Journal articles on the topic 'Maximum age of deposition'
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1
Vermeesch, Pieter. "Maximum depositional age estimation revisited." Geoscience Frontiers 12, no. 2 (March 2021): 843–50. http://dx.doi.org/10.1016/j.gsf.2020.08.008.
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Dunshea, F. R., D. K. Kerton, P. D. Cranwell, R. G. Campbell, B. P. Mullan, R. H. King, and J. R. Pluske. "Dietary lysine requirements of heavy and light pigs weaned at 14 days of age." Australian Journal of Agricultural Research 51, no. 5 (2000): 531. http://dx.doi.org/10.1071/ar99162.
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Seventy 14-day-old male pigs that were either heavy (6.0 kg) or light (3.6 kg) for age were weaned into individual pens and fed 1 of 7 diets containing 9.2–21.0 g lysine/kg feed in a study designed to determine the effect of dietary lysine and weight on lysine requirements of pigs. Five pigs from each weight group were used to determine initial body composition. When pigs reached 10 kg they were slaughtered and empty body composition was analysed to determine protein tissue accretion rates. Protein deposition rate was not affected by weight at weaning but increased with dietary lysine content before reaching a plateau. The relationship between protein deposition (PD, g/day) and dietary lysine (L, g/kg) was described by 3 models. The rectilinear model, which had a linear ascending phase (PD = 4.84 + 1.948L, R2 = 0.935, P = 0.002) and a horizontal component representing maximum protein deposition rate of 32.3 g/day, revealed that maximum protein deposition occurred at 14.1 g lysine/kg. The quadratic function (PD = – 2.74 + 3.74L – 0.099L2 , R2 = 0.916, P = 0.003) provided an estimate of the lysine requirement of 14.9 g lysine/kg occurring at a point where PD reached 95% of the maximum protein deposition rate (32.5 g/day). Use of an asymptotic model (PD = 32.60 – 186 0.727L, R2 = 0.919, P = 0.003) provided an estimate of 14.9 g lysine/kg occurring at a point where PD reached 95% of the maximum protein deposition rate (32.6 g/day). These data indicate that early weaned pigs should be fed a highly digestible diet containing 14–15 g lysine/kg to maximise protein deposition.
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Allaman, Ivan Bezerra, Rafael Vilhena Reis Neto, Rilke Tadeu Fonseca de Freitas, Priscila Vieira Rosa, Aline de Assis Lago, and Adriano Carvalho Costa. "Deposition of bodily chemical components in the carcass of tilapia (Oreochromis sp.) strains." Ciência e Agrotecnologia 38, no. 5 (October 2014): 487–96. http://dx.doi.org/10.1590/s1413-70542014000500008.
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The knowledge of how animals deposited chemical components as water, protein, fat and ash in the carcass is importance for the formulation of a balanced diet, allowing maximum performance with a low environmental impact. So, the study was carried out to evaluate the influence of different tilapia strains (Chitralada, Commercial, Red and Universidade Federal de Lavras [UFLA]) on the deposition of bodily chemical components in the carcass. The bodily components analyzed were water, protein, fat and ash. For the determination of the bodily chemical deposition curves by age, the exponential, Brody, logistic, Gompertz and von Bertalanffy models were adjusted. The Commercial and UFLA strains deposited water at a faster speed (P<0.05) compared with the remaining strains. As for protein, the Red strain had a lower estimated maturity weight (49.37 g), and was more precocious (202 days) with regard to maximum deposition in comparison to the other strains (Chitralada, UFLA and Commercial) in which there was an estimated maturity weight of 231.5 g and maximum depositionfor 337 days. There were no differences (P>0.05) for the logistic model parameter between Red, UFLA and Commercial strains for fat, which presented a maximum fat deposition (0.23 g) at 310 days of age. Regarding ash deposition, the Commercial strain presented a higher maximum deposition (0.10 g) at 337 days, occurring later than the other strains that presented maximum deposition (0.033g) at 254 days of age. Thus, it was concluded that the genetic strains evaluated differ in chemical deposition curves of water, protein, fat and ash.
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Nash, Thomas A., Jessica L. Conroy, David A. Grimley, William R. Guenthner, and Ben Brandon Curry. "Episodic deposition of Illinois Valley Peoria silt in association with Lake Michigan Lobe fluctuations during the last glacial maximum." Quaternary Research 89, no. 3 (September 21, 2017): 739–55. http://dx.doi.org/10.1017/qua.2017.66.
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AbstractThe chronology and cause of millennial depositional oscillations within last glacial loess of the Central Lowlands of the United States are uncertain. Here, we present a new age model that indicates the Peoria Silt along the Illinois River Valley accumulated episodically from ~28,500 to 16,000 cal yr BP, as the Lake Michigan Lobe margin fluctuated within northeastern Illinois. The age model indicates accelerated loess deposition coincident with regional glacial advances during the local last glacial maximum. A weakly developed paleosol, the Jules Geosol, represents a period of significantly slower deposition, from 23,700 to 22,000 cal yr BP. A gastropod assemblage-based reconstruction of mean July temperature shows temperatures 6–10°C cooler than modern during Peoria Silt deposition. Stable oxygen and carbon isotope values (δ18O and δ13C) of gastropod carbonate do not vary significantly across the pedostratigraphic boundary of the Jules Geosol, suggesting slower loess accumulation was a result of reduced glacial sediment supply rather than direct climatic factors. However, a decrease in δ18O values occurred between 26,000 and 24,000 cal yr BP, synchronous with the Lake Michigan Lobe’s southernmost advance. This δ18O decrease suggests a coupling of regional summer hydroclimate and ice lobe position during the late glacial period.
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Natanson, Lisa J., Gregory B. Skomal, Sarah L. Hoffmann, Marianne E. Porter, Kenneth J. Goldman, and David Serra. "Age and growth of sharks: do vertebral band pairs record age?" Marine and Freshwater Research 69, no. 9 (2018): 1440. http://dx.doi.org/10.1071/mf17279.
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Inaccurate age estimates can have severe consequences in the management of elasmobranchs. Numerous studies in shark age validation have demonstrated a disconnect between band pair counts and age, resulting in age underestimation, particularly in older individuals. To investigate the relationship between band pairs, vertebral shape and growth, we quantified intracolumn differences in centrum morphology (size and structure) and band pair counts in seven shark species: Squatina dumeril, Carcharodon carcharias, Lamna nasus, Isurus oxyrinchus, Alopias vulpinus, Prionace glauca and Carcharhinus obscurus. In all species examined, band pair deposition was closely related to body girth and the structural properties of the cartilaginous skeleton, relative to maximum size, and body type. These results have strong implications for accurately assessing age for fisheries management of these species.
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Dorigam, Juliano Cesar De Paula, Nilva Kazue Sakomura, Edney Pereira Da Silva, and João Batista Kochenborger Fernandes. "Modelling the maximum potential of nitrogen deposition and requirements of lysine for broilers." Animal Production Science 54, no. 12 (2014): 1953. http://dx.doi.org/10.1071/an14536.
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This study aimed to develop a dynamic model to estimate lysine (Lys) requirements based on the maximum theoretical potential of nitrogen deposition (NDmaxT) and metabolic bodyweight (MBW) of growing broilers. Three N balance trials were conducted (6–21, 22–37 and 38–53 days of age) at average ages of 14, 30 and 46 days, respectively, with 36 male broilers (Cobb 500) used in each trial. In each trial, the NDmaxT was estimated by exponential model fitting of daily N intake as a function of daily N deposition for the average age. The N deposition was obtained by application of the N balance technique. To model the NDmaxT in relation to MBW, the mean and standard deviation of NDmaxT was used to generate a new population. The critical exponential model was fitted to estimate the daily NDmaxT, resulting in the following model: NDmaxT = 1677 + (–1677 + 13810 × MBW) × (0.151MBW). The daily NDmaxT data so generated were used in the Goettingen model to calculate the daily Lys requirements for N retention response. Modelling of Lys requirements resulted in greater than recommended values, with an average difference of 1.05 times the recommendation of the management guide for the studied strain. According to the results obtained from this simulation, the model provided consistent estimates of Lys requirements and may enable nutritionists to provide nutritional strategies to optimise production of broilers based on the MBW.
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Owen, Richard, Christopher Richardson, and Hilary Kennedy. "The influence of shell growth rate on striae deposition in the scallop Pecten maximus." Journal of the Marine Biological Association of the United Kingdom 82, no. 4 (August 2002): 621–23. http://dx.doi.org/10.1017/s0025315402005969.
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The relationship between shell growth rate and striae deposition was investigated in a field study in which groups of juvenile scallops, Pecten maximus, (Pectinidae: Bivalvia) were deployed for monthly periods over a year in the Menai Strait (North Wales). The number of striae deposited per day, inter-striae width (the increment of shell deposited between successive striae) and striae abundance (the number of striae deposited per mm of shell height) all correlated well with measured shell growth rates. During the winter months, when seawater temperatures were minimal (6°C), inter-striae width declined, whilst striae abundance increased, whereas during the summer when seawater temperatures were maximal (18°C), shell growth was rapid with maximum inter-striae width, resulting in a seasonal pattern of narrowly grouped, then widely spaced striae. This seasonal pattern in inter-striae width variation provides an accurate and reliable method for estimating the number of growth cycles and hence the age of P. maximus.
