Distribution by Scientific Domains
Distribution within Earth and Environmental Science

Kinds of Dating

  • absolute dating
  • age dating
  • ar dating
  • isotopic dating
  • luminescence dating
  • molecular dating
  • osl dating
  • precise dating
  • radiocarbon dating
  • u-pb dating
  • zircon dating

  • Terms modified by Dating

  • dating methods
  • dating partner
  • dating relationships
  • dating techniques
  • dating violence

  • Selected Abstracts


    S.N. Ehrenberg
    Eight samples of brachiopod shell material have been analyzed for their strontium isotope composition in order to more accurately date Lower to Upper Permian siliceous biogenic strata of Spitsbergen (Kapp Starostin Formation) and the southern Barents Sea (Rřye Formation). The results are interpreted as showing a mid-Artinskian age for the basal Vřringen Member of the Kapp Starostin Formation and a range of late Artinskian to Roadian for the overlying part of this unit. The upper part of the Rřye Formation yields ages in the range Roadian to Wuchiapingian. These results are consistent with available biostratigraphic data and confirm the potential of strontium isotope stratigraphy for developing a more accurate chronology of the widespread spiculite deposits that characterize the northern margin of Pangea in late-Early Permian to Late Permian time and which constitute a potential target for petroleum exploration. [source]


    ACTA ARCHAEOLOGICA, Issue 1 2006
    Article first published online: 31 JAN 200
    No abstract is available for this article. [source]


    ACTA ARCHAEOLOGICA, Issue 1 2003
    Kalle Sognnes
    First page of article [source]


    ARCHAEOMETRY, Issue 4 2010
    T. De TORRES
    The age of Neanderthal remains and associated sediments from El Sidrón cave has been obtained through different dating methods (14CAMS, U/TH, OSL, ESR and AAR) and samples (charcoal debris, bone, tooth dentine, stalagmitic flowstone, carbonate-rich sediments, sedimentary quartz grains, tooth enamel and land snail shells). Detrital Th contamination rendered Th/U dating analyses of flowstone unreliable. Recent 14C contamination produced spurious age-values from charcoal samples as well as from inadequately pretreated tooth samples. Most consistent 14C dates are grouped into two series: one between 35 and 40 ka and the other between 48 and 49 ka. Most ESR and AAR samples yielded concordant ages, ranging between 39 and 45 ka; OSL dating results permitted adequate bracketing of the sedimentary layer that contained the human remains. Our results emphasize the value of multi-dating approaches for the establishment of reliable chronologies of human remains. [source]


    ARCHAEOMETRY, Issue 4 2009
    In 2005, sherds of a special type of ancient Longquan celadon ware were excavated at Maojiawan, in the city of Beijing, China. Although archaeologists agree that these sherds were fired in the period between the Yuan and Ming Dynasties, their specific date is unclear. In order to solve this problem, five other groups of ancient Longquan celadon sherds of known date were selected as reference samples. The elemental body composition of all the sherds was determined by Instrumental Neutron Activation Analysis (INAA). Using the same principles as in provenance research, pattern recognition methods were used to build classification functions to specify the date of the unknown sherds. After analysing the experimental data by discriminant analysis, three classification functions were built. All the unknown sherds were classified as Ming Dynasty. This prediction is well in accordance with the fact that these sherds are similar to other Longquan Ming celadon, and so they should be fired in the same dynasty. This also verified the judgement of the Beijing Institute of Cultural Relics. [source]


    ARCHAEOMETRY, Issue 2 2009
    A. LODGE
    We introduce a new approach to producing secular variation curves for archaeomagnetic dating, using global geomagnetic field modelling techniques. Using published palaeosecular variation curves for five European locations as input, and a previous global model for regularization, we produce a model for the period ad 0,1900, which reproduces the input curves within their 95% confidence intervals, and successfully fits data from other regions in Europe. Our global model performs as well as a previous regional model, but additionally ensures consistency with physical constraints. We show that the curves currently used for dating are not mutually consistent, and therefore that in the future this new approach will provide more reliable curves for archaeomagnetic dating. [source]


