of Middle to Upper Pleistocene age and their presence in Member 2 was either due to reworking or inadequate stratigraphical discrimination of these deposits.  相似文献   

18.
The Xiaogushan cave site is one of the most important prehistoric sites in North China. The stone and bone artifacts found in the cave are similar to European contemporaneous artifacts. Cave deposits consist of five layers that have been dated from 46,353 ± 1179 to 4229 ± 135 cal. yr BP, using radiocarbon dating techniques on charcoal and bone samples collected from Layers 2-5. In this paper, optically stimulated luminescence (OSL) techniques were applied to date six samples taken from Layers 1-3. The luminescence properties of the fine-grained and coarse-grained quartz extracts indicate that the materials are suitable for OSL dating using a single-aliquot regeneration-dose (SAR) protocol. The OSL ages obtained are broadly consistent with the stratigraphy and the associated calibrated radiocarbon ages. The dating results show that the cave was first occupied by humans about 70 ka. The human occupation of the cave may be related to climate change. An occupation hiatus is inferred to between ∼17 to ∼10 ka. The stone and bone artifacts found in Layers 2 and 3 may indicate the Middle to Upper Paleolithic transitions in the region.  相似文献   

19.
S Gibson  C Y Jung  M Takahashi  J Lenard 《Biochemistry》1986,25(20):6264-6268
The size of the functional units responsible for several activities carried out by the influenza virus envelope glycoproteins was determined by radiation inactivation analysis. Neuraminidase activity, which resides in the glycoprotein NA, was inactivated exponentially with an increasing radiation dose, yielding a target size of 94 +/- 5 kilodaltons (kDa), in reasonable agreement with that of the disulfide-bonded dimer (120 kDa). All the other activities studied are properties of the HA glycoprotein and were normalized to the known molecular weight of the neuraminidase dimer. Virus-induced fusion activity was measured by two phospholipid dilution assays: relief of energy transfer between N-(7-nitro-2,1,3-benzoxadiazol-4-yl)dipalmitoyl-L-alpha- phosphatidylethanolamine (N-NBD-PE) and N-(lissamine rhodamine B sulfonyl)-dioleoyl-L-alpha-phosphatidylethanolamine (N-Rh-PE) in target liposomes and relief of self-quenching of N-Rh-PE in target liposomes. Radiation inactivation of fusion activity proceeded exponentially with radiation dose, yielding normalized target sizes of 68 +/- 6 kDa by assay i and 70 +/- 4 kDa by assay ii. These values are close to the molecular weight of a single disulfide-bonded (HA1 + HA2) unit (75 kDa), the "monomer" of the HA trimer. A single monomer is thus inactivated by each radiation event, and each monomer (or some part of it) constitutes a minimal functional unit capable of mediating fusion. Virus-induced leakage of calcein from target liposomes and virus-induced leakage of hemoglobin from erythrocytes (hemolysis) both showed more complex inactivation behavior: a pronounced shoulder was present in both inactivation curves, followed by a steep drop in activity at higher radiation levels.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

20.
This paper presents TL age estimates of Pleistocene raised marine terraces from southern Calabria (southern Italy). It focuses on the dating of last interglacial shallow-marine sand deposits, including several Tyrrhenian key reference deposits whose stratigraphic assignment is based on biostratigraphic evidence (presence of a Strombus bubonius fauna) and geochronometric data (amino-acid data calibrated with U/Th dates on coral). The TL age estimates are obtained on alkali feldspar coarse grains using their blue TL emission. They are in good agreement with the IR-OSL age estimates obtained on the same feldspar samples. Our feldspar TL method is tested on two Tyrrhenian key reference sites, Ravagnese and Bovetto, in the Reggio di Calabria area. Their measured TL age estimates (97 ± 11 ka and 100 ± 10 ka) are lower than their estimated geological age (i.e. Oxygen Isotope Substage 5e). The correction for long-term fading suggested by Mejdahl (1988), is tested on these two samples using a lifetime of 446 ka as estimated from both Calabrian and Miocene sand collected within the same area. This correction would yield preliminary TL ages (116 ± 13 ka and 116 ± 12 ka) that are in better agreement with the expected geological age. The application of our TL method to paleoshorelines lying below the Tyrrhenian reference shoreline of Ravagnese-Bovetto, yields stratigraphically consistent TL age estimates. The TL method is also applied to two supposedly pre-last interglacial paleoshorelines which are geomorphologically older than the Tyrrhenian reference shorelines. They remain however chronologically undifferentiated, both by the TL and the amino-acid methods. Finally, the preliminary feldspar TL results obtained on the Miocene and the Calabrian sand deposits (> 1 Ma), suggest that our feldspar TL method is limited, in the SW Calabrian area, to about 200 ka.  相似文献   

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