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Orme, Devon A., and Kathleen D. Surpless. "The birth of a forearc: The basal Great Valley Group, California, USA." Geology 47, no. 8 (June 6, 2019): 757–61. http://dx.doi.org/10.1130/g46283.1.
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AbstractThe Great Valley basin of California (USA) is an archetypal forearc basin, yet the timing, structural style, and location of basin development remain controversial. Eighteen of 20 detrital zircon samples (3711 new U-Pb ages) from basal strata of the Great Valley forearc basin contain Cretaceous grains, with nine samples yielding statistically robust Cretaceous maximum depositional ages (MDAs), two with MDAs that overlap the Jurassic-Cretaceous boundary, suggesting earliest Cretaceous deposition, and nine with Jurassic MDAs consistent with latest Jurassic deposition. In addition, the pre-Mesozoic age populations of our samples are consistent with central North America sources and do not require a southern provenance. We interpret that diachronous initiation of sedimentation reflects the growth of isolated depocenters, consistent with an extensional model for the early stages of forearc basin development.
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MEINHOLD, GUIDO, and DIRK FREI. "Detrital zircon ages from the islands of Inousses and Psara, Aegean Sea, Greece: constraints on depositional age and provenance." Geological Magazine 145, no. 6 (September 16, 2008): 886–91. http://dx.doi.org/10.1017/s0016756808005505.
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AbstractU–Pb LA–SF–ICP–MS analyses of detrital zircons from a metalitharenite on Inousses Island, Greece, gave major age groups of 310–350, 450–500, 550–700, 900–1050 and 1880–2040 Ma and minor peaks between 2600 and 2800 Ma. The youngest concordant zircon grains of 310–330 Ma indicate the maximum age of deposition to be Late Carboniferous, rather than Ordovician, as had been earlier assumed. The lack of zircon ages between 1.1 and 1.8 Ga, coupled with the occurrence ofc.2-Ga-old zircons, imply a northern Gondwana-derived source. Detrital zircons from a garnet–mica schist on Psara Island yielded a major age group ofc.295–325 Ma and only minor Early Palaeozoic and Late Neoproterozoic ages. The youngest grains around 270 Ma indicate the maximum age of deposition to be Late Permian. The Early Palaeozoic ages support a source from terranes at the southern margin of Laurussia during the Late Palaeozoic and hence clarify the palaeotectonic position of units from the eastern Aegean Sea within the Palaeotethyan realm.
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HORÁK, JANA M., and JANE A. EVANS. "Early Neoproterozoic limestones from the Gwna Group, Anglesey." Geological Magazine 148, no. 1 (June 16, 2010): 78–88. http://dx.doi.org/10.1017/s0016756810000464.
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AbstractLimestone megaclasts up to hundreds of metres in size are present within the Gwna Group mélange, North Wales, UK. The mélange has been interpreted as part of a Peri-Gondwanan fore-arc accretionary complex although the age of deposition remains contentious, proposals ranging from Neoproterozoic to Early Ordovician. This paper uses strontium isotope chemostratigraphy to establish the age of the limestone blocks and thus provide a maximum age constraint on mélange formation. Results show that, although the carbonates are locally dolomitized, primary87Sr/86Sr ratios can be identified and indicate deposition sometime between the late Tonian and earliest Cryogenian. This age is older than that suggested by stromatolites within the limestone and indicates that the limestone did not form as cap carbonate deposits.
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Watts, Peter, and David E. Gaskin. "A comparison of age determination techniques for the harbour porpoise, Phocoena phocoena L." Canadian Journal of Zoology 67, no. 7 (July 1, 1989): 1832–36. http://dx.doi.org/10.1139/z89-261.
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The maximum life-span of the harbour porpoise has been estimated at 13 years (based upon dentinal growth layer groups in the teeth) and at 21 years (based upon growth layers in the periosteal bone of the mandible). We used both techniques to estimate the ages of 120 harbour porpoises from the western North Atlantic, in an attempt to determine the relative reliability of each technique. Dentinal layering was the better predictor of body length. Mandibular layering was highly variable even within a single cross section in most specimens, as a result of both common bifurcation of the layers and destruction of the inner layers by growth and remodelling of the living bone. Furthermore, mandibular layers appear to be deposited at a rate of 2 layers/year, double the deposition rate of dentinal growth layer groups. Age estimates which assume annual deposition of mandibular layers therefore overestimate true age.
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Goodfriend, Glenn A. "Chronostratigraphic Studies of Sediments in the Negev Desert, Using Amino Acid Epimerization Analysis of Land Snail Shells." Quaternary Research 28, no. 3 (November 1987): 374–92. http://dx.doi.org/10.1016/0033-5894(87)90005-6.
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AbstractThe chronostratigraphy of mostly Holocene sediments in the Northern Negev desert of Israel was studied through amino acid epimerization analysis (alloisoleucine/isoleucine ratio, A/I) of individual land snail shells and 14C analysis of bulk samples of land snail shells contained within the sediments. Analysis of 31 deposits shows a very strong correlation between A/I and 14C age. A/I analyses indicate that age mixtures occur within all colluvial and in some fluvial deposits. Consequently, radiocarbon dates of bulk samples, which give an average age, overestimate the time of deposition. Sedimentation rates were generally rapid in both fluvial and colluvial deposits. Colluviation shows a maximum in the early Holocene and decreases progressively thereafter, in accordance with the change in average rainfall. Accumulation of fluvial sediments shows a distinct mid-Holocene maximum and apparently relates to the interaction between variation in rainfall, extent of bedrock exposure, and vegetation density. Late Holocene fluvial deposition may relate to agricultural activity. The understanding of the chronology of sedimentation is dependent on an integrated approach employing amino acid epimerization analysis to study age variation within a layer and 14C analyses for establishment of an absolute chronology.
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Hesse, Paul P., Geoff S. Humphreys, Barton L. Smith, James Campbell, and Elizabeth K. Peterson. "Age of loess deposits in the Central Tablelands of New South Wales." Soil Research 41, no. 6 (2003): 1115. http://dx.doi.org/10.1071/sr02152.
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Basal optically stimulated luminescence (OSL) ages of more than 50 000 years in loessic (parna) mantles on the Central Tablelands of New South Wales indicate significant aeolian silt (c. 30 μm mode) deposition commenced well before the onset of the last glacial maximum. Each mantle consists of >1 m of reddish silty clay loam–silty clay with an earthy fabric which sits atop manganese and iron pans and saprolite. Mixing of saprolite-derived material into the pans and also into the silty layer indicates a site history of steady accumulation of aeolian loess and continual pedogenesis. No palaeosols are found. The OSL chronology of both sites, while low resolution, indicates an almost constant mass accumulation rate from 50 000 years ago through the last glacial maximum and into the Holocene. Local factors affecting retention of deposited dust may be responsible for the apparent passivity of the sites.
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Sherwood, John E., Jim M. Bowler, Stephen P. Carey, John Hellstrom, Ian J. McNiven, Colin V. Murray-Wallace, John R. Prescott, et al. "The Moyjil site, south-west Victoria, Australia: chronology." Proceedings of the Royal Society of Victoria 130, no. 2 (2018): 32. http://dx.doi.org/10.1071/rs18005.
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An unusual shell deposit at Moyjil (Point Ritchie), Warrnambool, in western Victoria, has previously been dated at 67±10 ka and has features suggesting a human origin. If human, the site would be one of Australia’s oldest, justifying a redetermination of age using amino acid racemisation (AAR) dating of Lunella undulata (syn. Turbo undulatus) opercula (the dominant shellfish present) and optically stimulated luminescence (OSL) of the host calcarenite. AAR dating of the shell bed and four Last Interglacial (LIG) beach deposits at Moyjil and Goose Lagoon, 30 km to the west, confirmed a LIG age. OSL analysis of the host sand revealed a complex mixing history, with a significant fraction (47%) of grains giving an early LIG age (120–125 ka) using a three-component mixing model. Shell deposition following the LIG sea-level maximum at 120–125 ka is consistent with stratigraphic evidence. A sand layer immediately below the shell deposit gave an age of ~240 ka (i.e. MIS 7) and appears to have been a source of older sand incorporated into the shell deposit. Younger ages (~60–80 ka) are due to bioturbation before calcrete finally sealed the deposit. Uranium/thorium methods were not applicable to L. undulata opercula or an otolith of the fish Argyrosomus hololepidotus because they failed to act as closed systems. A U–Th age of 103 ka for a calcrete sheet within the 240 ka sand indicates a later period of carbonate deposition. Calcium carbonate dripstone from a LIG wave-cut notch gave a U–Th age of 11–14 ka suggesting sediment cover created a cave-like environment at the notch at this time. The three dating techniques have collectively built a chronology spanning the periods before and after deposition of the shell bed, which occurred just after the LIG sea-level maximum (120–125 ka).