    ARCHAEOMETRY, Issue 4 2007
    Fired clay brick samples, obtained from a group of seven high-status late-medieval and post-medieval buildings in England ranging in age from c. ad 1390 to 1740, were dated by the luminescence method using an optically stimulated luminescence (OSL) technique. The results obtained indicate that, when applied to quartz extracted from brick, the technique is capable of producing dates that are in consistently good agreement with independent dating evidence for the buildings. For six samples taken from a group of four dating ,control' buildings the mean difference between the central values of luminescence and assigned ages was 5 ± 10 years (SD, n = 6). The methodology used is appropriate for application to other standing buildings in other temporal and geographic regions, and may be used with confidence where conventional dating methods are less certain. The study also examines the luminescence characteristics of quartz and the characteristics of the lithogenic radionuclides in brick samples and identifies various aspects related to the assessment of experimental uncertainty in testing the reliability of the method. [source]

    Dating young geomorphic surfaces using age of colonizing Douglas fir in southwestern Washington and northwestern Oregon, USA,

    Thomas C. Pierson
    Abstract Dating of dynamic, young (<500 years) geomorphic landforms, particularly volcanofluvial features, requires higher precision than is possible with radiocarbon dating. Minimum ages of recently created landforms have long been obtained from tree-ring ages of the oldest trees growing on new surfaces. But to estimate the year of landform creation requires that two time corrections be added to tree ages obtained from increment cores: (1) the time interval between stabilization of the new landform surface and germination of the sampled trees (germination lag time or GLT); and (2) the interval between seedling germination and growth to sampling height, if the trees are not cored at ground level. The sum of these two time intervals is the colonization time gap (CTG). Such time corrections have been needed for more precise dating of terraces and floodplains in lowland river valleys in the Cascade Range, where significant eruption-induced lateral shifting and vertical aggradation of channels can occur over years to decades, and where timing of such geomorphic changes can be critical to emergency planning. Earliest colonizing Douglas fir (Pseudotsuga menziesii) were sampled for tree-ring dating at eight sites on lowland (<750 m a.s.l.), recently formed surfaces of known age near three Cascade volcanoes , Mount Rainier, Mount St. Helens and Mount Hood , in southwestern Washington and northwestern Oregon. Increment cores or stem sections were taken at breast height and, where possible, at ground level from the largest, oldest-looking trees at each study site. At least ten trees were sampled at each site unless the total of early colonizers was less. Results indicate that a correction of four years should be used for GLT and 10 years for CTG if the single largest (and presumed oldest) Douglas fir growing on a surface of unknown age is sampled. This approach would have a potential error of up to 20 years. Error can be reduced by sampling the five largest Douglas fir instead of the single largest. A GLT correction of 5 years should be added to the mean ring-count age of the five largest trees growing on the surface being dated, if the trees are cored at ground level. This correction would have an approximate error of ±5 years. If the trees are cored at about 1·4 m above the ground surface (breast height), a CTG correction of 11 years should be added to the mean age of the five sampled trees (with an error of about ±7 years). Published in 2006 by John Wiley & Sons, Ltd. [source]

    The Perils of the Back Seat: Date Rape, Race and Gender in 1950s America

    GENDER & HISTORY, Issue 1 2008
    Lisa Lindquist Dorr
    Dating among white American teenagers in the 1950s caused parents considerable concern, as it represented disturbing developments in sexual expectations. While the rhetoric surrounding marriage celebrated traditional gender roles and monogamy, Americans bemoaned social and moral decay, caused in part by women's encroachment on male prerogatives. Sexual experience for boys increasingly became a defining gender characteristic and a means of achieving manhood as well. Ideas about proper marital norms and studies of dating practices among young people naturalised male aggression as proof of masculinity, which made girls, even ,respectable ones', vulnerable to violence from their dates. As teens' acceptance of going steady became more widespread, older racialised narratives of sexual danger evolved to incorporate new dating trends. Whereas American, and especially southern white, women knew the dangers of the supposed ,black beast rapist', they learnt during the 1950s that a special danger could confront them in the back seat of cars, despite the presence of their white, male date. Even with a white protector, white women remained vulnerable to violence on dates, whether from black men or from their white date. As dating conventions loosened, white women found that that the perils of the back seat only increased. [source]

    Archaeological evidence for destructive earthquakes in Sicily between 400 B.C. and A.D. 600

    Carla Bottari
    A systematic archaeoseismological study indicates that at least three earthquakes occurred between 400 B.C. and A.D. 600, causing destruction to numerous ancient monuments in Sicily. Evidence for these earthquakes comes from the collapse style of buildings (toppled walls, column drums in a domino-style arrangement, directional collapses, etc.), and the exclusion of other likely causes for such effects. Dating of inferred earthquakes is based on coins (accurate to within 5,10 years), pottery (accurate to within 50,200 years), and other artifacts. The oldest documented earthquake occurred between 370 and 300 B.C. and caused the collapse of two Greek temples in Selinunte. This otherwise poorly documented event was probably also the cause of extensive destruction in northeastern Sicily in the first century A.D. Destruction of some sites may be assigned to an earthquake that occurred between 360 and 374 and correlates with the A.D. 365 seismic sequence known from historical sources. This study covers a wider region and provides a more precise dating of earthquakes than previous studies. Although it focuses on a certain period (4th,3rd centuries B.C., 4th,7th centuries A.D.), it indicates that the period before A.D. 1000 is not a period of seismic quiescence in Sicily as was previously believed, but to a period characterized by strong and destructive earthquakes. © 2009 Wiley Periodicals, Inc. [source]

    Prehistoric gold markers and environmental change: A two-age system for standing stones in western Ireland

    K.R. Moore
    The Murrisk Peninsula in southwest County Mayo is a major target for gold exploration in Ireland. The most productive areas include the Cregganbaun Shear Zone and Cregganbaun Quartzite Belt on Croagh Patrick, both geologically related to Iapetus closure, and gold is concentrated in alluvial deposits of river systems draining these areas. A comparison of gold occurrences with the location of prehistoric stone monuments reveals that simple standing-stone monuments, though isolated from other monument types, correlate with alluvial gold. South of the Murrisk Peninsula in Connemara, isolated standing stones are associated with a wide range of mineral resources and with other monuments. Dating of the stones relative to blanket-bog expansion and coastal landform changes indicates that standing stones were raised as markers of gold placer deposits before a climatic deterioration at 1200 B.C. Late Bronze Age monuments with a ceremonial purpose are more complex and include stone alignments. © 2006 Wiley Periodicals, Inc. [source]

    On Radiocarbon Dating of Ground Water

    GROUND WATER, Issue 6 2000
    Chen Zhu
    No abstract is available for this article. [source]

    An Early Bronze Age Logboat from Degersee, Southern Germany

    Martin Mainberger
    In 2004 the remains of a logboat were discovered in Degersee, a small lake near Lake Constance, southern Germany. Dating to the beginning of the 2nd millennium BC, it is an important find from a period with scarce archaeological evidence and only a few previously-known logboats. The vessel was situated in lake sediment and documented in situ. Our investigations can be linked to palaeo-environmental studies carried out at Degersee and adjacent lakes, and to palaeo-climatic research in the northern Alpine region. After investigation by underwater archaeologists the boat was moved to a sheltered place in deeper water. © 2008 The Author [source]

    Intimate Partner Violence in Young Adult Dating, Cohabitating, and Married Drinking Partnerships

    Jacquelyn D. Wiersma
    Using data from the National Longitudinal Study of Adolescent Health, this study examined intimate partner violence (IPV) and drinking partnerships in 741 young adults in male-female dating, cohabitating, and married relationships. Cluster analyses revealed four similar kinds of drinking partnerships: (a) congruent light and infrequent, (b) discrepant male heavy and frequent, (c) discrepant female heavy and infrequent, and (d) congruent moderate/heavy-frequent drinkers. Overall, there were no significant main effect differences across relationship type and clusters. The type of relationship and the type of drinking partnership interacted with contexts examined (i.e., type of violence severity, gender, and whether the violence was perpetration or victimization). Given the severity of IPV in couple relationships, additional empirical attention to drinking partnerships is warranted. [source]

    Biostratigraphic and aminostratigraphic constraints on the age of the Middle Pleistocene glacial succession in north Norfolk, UK,