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Ricketts, B. D. "Possible plinian eruptions of Paleocene age in central Yukon: evidence from volcanic ash, Norman Wells area, N.W.T." Canadian Journal of Earth Sciences 22, no. 3 (March 1, 1985): 473–79. http://dx.doi.org/10.1139/e85-046.
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Composite tuff units up to 17 m thick are exposed in strata of the Summit Creek Formation, south of Fort Norman, Northwest Territories. The age of the tuffs is bracketed between late Maastrichtian and Early Paleocene based on palynology. The geometry of the tuff beds, their consistently fine grain size (maximum particle size is 0.25 mm), their composition (less than 5% dense juvenile ash particles), and burial of plants in growth position suggest deposition by fallout from a high-altitude column of ash. Between 100 and 300 eruption–deposition events are preserved in the sequence.The nearest known volcanic source vents are located in central Yukon, about 600 km from the present exposures. Estimates of dispersal area and of volume of single ash layers and the degree of particle fragmentation compare favourably with similar parameters that have been determined from geologically recent plinian and ultraplinian eruptions.
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Peng, Peng, Fu Liu, MingGuo Zhai, and JingHui Guo. "Age of the Miyun dyke swarm: Constraints on the maximum depositional age of the Changcheng System." Chinese Science Bulletin 57, no. 1 (October 17, 2011): 105–10. http://dx.doi.org/10.1007/s11434-011-4771-x.
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Corfu, F., and G. M. Stott. "U–Pb ages for late magmatism and regional deformation in the Shebandowan Belt, Superior Province, Canada." Canadian Journal of Earth Sciences 23, no. 8 (August 1, 1986): 1075–82. http://dx.doi.org/10.1139/e86-108.
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Five precise U–Pb zircon (and titanite) ages from different lithologic units of the Shebandowan greenstone belt in the western Wawa Subprovince of the Superior Province put tight constraints on the time of late Archean magmatism and of two major deformation events.A porphyry sill from the older supracrustal sequence has an age of 2733 ± 3 Ma. Another porphyritic rock, a trondhjemite occurring as a clast in a conglomerate of the unconformably overlying Timiskaming-type supracrustal sequence, formed 2704 ± 2 Ma ago and defines a maximum age for the deposition of the Timiskaming-type sequence. An alkalic volcanic rock from this sequence has been directly dated at [Formula: see text], in accord with the above constraint and with another probable maximum age of deposition given by the date of 2696 ± 2 Ma for the Shebandowan Lake Pluton. A first deformation event (D1) was related to a predominantly vertical tectonic regime and occurred during or before intrusion of the Shebandowan Lake Pluton at 2696 ± 2 Ma. The second deformation event (D2) was caused by northwesterly-directed compression and occurred after [Formula: see text] ago, the age of the Timiskaming-type volcanic rocks. A minimum age for the D2 deformation event, which also affected the adjacent Quetico metasedimentary belt and was probably related to the development of major transcurrent fault systems throughout the Superior Province, is provided by an age of [Formula: see text] for the undeformed, late-kinematic Burchell Lake Pluton.
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Gusev, Nikolay I., Lyudmila Yu Sergeeva, and Sergey G. Skublov. "Dating the Sedimentary Protolith of the Daldyn Group Quartzite, Anabar Shield, Russia: New Detrital Zircon Constraints." Geosciences 10, no. 6 (May 30, 2020): 208. http://dx.doi.org/10.3390/geosciences10060208.
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Quartzites and paragneisses of the Archean granulite series of the Anabar Shield (Siberian Craton, Russia) are described geochemically. The Sm-Nd isotope systematics of the rocks and the U-Pb age (SHRIMP II) and geochemistry of zircons from quartzites and paragneisses are studied. Newly formed zircons from quartzites display geochemical characteristics of the magmatic type and were produced by rock anatexis upon granulite-facies metamorphism. The Paleoproterozoic age of the latest detrital zircons, 2250 ± 24 Ma, constrains the maximum age of sedimentary rock deposition. The anatectic rims around detrital zircons were formed ca. 2000 ± 9 Ma ago. The time of deposition of the sedimentary protolith of gneisses and quartzites falls within the age interval of the above-mentioned dates and is tentatively accepted as 2.1 Ga. The presence of Paleoproterozoic metasedimentary rocks in the Daldyn Group implies the tectonic heterogeneity of the series and the existence of Paleoproterozoic rock bodies among the predominant Archean rock sequences.
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Thomas, David S. G., Mark D. Bateman, Daryoush Mehrshahi, and Sarah L. O'Hara. "Development and Environmental Significance of an Eolian Sand Ramp of Last-Glacial Age, Central Iran." Quaternary Research 48, no. 2 (September 1997): 155–61. http://dx.doi.org/10.1006/qres.1997.1923.
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AbstractA 25-m-thick section of mostly eolian sediment is exposed in the stream-cut flank of a sand ramp accumulated in a mountain saddle near Ardakan playa, central Iran. The well-sorted eolian sediments of the ramp contain talus beds and incipient paleosols. Morphology and bedding structures imply that southeasterly winds were primarily responsible for deposition of the eolian sand. Optical dating shows that the sand was deposited near the last glacial maximum within about 5000 yr. Surface stabilization, lack of surface scree, and the development of a stream cut between the mountain and the ramp show that sediment accumulation ceased after this time. The Siberian high pressure system may have been established over central Iran during the last glacial maximum, causing cooler temperatures and a prevalence of southeasterly winds. These colder, windier conditions would have led to frost shattering and eolian transport, both of which are not significant processes today but which are evident as past processes from the ramp sediments.
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Hoving, Hendrik Jan T., and Marek R. Lipiński. "Female reproductive biology, and age of deep-sea squid Histioteuthis miranda from southern Africa." ICES Journal of Marine Science 66, no. 9 (June 9, 2009): 1868–72. http://dx.doi.org/10.1093/icesjms/fsp163.
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Abstract Hoving, H. J. T., and Lipiński, M. R. 2009. Female reproductive biology, and age of deep-sea squid Histioteuthis miranda from southern Africa. – ICES Journal of Marine Science, 66: 1868–1872. Data on female reproductive strategy and male and female length–weight relationships and age are presented for the mesopelagic squid Histioteuthis miranda. Females exhibit synchronous ovulation, indicating that eggs are spawned at once or over a short period. The maximum potential fecundity seems to range from 89 000 to 148 000 oocytes. Assuming daily deposition of statolith increments, maturing females were 10–15 months old. Male H. miranda mature young (∼6 months) and reach at least 15 months old.
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Osokpor, Jerry, and Efetobore G. Maju-Oyovwikowhe. "Paleodepositional Environment and Sequence Stratigraphy of Miocene Sediments in Well TN-1, Coastal Swamp Depobelt, Niger Delta Basin, Nigeria." Tanzania Journal of Science 47, no. 5 (December 1, 2021): 1530–45. http://dx.doi.org/10.4314/tjs.v47i5.4.
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This research focused on the interpretation of paleodepositional environment and development of a sequence stratigraphic framework for the well TN-1 section, located in the coastal swamp depositional belt of the Niger Delta Basin. Integration of interpreted litho- and biofacies data sets that facilitated the interpretation of the paleodepositional environment enabled the erection of a sequence-stratigraphic framework. Three lithotypes (sand, clay, and shale) distributed within fourteen facies variants were integrated with palynomorph components to delineate five paleodepositional cycles ranging from distal delta plain to bathyal. Eight systems tracts (closely related to depositional cycles, but transcended depositional boundaries in some intervals) that hosted three maximum flooding surfaces (MFS), three sequence boundaries (SBs), distributed within four third-order and three second-order sequences, were defined. Age-significant palynomorphs recovered indicated an Aquitanian to Messinian age range (with non-deposition or erosion of Burdigalian, Langhian, Serravallian Stages sediments), distributed within five pollen zones (P628–P840) that correlated with published global cycles. This study demonstrates the significance of integrated studies to erect a sequence-stratigraphic framework applicable for field and basin-scale exploration and exploitation purposes.
Keywords: Sequence stratigraphy, paleodepositional cycles, systems tract, cyclic sedimentation,lithofacies analysis, integrated studies.
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Alexeev, N. L., V. A. Maslov, V. D. Kaminsky, V. S. Semenov, E. S. Bogomolov, I. N. Kapitonov, N. A. Gonzhurov, A. Yu Melnik, and M. S. Yegorov. "New data on the age of metamorphic rocks from the granite-greenstone ruker terrane (the southern Prince Charles Mountains, East Antarctica)." Доклады Академии наук 487, no. 6 (September 10, 2019): 644–49. http://dx.doi.org/10.31857/s0869-56524876644-649.