    Richard C. Preece
    Abstract Considerable debate surrounds the age of the Middle Pleistocene glacial succession in East Anglia following some recent stratigraphical reinterpretations. Resolution of the stratigraphy here is important since it not only concerns the glacial history of the region but also has a bearing on our understanding of the earliest human occupation of north-western Europe. The orthodox consensus that all the tills were emplaced during the Anglian (Marine Isotope Stage (MIS) 12) has recently been challenged by a view assigning each major till to a different glacial stage, before, during and after MIS 12. Between Trimingham and Sidestrand on the north Norfolk coast, datable organic sediments occur immediately below and above the glacial succession. The oldest glacial deposit (Happisburgh Till) directly overlies the ,Sidestrand Unio -bed', here defined as the Sidestrand Hall Member of the Cromer Forest-bed Formation. Dating of these sediments therefore has a bearing on the maximum age of the glacial sequence. This paper reviews the palaeobotany and describes the faunal assemblages recovered from the Sidestrand Unio -bed, which accumulated in a fluvial environment in a fully temperate climate with regional deciduous woodland. There are indications from the ostracods for weakly brackish conditions. Significant differences are apparent between the Sidestrand assemblages and those from West Runton, the type site of the Cromerian Stage. These differences do not result from contrasting facies or taphonomy but reflect warmer palaeotemperatures at Sidestrand and a much younger age. This conclusion is suggested by the higher proportion of thermophiles at Sidestrand and the occurrence of a water vole with unrooted molars (Arvicola) rather than its ancestor Mimomyssavini with rooted molars. Amino acid racemisation data also indicate that Sidestrand is significantly younger than West Runton. These data further highlight the stratigraphical complexity of the ,Cromerian Complex' and support the conventional view that the Happisburgh Till was emplaced during the Anglian rather than the recently advanced view that it dates from MIS 16. Moreover, new evidence from the Trimingham lake bed (Sidestrand Cliff Formation) above the youngest glacial outwash sediments (Briton's Lane Formation) indicates that they also accumulated during a Middle Pleistocene interglacial , probably MIS 11. All of this evidence is consistent with a short chronology placing the glacial deposits within MIS 12, rather than invoking multiple episodes of glaciation envisaged in the ,new glacial stratigraphy' during MIS 16, 12, 10 and 6. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Mixed-Gender Groups, Dating, and Romantic Relationships in Early Adolescence

    Jennifer Connolly
    This study examined dating-stage and developmental-contextual models of romantic relationships during early adolescence. Same-gender friendships, affiliation with mixed-gender groups, dating, and romantic relationships were investigated in a sample of 1,284 young adolescents of diverse ethnocultural backgrounds. Data were collected cross-sectionally in Grades 5 through 8, as well as longitudinally in the fall and spring of an academic year. Consistent with a stage model, affiliation with mixed-gender groups and dating were qualitatively distinct activities that were sequentially organized and facilitated the progression from same-gender friendships to dyadic romantic relationships. The results also provide insights on how the developmental context may alter stage pathways: Dating activities were incorporated with mixed-gender affiliations, group-based romantic stages showed more stability than other stages, and the ethnocultural context influenced romantic timing. Finally, results indicated that participation in romantic activities heightened adolescents' future interest in having a romantic relationship. [source]

    Sacral nerve stimulation for voiding dysfunction: One institution's 11-year experience,

    Suzette E. Sutherland
    Abstract Aim The purpose of this study was to review our institution's 11-year experience with SNS for the treatment of refractory voiding dysfunction. Dating back to 1993, it covers a span of time which describes the evolution of SNS as it includes PNE trials, non-tined (bone-anchored or fascial-anchored) leads, percutaneous tined leads with two-staged procedures, and even percutaneous pudendal trials. Methods A retrospective review was performed on SNS patients who received an implantable pulse generator (IPG) in our practice from 12/1993 to 12/2004. After Institutional Review Board approval, consents for chart review were obtained from 104 patients, representing 44% of this neuromodulatory patient population. Results Of our population, 87% were female and 13% were male. Average age at implant was 50 years,±,13.4 years. Duration of symptoms before implantation was 116 months (range 9,600 months). Eighty percent were implanted for a predominant complaint of urinary urgency and frequency (U/F). Overall, 22% had U/F only, 38% had concomitant urge incontinence (UI), and 20% had concomitant mixed incontinence (MI). Twenty percent were treated for non-obstructive urinary retention (UR), with half of these associated with a neurogenic etiology. Additionally, 46.2% had pelvic pain, 58.6% had bowel complaints, and 51% reported sexual dysfunction. In patients with U/F, mean voiding parameters as described by pre-implant voiding diaries revealed the following: 12.4 (±5.1) voids per 24 hr; 2.3 (±1.8) voids per night; 5.0 (±4.7) leaks per 24 hr; and 2.3 (±2.6) pads per 24 hr. Statistically significant improvements post-implantation were noted with mean decreases in the following: 4.3 voids per 24 hr; 1.0 void per night; 4.4 leaks per 24 hr; and 2.3 pads per 24 hr (all P,<,0.05). In the UR group a statistically significant improvement post-implantation was noted only in voids per night, with a mean decrease of 0.8 (P,<,0.05). With a mean follow up of 22 months (range 3,162 months), sustained subjective improvement was >50%, >80%, and >90% in 69%, 50%, and 35% of patients, respectively. By quality of life survey, 60.5% of patients were satisfied and 16.1% were dissatisfied with current urinary symptoms. Only 13% (14 patients) abandoned therapy, making up a significant portion of those dissatisfied with current urinary symptoms. Good overall lead durability was seen (mean 22 months, range 1,121 months), with the first successful lead proving to be the most durable (mean 28 months, range 1.4,120 months). Lead durability decreased progressively with subsequent trials. Overall, 53% of patients experienced at least one reportable event (RE) attributable to either lead or IPG. A total of 126 REs were noted, with 97% mild-to-moderate in severity. REs included lack of efficacy, loss of efficacy, infection, hematoma/seroma, migration, pain, undesirable change in sensation, and device malfunction. In this population, 47.1% of leads were tined while 52.9% were non-tined. Tined leads had an overall lower RE rate as compared to non-tined leads: 28% and 73%, respectively. Conclusions SNS is an effective method for treating certain types of voiding dysfunction. Although 53% of patients experienced at least one RE, 97% were mild-to-moderate and did not appear to affect the continued use of this therapy. With improved technology, such as percutaneous tined leads, the RE rate is decreasing. Further analyses of subsets of this population are currently underway. Neurourol. Urodynam. © 2006 Wiley-Liss, Inc. [source]

    Crannogs and Island Duns: Classification, Dating and Function

    D. W. Harding
    A recent paper, Islets through Time (OJA 17, 2, 227--44), by Jon Henderson highlighted the fact that the majority of dated crannogs were occupied in the later prehistoric or early historic period, and offered a new classification of artificial islets. This paper addresses consequential issues of definition and classification and urges that artificial islets, whether classed hitherto as crannogs or island duns, should be seen as complementary elements within a spectrum of settlement types, in particular for the Early Iron Age and the early historic periods. Comparison shows that studies of crannogs and their land-based counterparts have faced similar problems of interpretation and that typological compartmentalization has acted to the detriment of a proper understanding of both. [source]

    Dating and Nondating Relationships Among Sexually Active Adolescents Are Often Surprisingly Similar

    H. Ball
    No abstract is available for this article. [source]

    Hooking Up: Sex, Dating, and Relationships on Campus

    Daniel Farr
    No abstract is available for this article. [source]

    40Ar/39Ar Dating of Xuebaoding Granite in the Songpan-Garzę Orogenic Belt, Southwest China, and its Geological Significance

    Yan LIU
    Abstract: Thus far, our understanding of the emplacement of Xuebaoding granite and the occurrence and evolution of the Songpan-Garzę Orogenic Belt has been complicated by differing age spectra results. Therefore, in this study, the 40Ar/39Ar and sensitive high resolution ion micro-probe (SHRIMP) U-Pb dating methods were both used and the results compared, particularly with respect to dating data for Pankou and Pukouling granites from Xuebaoding, to establish ages that are close to the real emplacements. The results of SHRIMP U-Pb dating for zircon showed a high amount of U, but a very low value for Th/U. The high U amount, coupled with characteristics of inclusions in zircons, indicates that Xuebaoding granites are not suitable for U-Pb dating. Therefore, muscovite in the same granite samples was selected for 40Ar/39Ar dating. The 40Ar/39Ar age spectrum obtained on bulk muscovite from Pukouling granite in the Xuebaoding, gave a plateau age of 200.1±1.2 Ma and an inverse isochron age of 200.6±1.2 Ma. The 40Ar/39Ar age spectrum obtained on bulk muscovite from Pankou granite in the Xuebaoding gave another plateau age of 193.4± 1.1 Ma and an inverse isochron age of 193.7±1.1 Ma. The 40Ar/39Ar intercept of 277.0±23.4 (2,) was very close to the air ratio, indicating that no apparent excess argon contamination was present These age dating spectra indicate that both granites were emplaced at 200.6±1.3 Ma and 193.7±1.1 Ma, respectively. Through comparison of both dating methods and their results, we can conclude that it is feasible that the muscovite in the granite bearing high U could be used for 40Ar/39Ar dating without extra Ar. Based on this evidence, as well as the geological characteristics of the Xuebaoding W-Sn-Be deposit and petrology of granites, it can be concluded that the material origin of the Xuebaoding W-Sn-Be deposit might partially originate from the Xuebaoding granite group emplacement at about 200 Ma. Moreover, compared with other granites and deposits distributed in various positions in the Songpan-Garzę Orogenic Belt, the Xuebaoding emplacement ages further show that the main rare metal deposits and granites in peripheral regions occurred earlier than those in the inner Songpan-Garzę. Therefore, 40Ar/39Ar dating of Xuebaoding granite will lay a solid foundation for studying the occurrence and evolution of granite and rare earth element deposits in the Songpan-Garzę Orogenic Belt. [source]