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Paper presents results of isotope studies of primary igneous and sedimentary rocks of Mawson and Menzies series from the southern Prince Charles Mountains, East Antarctica. Obtained data show that igneous protholith crystallization of Mawson orthogneiss occurred at 3164,2±9,2-3163,2±7,8 Ma ago. The Mawson orthogneiss were a basement for Menzies series sediment. The maximum time of sediment deposition is estimated to be in the range of 3,0-3,1 Ga. Sediment protholith involves an admixture of Paleoarchean material.
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Schiøtte, L., W. Compston, and D. Bridgwater. "U–Th–Pb ages of single zircons in Archaean supracrustals from Nain Province, Labrador, Canada." Canadian Journal of Earth Sciences 26, no. 12 (December 1, 1989): 2636–44. http://dx.doi.org/10.1139/e89-224.
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Ion-probe U–Pb dating of igneous zircons from an acid metavolcanite belonging to the Nulliak supracrustal association of the Saglek area, northern Labrador, suggests an original age of 3776 ± 8 Ma (2σ), interpreted as the deposition age of the volcanite. In accordance with the field model, this is slightly but significantly older than the previously obtained ion-probe U–Pb age of igneous zircons from the main phase of the Uivak gneisses, which carries inclusions of the supracrustal association. A secondary event of zircon growth recorded in the metavolcanite has a maximum age of 3065 ± 8 Ma (2σ).A metapelite belonging to the Weekes amphibolite supracrustal association of the Hopedale area south of Nain contains rounded, low-U zircons of 3258 ± 24 Ma (2σ) age. Occasional textural evidence suggests that some of these zircons are most likely detrital grains of igneous origin, in which case 3258 ± 24 Ma is a minimum age of the source from which the sediment was derived and a maximum age for the deposition of the sediment. However, the possibility that the age represents recrystallization of the sediment under high-grade conditions cannot be ruled out. A 2841 ± 5 Ma (2σ) age obtained on a younger generation of euhedrally zoned high-U zircons from the metapelite is within error of the published bulk zircon U–Pb age of the tonalitic component of the Kanairiktok plutonic suite that intrudes the older orthogneiss and supracrustal units in the area. These younger zircons are most likely to have grown during migmatization of the metasediment at the time of emplacement of the suite.The zircon data give no positive evidence to support correlation between the Nulliak supracrustals and the Weekes amphibolite association.
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Marchetti, David W., M. Scott Harris, Christopher M. Bailey, Thure E. Cerling, and Sarah Bergman. "Timing of glaciation and last glacial maximum paleoclimate estimates from the Fish Lake Plateau, Utah." Quaternary Research 75, no. 1 (January 2011): 183–95. http://dx.doi.org/10.1016/j.yqres.2010.09.009.
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AbstractThe High Plateaus of Utah include seven separate mountain ranges that supported glaciers during the Pleistocene. The Fish Lake Plateau, located on the eastern edge of the High Plateaus, preserves evidence of at least two glacial advances. Four cosmogenic 3He exposure ages of boulders in an older moraine range from 79 to 159 ka with a mean age of 129 ± 39 ka and oldest ages of 152 ± 3 and 159 ± 5 ka. These ages suggest deposition during the type Bull Lake glaciation and Marine Oxygen Isotope Stage (MIS) 6. Twenty boulder exposure ages from four different younger moraines indicate a local last glacial maximum (LGM) of ~ 21.1 ka, coincident with the type Pinedale glaciation and MIS 2. Reconstructed Pinedale-age glaciers from the Fish Lake Plateau have equilibrium-line altitudes ranging from 2950 to 3190 m. LGM summer temperature depressions for the Fish Lake Plateau range from −10.7 to −8.2°C, assuming no change in precipitation. Comparison of the Fish Lake summer temperature depressions to a regional dataset suggests that the Fish Lake Plateau may have had a slight increase (~ 1.5× modern) in precipitation during the LGM. A series of submerged ridges in Fish Lake were identified during a bathymetric survey and are likely Bull Lake age moraines.
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Auldist, D. E., F. L. Stevenson, M. G. Kerr, P. Eason, and R. H. King. "Lysine requirements of pigs from 2 to 7 kg live weight." Animal Science 65, no. 3 (December 1997): 501–7. http://dx.doi.org/10.1017/s1357729800008705.
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AbstractThirty-two male pigs were used to investigate the effects of nine levels of dietary lysine ranging from 0·41 to 1·30 g lysine per MJ gross energy (GE) on the performance of pigs weaned at 1 to 2 days of age and growing between 2 and 7 kg live weight. The nine dietary lysine treatments, which contained similar levels of GE and balance of essential amino acids, were offered to the pigs at a common feeding level of 2·0 MJ GE per kg metabolic live weight (M075) per day. Growth performance and protein deposition rates increased linearly with increasing dietary lysine content up to about 0·97 g lysine per MJ GE and remained relatively constant thereafter. The response of protein deposition (PD, g/day) in the whole body of pigs to dietary lysine (L, g lysine per MJ GE) was described by three models. The respective regression equation for the quadratic function was PD = -14·23 + 87·66 L – 36·00 L2 and maximum protein deposition occurred at 1·22 g lysine per MJ GE. The rectilinear model, which had an ascending linear phase (PD = 1·49 + 40·10 L, R2 = 0·98, P < 0·001) and a horizontal component representing a mean protein deposition rate of 39·7g/day revealed that maximum protein deposition occurred at 0·95g lysine per MJ GE. Finally, application of the asymptotic model also revealed a highly significant equation: PD = 43·40 — 79·99 × 0·07111, R2 = 0·94, P < 0·001; which indicates a dietary requirement of 1·07 g lysine per MJ GE assuming that the dietary requirement was estimated at 0·90 of the asymptote maximal value. The results indicate that the dietary lysine requirement for pigs during the first 3 weeks of life appears to have changed little over the past 20 years despite substantial changes in genotype.
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Haugaard, Rasmus, Luke Ootes, Larry M. Heaman, Michael A. Hamilton, Barry J. Shaulis, and Kurt Konhauser. "Depositional timing of Neoarchean turbidites of the Slave craton—recommended nomenclature and type localities." Canadian Journal of Earth Sciences 54, no. 1 (January 2017): 15–32. http://dx.doi.org/10.1139/cjes-2016-0098.
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Two temporally distinct Neoarchean turbidite packages are known to occur in the Slave craton. The older is a greywacke–mudstone succession that includes the renowned Burwash Formation (ca. 2661 Ma). In this study, a previously undated tuff bed is demonstrated to have crystallized at ca. 2650.5 ± 1.0 Ma refining the deposition age of these turbidites between ca. 2661 and 2650 Ma. The younger turbidites are locally distinctive as they contain interstratified banded iron formation (BIF). Previous work demonstrated that the younger turbidites were deposited between ca. 2640 and 2615 Ma, based entirely on maximum depositional ages from detrital zircons. A ∼3 cm thick felsic to intermediate tuff bed was discovered interbedded with these BIF-bearing turbidites. The tuff bed contains a single age population of zircon with a crystallization age of 2620 ± 6 Ma defining the depositional timing of these BIF-bearing turbidites. New U–Pb detrital zircon dates from extensive turbidite sequences in the eastern and central part of the Slave craton are also presented. We use the new and previously published results to recommend nomenclature for these extensive sedimentary rocks in the Slave craton. The ca. 2661–2650 Ma turbidites remain part of the previously ascribed Duncan Lake Group. The younger ca. 2620 Ma turbidites are assigned to the new Slemon Group. Where robust age-data exist, we recommend formation names and include type localities for each.
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Percival, John A., William J. Davis, and Michael A. Hamilton. "U–Pb zircon geochronology and depositional history of the Montresor group, Rae Province, Nunavut, Canada." Canadian Journal of Earth Sciences 54, no. 5 (May 2017): 512–28. http://dx.doi.org/10.1139/cjes-2016-0170.
Full textAbstract:
Paleoproterozoic metasedimentary successions of the northwestern Canadian Shield provide records of tectonic events, but the definition of depositional ages has proved elusive. Although previously poorly understood, the Montresor belt of western Nunavut yields new insight into the 2.2–1.8 Ga time window. On the basis of U–Pb analyses of detrital zircon in sedimentary rocks and igneous zircon in sills, we conclude that arenite of the lower Montresor group was deposited between 2.194 and 2.045 Ga, and arkose of the upper Montresor group after 1.924 Ga, adding constraints on the Rae cover sequence. The lower Montresor arenite yielded an older group (3.05–2.58 Ga) and a younger, more tightly constrained group (2.194 ± 0.014 Ga). Four of six zircon grains analyzed from a gabbro sill within the lower Montresor have discordant 207Pb/206Pb ages (2.71, 2.66, 2.53, and 2.39 Ga) and are considered to be inherited, whereas two grains provide an age of 2045 ± 13 Ma, interpreted to date crystallization and providing a minimum age for the lower Montresor package. Upper Montresor arkose contains detrital zircon with probability density peaks at 2.55–2.25 and 2.1–1.92 Ga, together with scattered older grains (3.8–2.65 Ga). The youngest grain yields an age of 1924 ± 6 Ma, establishing a maximum age for sandstone deposition. Provenance is inferred to have been from the west, where igneous sources of 2.5–2.3 Ga (Queen Maud block) and 2.03–1.89 Ga (Thelon orogen) are known. Collectively, the new ages suggest a minimum 120 million year gap between deposition of the pre-2045 ± 13 Ma lower and post-1924 ± 6 Ma upper parts of the Montresor group. Similar age constraints may apply to other parts of the Rae cover sequence.
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Esteban, José Julián, Julia Cuevas, and José María Tubía. "Peri-Gondwanan Provenance and Geodynamic Evolution of The Guadaiza Nappe (Alpujarride Complex, Betic Cordilleras, Spain): Insights on The Paleotethyan Paleogeography." Minerals 12, no. 3 (March 5, 2022): 325. http://dx.doi.org/10.3390/min12030325.
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Based on the LA-ICP-MS U-Pb zircon ages of four metamorphic samples, we discuss the geochronology and provenance of the Guadaiza nappe, an allochthonous unit that underlies the Ronda peridotites (Betic Cordilleras, Spain). The Guadaiza nappe is composed of Triassic marbles overlying a metapelitic sequence with schists and migmatites. Zircons from a quartzite interlayered with the marbles yield a maximum depositional age of ca. 289 Ma that supports the Triassic age. The idiomorphic morphology of these Paleozoic zircon crystals and the lack of late-Variscan metamorphism (ca. 300 Ma) supports a proximal source area, and suggests that the marbles were discordantly deposited over the metapelitic sequence, along the northern margin of the Alboran microplate. The zircon patterns from the metapelitic sequence mainly yield Paleoproterozoic (ca. 1.6–2.5 Ga), Tonian–Stenian (ca. 1000 Ma), Ediacaran–Cryogenian (ca. 600 Ma) and Paleozoic (ca. 500 Ma) age clusters. These results suggest provenance from areas within the triangle bound by the West African Craton, the Metasaharan Craton and the Hun Superterrane during the Paleotethys opening (Silurian–Devonian). A Silurian–Carboniferous deposition age for the schist protoliths is constrained by the youngest detrital zircon population (ca. 443 Ma) and the Variscan age of their migmatization by an additional peak of around 299 Ma in the migmatites.
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Schulz, Holger, Gunter Eder, Ines Bolle, Akira Tsuda, and Stefan Karrasch. "Micron-sized intrapulmonary particle deposition in the developing rat lung." Journal of Applied Physiology 112, no. 5 (March 1, 2012): 759–65. http://dx.doi.org/10.1152/japplphysiol.01064.2011.
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Little is known about the effects of postnatal developmental changes in lung architecture and breathing patterns on intrapulmonary particle deposition. We measured deposition in the developing Wistar-Kyoto rat, whose lung development largely parallels that of humans. Deposition of 2-μm sebacate particles was determined in anesthetized, intubated, spontaneously breathing rats on postnatal days (P) 7 to 90 by aerosol photometry (Karrasch S, Eder G, Bolle I, Tsuda A, Schulz H. J Appl Physiol 107: 1293–1299, 2009). Respiratory parameters were determined by body plethysmography. Tidal volume increased substantially from P7 (0.19 ml) to P90 (2.1 ml) while respiratory rate declined from 182 to 107/min. Breath-specific deposition was lowest (9%) at P7 and P90 and markedly higher at P35 (almost 16%). Structural changes of the alveolar region include a ninefold increase in surface area (Bolle I, Eder G, Takenaka S, Ganguly K, Karrasch S, Zeller C, Neuner M, Kreyling WG, Tsuda A, Schulz H. J Appl Physiol 104: 1167–1176, 2008). Particle deposition per unit of time and surface area peaked at P35 and showed a minimum at P90. At an inhaled particle number concentration of 105/cm3, there was an estimated 450, 690, and 330 particles/(min × cm2) at P7, P35, and P90, respectively. Multiple regression models showed that deposition depends on the mean linear intercept as structural component and the breathing parameters, tidal volume, and respiratory rate ( r2 > 0.9). In conclusion, micron-sized particle deposition was dependent on the stage of postnatal lung development. A maximum was observed during late alveolarization (P35), which corresponds to human lungs of about eight years of age. Children at this age may therefore be more susceptible to micron-sized airborne environmental health hazards.
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La Mesa, Mario, and Joseph T. Eastman. "First data on age and sexual maturity of the Tristan klipfish, Bovichtus diacanthus (Bovichtidae) from Tristan da Cunha, South Atlantic." Antarctic Science 24, no. 2 (October 17, 2011): 115–20. http://dx.doi.org/10.1017/s0954102011000733.
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AbstractThe Tristan klipfish, Bovichtus diacanthus, an endemic species at Tristan da Cunha Island was successfully aged using whole sagittal otoliths. The annulation pattern was clear, resulting in an alternating combination of opaque and translucent zones that form an annulus. Although sampling limitations did not allow direct validation of annual ring deposition, most otoliths showed a translucent edge, perhaps suggesting that the deposition of translucent zones is a synchronous process which takes place in winter coincident with the spawning season. The reliability of ageing methodology was supported by the good agreement between readings. The maximum age was estimated to be five years in females and four years in males. In order to increase the small number of direct readings, the length at age was back-calculated for each fish by fitting growth curves. The resulting growth of B.diacanthus was described by the von Bertalanffy growth model, as summarized by the following parameters: L∞ = 207.1 mm TL, k = 0.49 per year, and t0 = 0.04 years. The size at which 50% of the population spawns for the first time was c. 147 mm, corresponding to 2.5 years of age.
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Russell, Anthony P., G. Lawrence Powell, and Dean R. Hall. "Growth and age of Alberta long-toed salamanders (Ambystoma macrodactylum krausei): a comparison of two methods of estimation." Canadian Journal of Zoology 74, no. 3 (March 1, 1996): 397–412. http://dx.doi.org/10.1139/z96-047.
Full textAbstract:
Both skeletochronology and a somatic growth model based upon mark–recapture data were used to estimate life-span and the relationship between size and age in two populations of long-toed salamanders (Ambystoma macrodactylum krausei) in the upper Bow Valley of southwestern Alberta. Skeletochronologically aged salamanders (n = 170) displayed a sigmoidal relationship between snout–vent length and age, with a great deal of variation in snout–vent length within each year class. The modified logistic-by-mass somatic growth model (based upon 47 recaptures) predicted sexual maturity at 3 years of age and adult size at 6 years, with asymptotic length approached at 15 years of age. These predictions were falsified by skeletochronology, which indicated that a snout–vent length characteristic of sexual maturity could be reached by 2 years and adult size by 3 years of age, and that the maximum life-span attained was 10 years, with most individuals living 6 years at most. Considerable variation in growth, evidently due to factors other than simple age, is displayed among individuals in these populations. Their demographic characteristics suggest that the skeletochronologically determined maximum age is real and not due to a cessation of growth, and thus of bone deposition, in these salamanders.
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Caltabellotta, F. P., F. M. Silva, F. S. Motta, and O. B. F. Gadig. "Age and growth of the threatened endemic skate Rioraja agassizii (Chondrichthyes, Arhynchobatidae) in the western South Atlantic." Marine and Freshwater Research 70, no. 1 (2019): 84. http://dx.doi.org/10.1071/mf18010.
Full textAbstract:
The Rio skate Rioraja agassizii is a threatened endemic skate species frequently caught as bycatch in the western South Atlantic. However, there is no biological information about its age and growth parameters, which would be necessary to provide science-based information for the development of management strategies for this species. The aim of the present study was to provide information about the age and growth parameters of R. agassizii. In all, 138 vertebrae from individuals ranging in size from 9.0 to 53.2-cm total length (TL) were analysed. The edge analysis indicated a trend for annual band deposition in the vertebrae. Maximum ages estimated for males and females were 6 and 10 years respectively. Akaike’s information criterion indicated that the modified two-parameter form of the von Bertalanffy growth function (using length at birth L0=9.0cm TL) provided the best fit, with derived parameters of theoretical maximum length L∞=49.6cm TL and growth coefficient k=0.27 for males and L∞=59.0cm TL and k=0.22 for females. Our results are important to understanding the resilience of this skate species to harvest, which can contribute to the development of fisheries management strategies and conservation programs.
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Whalen, J. B., A. Zagorevski, V. J. McNicoll, and N. Rogers. "Geochemistry, U–Pb geochronology, and genesis of granitoid clasts in transported volcanogenic massive sulfide ore deposits, Buchans, Newfoundland." Canadian Journal of Earth Sciences 50, no. 11 (November 2013): 1116–33. http://dx.doi.org/10.1139/cjes-2013-0040.