    Late Quaternary history of the Kap Mackenzie area, northeast Greenland

    BOREAS, Issue 3 2010
    Wagner, B., Bennike, O., Cremer, H. & Klug, M. 2010: Late Quaternary history of the Kap Mackenzie area, northeast Greenland. Boreas, Vol. 39, pp. 492,504. 10.1111/j.1502-3885.2010.00148.x. ISSN 0300-9483. The Kap Mackenzie area on the outer coast of northeast Greenland was glaciated during the last glacial stage, and pre-Holocene shell material was brought to the area. Dating of marine shells indicates that deglaciation occurred in the earliest Holocene, before 10 800 cal. a BP. The marine limit is around 53 m a.s.l. In the wake of the deglaciation, a glaciomarine fauna characterized the area, but after c. one millennium a more species-rich marine fauna took over. This fauna included Mytilus edulis and Mysella sovaliki, which do not live in the region at present; the latter is new to the Holocene fauna of northeast Greenland. The oldest M. edulis sample is dated to c. 9500 cal. a BP, which is the earliest date for the species from the region and indicates that the Holocene thermal maximum began earlier in the region than previously documented. This is supported by driftwood dated to c. 9650 cal. a BP, which is the earliest driftwood date so far from northeastern Greenland and implies that the coastal area was at least partly free of sea ice in summer. As indicated by former studies, the Storegga tsunami hit the Kap Mackenzie area at c. 8100 cal. a BP. Loon Lake, at 18 m a.s.l., was isolated from the sea at c. 6200 cal. a BP, which is distinctly later than expected from existing relative sea-level curves for the region. [source]

    Towards a chronology of the Late Pleistocene in the northern Alpine Foreland

    BOREAS, Issue 3 2004
    Dating results from terrestrial records in the northern foreland of the Alps have been compiled in order to establish an independent chronostratigraphy for the climate history of this region. U/Th dates of peat deposited during the final phase of the Last Interglacial indicate that it lasted until at least c. 115 000 yr ago. The Early Würmian started with a period of severe cold climate causing a substitution of forest by tundra-like vegetation. It is assumed that during this period glaciers advanced to the margin of the foreland of at least the Western Alps. Sediments attributed to this glaciation are dated to about 103 000 yr. Three subsequent interstadials, all characterized by coniferous forest, were interrupted by cold stadials with steppe to tundra-like vegetation. The first interstadial is dated to about 95 000 yr. There is evidence for an interstadial with open coniferous woodland and three phases of steppe vegetation during the Middle Würmian, between c. 50000 and 30 000 yr ago. The last glaciation of the Alpine Foreland reached its maximum extension between 24 000 and 21 500 yr and glaciers rapidly collapsed before ,17 500 yr ago. A series of minor re-advances during the Lateglacial is reported from within the Alps, but the glaciers barely reached the main Alpine valleys during this time. The last of these advances formed the Egesen moraine and occurred at about 11 800 yr ago during the Younger Dryas. [source]

    Chemical U-Th-Pb Monazite Dating of Deformations versus Pluton Emplacement and the Proterozoic History of the Arkansas River Region, Colorado, USA