Full textAbstract:
The Buchans Group, central Newfoundland, represents an Ordovician continental bimodal calc-alkaline arc sequence that hosts numerous volcanogenic massive sulfide (VMS) occurrences, including both in situ and mechanically transported sulfide breccia–conglomerate orebodies. Diverse lithic clasts associated with transported deposits include rounded granitoid clasts. Earlier workers have suggested that Buchans Group VMS-hosting felsic extrusive units, small granodiorite intrusions (e.g., Wiley’s Brook), and granitoid cobbles associated with transported ore represent co-genetic products of the same magmatic system. The granitoid cobbles and small granodiorite intrusions are geochemically similar and closely resemble Buchans Group felsic volcanic units. U–Pb zircon age determinations show a (i) 466.7 ± 0.5 Ma crystallization age for the Wiley’s Brook granodiorite (WBG), (ii) 464 ± 4 Ma crystallization age for a granitoid cobble, and (iii) 466 ± 4 Ma maximum deposition age for a conglomerate–sandstone sequence associated with transported ore. Thus, Buchans Group felsic plutonic rocks are within experimental error of felsic volcanism and VMS deposition. Furthermore, εNd (T) (T, time of crystallization) values of four granitoid cobbles (–1.95 to –4.0) overlap values obtained from Buchans Group felsic volcanic units. Our results are compatible with plutonic and volcanic rocks being related through fractional crystallization or partial melting processes but do not support a petrogenetic link between VMS deposition and exposed felsic plutons. Comparisons to modern arc analogues favour exhumation of plutonic rocks by extension along caldera or rift walls and (or) subaerial erosion. Enigmatic rounding of Buchans granitoid clasts was likely accomplished in a subaerial or shallow marine environment, and the clasts transported into a VMS-active basin by mass flows.
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Man, Ruiqi, Zhijun Wu, Taomou Zong, Aristeidis Voliotis, Yanting Qiu, Johannes Größ, Dominik van Pinxteren, et al. "Impact of water uptake and mixing state on submicron particle deposition in the human respiratory tract (HRT) based on explicit hygroscopicity measurements at HRT-like conditions." Atmospheric Chemistry and Physics 22, no. 18 (September 21, 2022): 12387–99. http://dx.doi.org/10.5194/acp-22-12387-2022.
Full textAbstract:
Abstract. Particle hygroscopicity plays a key role in determining the particle deposition in the human respiratory tract (HRT). In this study, the effects of hygroscopicity and mixing state on regional and total deposition doses on the basis of the particle number concentration for children, adults, and the elderly were quantified using the Multiple-Path Particle Dosimetry model, based on the size-resolved particle hygroscopicity measurements at HRT-like conditions (relative humidity = 98 %) performed in the North China Plain. The measured particle population with an external mixing state was dominated by hygroscopic particles (number fraction = (91.5 ± 5.7) %, mean ± standard deviation (SD); the same below). Particle hygroscopic growth in the HRT led to a reduction by around 24 % in the total doses of submicron particles for all age groups. Such a reduction was mainly caused by the growth of hygroscopic particles and was more pronounced in the pulmonary and tracheobronchial regions. Regardless of hygroscopicity, the elderly group of people had the highest total dose among three age groups, while children received the maximum total deposition rate. With 270 nm in diameter as the boundary, the total deposition doses of particles smaller than this diameter were overestimated, and those of larger particles were underestimated, assuming no particle hygroscopic growth in the HRT. From the perspective of the daily variation, the deposition rates of hygroscopic particles with an average of (2.88 ± 0.81) × 109 particles h−1 during the daytime were larger than those at night ((2.32 ± 0.24) × 109 particles h−1). On the contrary, hydrophobic particles interpreted as freshly emitted soot and primary organic aerosols exhibited higher deposition rates at nighttime ((3.39 ± 1.34) × 108 particles h−1) than those in the day ((2.58 ± 0.76) × 108 particles h−1). The traffic emissions during the rush hours enhanced the deposition rate of hydrophobic particles. This work provides a more explicit assessment of the impact of hygroscopicity and mixing state on the deposition pattern of submicron particles in the HRT.
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Smellie, J. L., and I. L. Millar. "New K-Ar isotopic ages of schists from Nordenskjöld Coast, Antarctic Peninsula: oldest part of the Trinity Peninsula Group?" Antarctic Science 7, no. 2 (June 1995): 191–96. http://dx.doi.org/10.1017/s0954102095000253.
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K-Ar whole-rock dating of five samples of quartz-mica schist from the Nordenskjöld Coast, eastern Graham Land, provides the first unequivocal evidence of pre-Triassic (> 249 ± 7 Ma) deposition of a sequence regarded as part of the Trinity Peninsula Group (TPG). A maximum age range of latest Carboniferous (< c. 300 Ma)–Permian for deposition of the Nordenskjöld Coast sequence is indicated, and a polymetamorphic, polydeformational history for the TPG in northern Graham Land. However, the possibility exists that the rocks dated here from the Nordenskjöld Coast are part of a hitherto-unrecognized metamorphic basement unrelated to and older than the mainly Triassic TPG outcrops farther north. The new ages confirm the existence of a previously poorly-defined regional metamorphic event in the Antarctic Peninsula at about 245–250 Ma ago.
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Francis, Malcolm P., Steven E. Campana, and Cynthia M. Jones. "Age under-estimation in New Zealand porbeagle sharks (Lamna nasus): is there an upper limit to ages that can be determined from shark vertebrae?" Marine and Freshwater Research 58, no. 1 (2007): 10. http://dx.doi.org/10.1071/mf06069.
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Annual deposition of growth bands in vertebrae has been validated for many shark species, and is now widely regarded as the norm. However, vertebrae are part of the shark’s axial skeleton, and band deposition may stop in old sharks when somatic growth ceases. We aged vertebral sections from New Zealand porbeagle sharks (Lamna nasus) under reflected white light and using X-radiographs. Bomb radiocarbon assays supported vertebral age estimates up to ~20 years, but not at older ages. The results suggest that older porbeagles were under-aged by as much as 50% from vertebral band counts, presumably because band width declined to a point where it became unresolvable. This has important implications for growth studies on other long-lived sharks. Estimated ages at sexual maturity were 8–11 years for males and 15–18 years for females, and longevity may be ~65 years. New Zealand and North Atlantic porbeagles differ in these parameters, and in length at maturity and maximum length, suggesting genetic isolation of the two populations.
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Milgen, J. van, N. Quiniou, and J. Noblet. "Modelling the relation between energy intake and protein and lipid deposition in growing pigs." Animal Science 71, no. 1 (April 2000): 119–30. http://dx.doi.org/10.1017/s1357729800054941.
Full textAbstract:
AbstractWhen modelling the effect of a changing nutrient supply to growing animals, it is important to distinguish the individual response curve of an animal from the change in this response that may occur during growth. A data analysis model is proposed where, for an individual animal, the relation between protein deposition (PD) and metabolizable energy (ME) intake above maintenance (MEp) is curvilinear, so that PD intersects the origin and reaches its maximum at the maximum protein deposition rate (PDmax). An increase of MEp beyond that required to attain PDmax would not change PD. The MEp not used for protein synthesis can be used for lipid deposition (LD). The relation between PD and LD on the one hand and ME on the other hand can then be described as a function of the maintenance energy requirement (MEm), PDmax, the level of ME required to attain PDmax (F; as a multiple of MEm) and the energetic efficiencies of PD (kp) and LD (kf). Of these statistics, only kp and kf were assumed to be independent of body weight (BW), age or genotype. Variation in PDmax was described as a Gompertz function (of age) whereas variation in F was assumed a linear function of BW. Maintenance energy requirement was expressed as a power function of BW. To evaluate the model, 145 nitrogen and energy (indirect calorimetry) balances were obtained from three types of pigs (Large White castrated males (cLW) and Piétrain × Large White castrated males (cPP× ) and males (bPP×)) ranging in BW between 45 and 100 kg and housed under thermoneutral conditions. Animals were allotted to one of four energy levels ranging from 0·70 to 1·00 of ad libitum intake. The MEm was not different between genotypes (849 kJ/kg BW0·60) whereas the kp and kf were 0·56 and 0·75, respectively. For castrated animals on ad libitum intake, PDmax started limiting PD at approximately 130 days of age (78 and 86 kg BW for cLW and cPP×, respectively). Before this age and for bPP×, PD was limited by MEp. In bPP×, the difference between PD and PDmax was small (less than proportionately 0·05). The F did not change with BW for bPP× (2·85 × MEm) whereas for the other genotypes, it decreased linearly from 4·47 at 45 kg to 2·00 at 100 kg of BW. Due to its nature, the model allows estimation of PDmax even when energy is restricting PD.
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Hervé, Francisco, Víctor Faúndez, Manfred Brix, and Mark Fanning. "Jurassic sedimentation of the Miers Bluff Formation, Livingston Island, Antarctica: evidence from SHRIMP U–Pb ages of detrital and plutonic zircons." Antarctic Science 18, no. 2 (June 2006): 229–38. http://dx.doi.org/10.1017/s0954102006000277.
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Detrital zircon populations from two sandstone samples from the lower member (Johnsons Dock Member) of the Miers Bluff Formation at Hurd Peninsula have been dated by the Sensitive High Resolution Ion Microprobe (SHRIMP) U–Pb method. In one of the samples, zircons as young as early Middle Jurassic (Bajocian) age are present. In the second sample, the youngest detrital zircons are Middle Triassic in age. The detrital zircon age spectra indicate that Permian, early Palaeozoic and Meso- to Neoproterozoic zircon bearing rocks were present in the source areas of the Miers Bluff Formation. The sedimentary rocks are intruded by the Hespérides Point Intrusive diorite stock which yielded a U–Pb zircon crystallization age of 137.7 ± 1.4 Ma (Early Cretaceous, Valanginian). These results indicate that sedimentation of the Johnsons Dock Member of the Miers Bluff Formation is bracketed in time between the Bajocian and the Valanginian. The Miers Bluff Formation has been correlated with the Trinity Peninsula Group from the Antarctic Peninsula, based on sedimentological and structural similarity. Since the Trinity Peninsula Group is older than Middle Jurassic a direct chronological correlation is not supported by our new U–Pb zircon data. However, we suggest that the tectonic setting may have migrated in time with deposition of the pre-Middle Jurassic TPG on the peninsula, to Livingston Island where the maximum age for deposition of the MBF is Bajocian (about 170 Ma).
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Fan, Tianlai, Yuxin Fan, Hui Zhao, Fahu Chen, and Zhongping Lai. "Investigations on the degree of bleaching of quartz OSL signals using modern aeolian dust from western Loess Plateau, China." Geochronometria 40, no. 3 (September 1, 2013): 165–76. http://dx.doi.org/10.2478/s13386-013-0112-y.
Full textAbstract:
Abstract Optically Stimulated Luminescence signal of quartz extracted from modern aeolian dust with known maximum age (about decades) was analyzed in terms of degree of bleaching. The results of dose recovery tests show that the modified double single-aliquot regenerative-dose protocol with the early background subtraction is robust for dating these modern dusts using small aliquots. Bleaching of these dusts is discussed based on the distribution of De values in histograms, scatter plots of De versus sensitivity corrected natural OSL signal and comparison between measured De and expected De. The results indicate that most dusts were completely bleached but some dusts were not completely bleached. For those incompletely bleached dusts in Lanzhou area, the maximum OSL age overestimation is up to ∼1 ka, which might be caused by fast deposition accompanied by heavy sand/dust storms. The research suggests that cautions should be given to OSL ages younger than 1 ka in the western China close to deserts.
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Englert, R. G., S. M. Hubbard, W. A. Matthews, D. S. Coutts, and J. A. Covault. "The evolution of submarine slope-channel systems: Timing of incision, bypass, and aggradation in Late Cretaceous Nanaimo Group channel-system strata, British Columbia, Canada." Geosphere 16, no. 1 (December 16, 2019): 281–96. http://dx.doi.org/10.1130/ges02091.1.
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Abstract Submarine channel systems convey terrestrially derived detritus from shallow-marine environments to some of the largest sediment accumulations on Earth, submarine fans. The stratigraphic record of submarine slope channels includes heterogeneous, composite deposits that provide evidence for erosion, sediment bypass, and deposition. However, the timing and duration of these processes is poorly constrained over geologic time scales. We integrate geochronology with detailed stratigraphic characterization to temporally constrain the stratigraphic evolution recorded by horizontally to vertically aligned channel-fill stacking patterns in a Nanaimo Group channel system exposed on Hornby and Denman Islands, British Columbia, Canada. Twelve detrital zircon samples (n = 300/sample) were used to calculate maximum depositional ages, which identified a new age range for the succession from ca. 79 to 63 Ma. We document five phases of submarine-channel evolution over 16.0 ± 1.7 m.y. including: an initial phase dominated by incision, sediment bypass, and limited deposition (phase 1); followed by increasingly shorter and more rapid phases of deposition on the slope by laterally migrating (phase 2) and aggrading channels (phase 3); a long period of deep incision (phase 4); and a final rapid phase of vertical channel aggradation (phase 5). Our results suggest that ∼60% of the evolutionary history of the submarine channel system is captured in an incomplete, poorly preserved record of incision and sediment bypass, which makes up <20% of outcropping stratigraphy. Our findings are applicable to interpreting submarine channel-system evolution in ancient and modern settings worldwide and fundamentally important to understanding long-term sediment dispersal in the deep sea.
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Riggs, N. R., T. B. Sanchez, and S. J. Reynolds. "Evolution of the early Mesozoic Cordilleran arc: The detrital zircon record of back-arc basin deposits, Triassic Buckskin Formation, western Arizona and southeastern California, USA." Geosphere 16, no. 4 (June 30, 2020): 1042–57. http://dx.doi.org/10.1130/ges02193.1.
Full textAbstract:
Abstract A shift in the depositional systems and tectonic regime along the western margin of Laurentia marked the end of the Paleozoic Era. The record of this transition and the inception and tectonic development of the Permo-Triassic Cordilleran magmatic arc is preserved in plutonic rocks in southwestern North America, in successions in the distal back-arc region on the Colorado Plateau, and in the more proximal back-arc region in the rocks of the Buckskin Formation of southeastern California and west-central Arizona (southwestern North America). The Buckskin Formation is correlated to the Lower–Middle Triassic Moenkopi and Upper Triassic Chinle Formations of the Colorado Plateau based on stratigraphic facies and position and new detrital zircon data. Calcareous, fine- to medium-grained and locally gypsiferous quartzites (quartz siltstone) of the lower and quartzite members of the Buckskin Formation were deposited in a marginal-marine environment between ca. 250 and 245 Ma, based on detrital zircon U-Pb data analysis, matching a detrital-zircon maximum depositional age of 250 Ma from the Holbrook Member of the Moenkopi Formation. An unconformity that separates the quartzite and phyllite members is inferred to be the Tr-3 unconformity that is documented across the Colorado Plateau, and marks a transition in depositional environments. Rocks of the phyllite and upper members were deposited in wholly continental depositional environments beginning at ca. 220 Ma. Lenticular bodies of pebble to cobble (meta) conglomerate and medium- to coarse-grained phyllite (subfeldspathic or quartz wacke) in the phyllite member indicate deposition in fluvial systems, whereas the fine- to medium-grained beds of quartzite (quartz arenite) in the upper member indicate deposition in fluvial and shallow-lacustrine environments. The lower and phyllite members show very strong age and Th/U overlap with grains derived from Cordilleran arc plutons. A normalized-distribution plot of Triassic ages across southwestern North America shows peak magmatism at ca. 260–250 Ma and 230–210 Ma, with relatively less activity at ca. 240 Ma, when a land bridge between the arc and the continent was established. Ages and facies of the Buckskin Formation provide insight into the tectono-magmatic evolution of early Mesozoic southwestern North America. During deposition of the lower and quartzite members, the Cordilleran arc was offshore and likely dominantly marine. Sedimentation patterns were most strongly influenced by the Sonoma orogeny in northern Nevada and Utah (USA). The Tr-3 unconformity corresponds to both a lull in magmatism and the “shoaling” of the arc. The phyllite and upper members were deposited in a sedimentary system that was still influenced by a strong contribution of detritus from headwaters far to the southeast, but more locally by a developing arc that had a far stronger effect on sedimentation than the initial phases of magmatism during deposition of the basal members.
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Maurizot, P., D. Cluzel, S. Meffre, H. J. Campbell, J. Collot, and B. Sevin. "Chapter 3 Pre-Late Cretaceous basement terranes of the Gondwana active margin of New Caledonia." Geological Society, London, Memoirs 51, no. 1 (2020): 27–52. http://dx.doi.org/10.1144/m51-2016-11.
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AbstractThe basement under the Late Cretaceous unconformity in New Caledonia consists of three amalgamated terranes. They are all oceanic, arc-related and developed offshore from the eastern Gondwana active margin during periods of marginal basin development. Téremba Terrane is composed of deep sea Permian to Mesozoic arc-derived volcanic rocks and greywackes. The Koh–Central Terrane includes at its base an ophiolite with island arc tholeiites and boninites (Koh Ophiolite) of Late Carboniferous to Early Permian age overlain by a thick sequence of greywacke (Central Range Volcaniclastic Rocks) of Permian to Late Jurassic age. The Téremba Terrane and the Koh–Central Terrane may be part of the same forearc basin, with the rocks from the Koh–Central Terrane deposited in a deeper environment. The Boghen Terrane is a metamorphic complex composed of schists, broken formations and mafic–ultramafic mélange, derived from mixed terrigenous and volcanic sources. The overall fine grain size and laminar bedding suggest deep sea and more distal deposition than the other terranes. The maximum depositional ages from detrital zircons suggest deposition during the Early Jurassic to Early Cretaceous. The terrane is interpreted as a metamorphosed subduction complex that includes blueschist and greenschist facies metamorphic rocks exhumed through the Koh–Central Terrane. At a regional scale, the nature of these three pre-Late Cretaceous terranes confirms the existing palaeogeographical reconstructions, which locate New Caledonia outboard the ocean–continent subduction that surrounded Gondwana during the Paleozoic and Early Mesozoic. A detailed analysis of these terranes and their relationship with East Australian terranes of the same age shows that a marginal basin system probably existed between mainland Gondwana and proto-New Caledonia and closed before the Late Cretaceous. A tentative detailed reconstruction of this margin during the Carboniferous–Early Cretaceous period is proposed.