    Hui CAO
    Abstract: Five lengthy periods involving multiple phases of cordierite and andalusite growth were revealed by detailed studies of foliation inflection/intersection axes (FIA) preserved in porphyroblasts in schists from the Arkansas River region in Colorado, USA. The regionally consistent character of the succession of five different FIA trends enabled the relative timing of each FIA with respect to the next to be determined. The FIA succession from first to last is: FIA 1 trending W-E, FIA 2 trending SSW-NNE, FIA 3 trending NNW-SSE, FIA 4 trending NW-SE and FIA 5 trending SW-NE. For four of the FIA sets, samples were found containing monazite grains preserved as inclusions. These were dated on an electron microprobe. The ages obtained concur exactly with the FIA succession, with FIA 1 at 1506 ± 15 Ma, FIA 2 at 1467 ± 23 Ma, FIA 3 at 1425 ± 18 Ma, FIA 4 not dated and FIA 5 at 1366 ± 20 Ma. These ages are directly reflected in a succession of plutons in the surrounding region dated by other isotopic approaches, suggesting that deformation, metamorphism and pluton emplacement occurred together episodically, but effectively continuously, for some 140 Ma. [source]

    40Ar- 39Ar Dating of Albite and Phlogopite from Porphyry Iron Deposits in the Ningwu Basin in East-Central China and Its Significance

    YU Jinjie
    Abstract,40Ar- 39Ar dating of albite from the Meishan and Taocun iron deposits yields plateau ages of 122.90±0.16 Ma and 124.89±0.30 Ma, and isochron ages of 122.60±0.16 Ma and 124.90±0.29 Ma, respectively. Phlogopite from the Zhongshan-Gushan ore field has a plateau age of 126.7±0.17 Ma and an isochron age of 127.21±1.63 Ma. Analysis of regional geodynamic evolution of the middle-lower Yangtze River region suggests that the porphyry iron deposits were formed as a result of large-scale lithosphere delamination and strong sinistral strike-slip movement of the Tancheng-Lujiang fault zone. The copper, molybdenum and gold deposit system in the middle-lower Yangtze River region was formed during the stress transition period of the eastern China continent. [source]

    U-Pb SHRIMP Dating of Zircon from Quartz Veins of the Yangshan Gold Deposit in Gansu Province and Its Geological Significance

    QI Jinzhong
    Abstract, The Yangshan gold deposit is a super-large fine-grained disseminated gold deposit located in southern Gansu Province. Its metallogenic age has been determined by using the cathodoluminescence image and ion probe U-Pb dating techniques. It is found that zircons from quartz veinlet of the fine-grained disseminated gold ore show characters of magmatic origin with prism idiomorphism, oscillatory zoning and dominant Th/U ratios of 0.5,1.5. Three main populations of zircons are obtained, giving average 206Pb/238U ages of 197.6±1.7 Ma, 126.9±3.2 Ma and 51.2±1.3 Ma respectively. The first age corresponds to the K-Ar age of the plagiogranite dike, while the latter two ages indicate that buried Cretaceous and Tertiary intrusives exist in the orefield, suggesting that the Yangshan gold deposit was genetically related to the three magmatic hydrothermal activities. By contrast, zircons from coarse gold-bearing quartz vein in the mining area are much older than the host rock, indicating that the vein was formed earlier and was not contaminated by later magmatic fluids. It is concluded that the coupling of multiperiodic hydrothermal activities in the mining area has contributed a lot to mineralization of the Yangshan gold deposit. [source]

    40Ar/39Ar Dating of Deformation Events and Reconstruction of Exhumation of Ultrahigh-Pressure Metamorphic Rocks in Donghai, East China

    LI Jinyi
    Abstract Recent investigations reveal that the ultrahigh-pressure metamorphic (UHPM) rocks in the Donghai region of East China underwent ductile and transitional ductile-brittle structural events during their exhumation. The earlier ductile deformation took place under the condition of amphibolite facies and the later transitional ductile-brittle deformation under the condition of greenschist facies. The hanging walls moved southeastward during both of these two events. The 40Ar/39Ar dating of muscovites from muscovite-plagioclase schists in the Haizhou phosphorous mine, which are structurally overlain by UHPM rocks, yields a plateau age of 218.0±2.9 Ma and isochron age of 219.8Ma, indicating that the earlier event of the ampibolite-facies deformation probably took place about 220 Ma ago. The 40Ar/39Ar dating of oriented amphiboles parallel to the movement direction of the hanging wall on a decollement plane yields a plateau age of 213.1 ± 0.3 Ma and isochron age of 213.4±4.1 Ma, probably representing the age of the later event. The dating of pegmatitic biotites and K-feldspars near the decollement plane from the eastern Fangshan area yield plateau ages of 203.4±0.3 Ma, 203.6±0.4 Ma and 204.8±2.2 Ma, and isochron ages of 204.0±2.0 Ma, 200.6±3.1 Ma and 204.0±5.0 Ma, respectively, implying that the rocks in the studied area had not been cooled down to closing temperature of the dated biotites and K-feldspars until the beginning of the Jurassic (about 204 Ma). The integration of these data with previous chronological ages on the ultrahigh-pressure metamorphism lead to a new inference on the exhumation of the UHPM rocks. The UHPM rocks in the area were exhumed at the rate of 3,4 km/Ma from the mantle (about 80,100 km below the earth's surface at about 240 Ma) to the lower crust (at the depth of about 20-30km at 220 Ma), and at the rate of 1,2 km/Ma to the middle crust (at the depth of about 15 km at 213 Ma), and then at the rate of less than 1 km/Ma to the upper crust about 10 km deep at about 204 Ma. [source]

    Dating of the Karakorum Strike-slip Fault

    ZHOU Yong
    Abstract This paper mainly discusses the timing of the Karakorum strike-slip fault, and gives a brief introduction of its structures, offset, and deformational style. This fault strikes NNW-SSE. Asymmetrical folds, stretching lineation, S-C fabrics, feldspar and quartz s,-porphyroclasts, domino structure, shear cleavages and faults in the fault zone are products of tectonic movements. They all indicate a dextral slip sense of faulting. Mylonitic bands are widely developed along this fault. Phengite appears, indicating rather high deformational pressure. Geochronological data indicate that the Karakorum strike-slip faulting occurred from 6.88±0.36 to 8.75±0.25 Ma. The cumulative displacement from Muztag Ata to Muji is about 135 km. [source]

    Sm-Nd, Pb-Pb and Rb-Sr Isotopic Dating and Its Dynamic Implications for the Proterozoic Augen Granite in the Yunkai Area, Western Guangdong Province

    PENG Songbai
    Abstract The samples of ductile-rheologic deformational augen granite from the Yunkai uplift area, western Guangdong province, were determined by the whole-rock Sm-Nd, Pb-Pb and Rb-Sr isotopic dating to have an Sm-Nd isochron age of 1414±68 Ma, a Pb-Pb isochron age of 1388±90 Ma and a Rb-Sr isochron age of 490±36 Ma. The first two ages are interpreted as the formation age of this suite of granite and the last age represents the timing of the tectono-thermal event of Caledonian ductile-rheologic shear partial melting. It is indicated that in the study area not only an orogeny took place in the Caledonian, but also a more important tectono-magmatic activity occurred in the Meso-proterozoic there, which may be related to the subduction-collision between the Yangtze block and Cathaysia block. [source]

    SHRIMP Zircon U-Pb and Molybdenite Re-Os Datings of the Superlarge Donggou Porphyry Molybdenum Deposit in the East Qinling, China, and Its Geological Implications

    YE Huishou
    Abstract: Located in the eastern part of the East Qinling molybdenum belt, the Donggou deposit is a superlarge porphyry molybdenum deposit discovered in recent years. The authors performed highly precise dating of the mineralized porphyry and ores in the Donggou molybdenum deposit. A SHRIMP U-Pb zircon dating of the Donggou aluminous A-type granite-porphyry gave a rock-forming age of 112±1 Ma, and the ICP-MS Re-Os analyses of molybdenite from the molybdenum deposit yielded Re-Os model ages ranging from 116.5±1.7 to 115.5±1.7 Ma for the deposit. The ages obtained by the two methods are quite close, suggesting that the rocks and ores formed approximately at the same time. The Donggou molybdenum deposit formed at least 20 Ma later than the Jinduicheng, Nannihu, Shangfanggou and Leimengou porphyry molybdenum deposits in the same molybdenum belt, implying that these deposits were formed in different tectonic settings. [source]