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Steelquist, A. T., G. E. Hilley, I. Lucchitta, and R. A. Young. "A constraint on post–6 Ma timing of western Grand Canyon (Arizona, USA) incision removed: Local derivation indicated by ca. 5.4 Ma fluvial deposits below Shivwits Plateau basalts north of Grand Canyon." Geosphere 17, no. 6 (October 1, 2021): 1704–14. http://dx.doi.org/10.1130/ges02353.1.
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Abstract The timing of integration of the Colorado River system is central to understanding the landscape evolution of much of the southwestern United States. However, the time at which the Colorado River started incising the westernmost Grand Canyon (Arizona) is still an unsettled question, with conflicting interpretations of both geologic and thermochronologic data from western Grand Canyon. Fluvial gravels on the Shivwits Plateau, north of the canyon, have been reported to contain clasts derived from south of the modern canyon, suggesting the absence of western Grand Canyon at the time of their deposition. In this study, we reassess these deposits using modern geochronologic measurements to determine the age of the deposits and the presence or absence of clasts from south of the Grand Canyon. We could not identify southerly derived clasts, so cannot rule out the existence of a major topographic barrier such as Grand Canyon prior to the age of deposition of the gravels. 40Ar/39Ar analysis of a basalt clast entrained in the upper deposit (in combination with prior data) supports a maximum age of deposition of ca. 5.4 Ma, limiting deposition to post-Miocene, a period from which very few diagnostic and dated fluvial deposits remain in the western Colorado Plateau. Analysis of detrital zircon composition of the sand matrix supports interpretation of the deposit as being locally derived and not part of a major throughgoing river. We suggest that the published constraint of <6 Ma timing of Grand Canyon incision may be removed, given that no clasts that must be sourced from south of Grand Canyon were found in the only known outcrop of gravels under the Shivwits Plateau basalts at Grassy Mountain north of Grand Canyon.
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Nielsen, Michael Houmark. "Extent and age of Middle and Late Pleistocene glaciations andperiglacial episodes in southern Jylland, Denmark." Bulletin of the Geological Society of Denmark 55 (February 23, 2007): 9–35. http://dx.doi.org/10.37570/bgsd-2007-55-02.
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New evidence on distribution and chronology of glaciations in southern Jylland is presented. Ten stratigraphic units including four till-formations have been identified in Middle- and Late Pleistocene sediment successions. The timing of successive glaciations and periglacial interludes based on luminescence dating is established for the past c. 200 kyr. The OSL-chronology predicts that deposition of Lillebælt Till (Late Saalian, Warthe Glaciation) occurred at 180-160 kyr. Deglaciation followed and barren periglacial environments existed until beginning of the Eemian. Periglacial conditions were restored c. 115 kyr ago and lasted well into the Middle Weichselian. Expansion of the Scandinavian Ice Sheet through the Baltic depression into southern Jylland caused deposition of Ristinge Klint Till (Ristinge Glaciation) c. 55–50 kyr ago. Glaciers flowed westwards beyond the Main Stationary Line (MSL) and may have terminated along ice showed ridges in the periglacially smoothed landscape east of the present North Sea coast. This traditionally named “Old Baltic”glaciation is now recognized elsewhere in the circum Baltic region besides Denmark. Deglaciation was succeeded by periglacial environments with cryoturbation, ice wedge growth, formation of wind abrasion pavements and low arctic habitats. Approaching the global glacio-eustatic low stand of the Last Glacial Maximum increased cooling and enhanced down slope creep caused widespread solifluction. In a sequence of Late Weichselian glacier advances, Mid Danish Till, East Jylland Till and Bælthav Till was deposited under progressing deglaciation between 25 and 18 kyr ago. Retarded melting of dead ice from the Ristinge Glaciation formed thermo karst depressions on the surfaceof outwash plains in front of MSL.
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Chen, Ya-Dong, Shoufa Lin, and Cees R. van Staal. "Detrital zircon geochronology of a conglomerate in the northeastern Cape Breton Highlands: implications for the relationships between terranes in Cape Breton Island, the Canadian Appalachians." Canadian Journal of Earth Sciences 32, no. 2 (February 1, 1995): 216–23. http://dx.doi.org/10.1139/e95-018.
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Cape Breton Island has been interpreted as consisting of four zones of pre-Carboniferous rocks, but the relationships among them are controversial. To help resolve the controversy, we have dated detrital zircons from a conglomerate (part of the Cheticamp Lake Gneiss) in the Aspy terrane in the northeastern Cape Breton Highlands using the U–Pb method. The following ages were obtained: 462 ± 2 Ma (Middle Ordovician); ~492–488 Ma (6 ages; Early Ordovician); 552 ± 3 Ma (latest Precambrian–Early Cambrian); 620 ± 13 and 687 ± 4 Ma (Cadomian); and 809 ± 17, 1423 ± 10, 1462 ± 12, 1605 ± 14, 1644 ± 4, and 1911 ± 5 Ma (Proterozoic). The Middle Ordovician age sets a maximum age limit for deposition of the conglomerate, and supports an Ordovician–Silurian age for the Cheticamp Lake Gneiss. The Early Ordovician, latest Precambrian–Early Cambrian, and Cadomian ages match published ages from the Bras d'Or terrane (and its correlatives) and the Mira terrane (and its correlatives), and indicate provenance of the conglomerate from both terranes. They also indicate that the Bras d'Or and Mira terranes had been connected by the time of deposition of the conglomerate. The combination of the Cadomian and the Proterozoic ages is typical of parts of South America, supporting a suggestion that the Avalon Composite Terrane was derived from South America.
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Al-Suwaidi, Ahmed S., and Sabah K. Aziz. "Sequence stratigraphy of Oxfordian and Kimmeridgian shelf carbonate reservoirs, offshore Abu Dhabi." GeoArabia 7, no. 1 (January 1, 2002): 31–44. http://dx.doi.org/10.2113/geoarabia070131.
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ABSTRACT Carbonate reservoirs on the eastern flank of the Oxfordian-Kimmeridgian intrashelf basin in offshore Abu Dhabi had received little attention until commercial oil accumulations in structural traps were discovered in the late 1980s and early 1990s. In order to clarify the geometric and chronostratigraphic relationships of the Oxfordian-Kimmeridgian reservoirs, a multidisciplinary study (seismic, lithobiofacies, geochemistry, strontium isotope dating, and well-log data) was used to develop a sequence stratigraphic model. After deposition of the Callovian upper Araej Formation, a differentiated carbonate platform was established in the early Oxfordian in offshore and western onshore Abu Dhabi. Tectonic subsidence coupled with sea-level fluctuations controlled the geometry, deposition, and distribution of the lithofacies. These ranged from organic-rich, limy mudstones in the basinal area, to porous and permeable bioclastic packstones, grainstones, and dolomites in shallow waters on the eastern flank of the intrashelf basin. The upper Kimmeridgian Arab-D Member of the Arab Formation overlies the basinal deposits. Three third-order Depositional Sequences were identified in the offshore area. They are named according to their contained Maximum Flooding Surface; a fourth sequence is an intermediate unnamed Depositional Wedge. Depositional Sequence Jurassic 50 is of Oxfordian age and was deposited during transgressive and highstand periods. The lower Kimmeridgian Depositional Sequence Jurassic 60 is a well-defined lowstand system tract overlain by short-lived transgressive and highstand system tracts. Overlying Depositional Sequence Jurassic 60 is the Depositional Wedge. Finally, Depositional Sequence Jurassic 70 consists of transgressive and highstand system tracts developed on an undifferentiated platform that had localized depressions in the west. The best reservoir developments are in highstand bioclastic packstones and grainstones below the type-1 sequence boundaries that cap Depositional Sequences Jurassic 50 and Jurassic 60. The reservoir units have porosities greater than 20 percent and permeabilities of more than 1,000 milliDarcies. The basinal facies of Depositional Sequence Jurassic 50 have the best source-rock potential in the intrashelf basin.
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Davies, Joshua H. F. L., Jörn-Frederik Wotzlaw, Alexander P. Wolfe, and Larry M. Heaman. "Assessing the age of the Late Cretaceous Danek Bonebed with U–Pb geochronology." Canadian Journal of Earth Sciences 51, no. 11 (November 2014): 982–86. http://dx.doi.org/10.1139/cjes-2014-0136.
Full textAbstract:
An ash-rich volcaniclastic sandstone immediately underlying dinosaur-rich material from the Danek Bonebed in the Horseshoe Canyon Formation (HCF), Edmonton, Alberta, Canada, contains accessory zircon, which have been dated employing U–Pb geochronology. Both laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and chemical abrasion isotope dilution thermal ionization mass spectrometry (ID-TIMS) U–Pb analyses have been conducted. The zircon age distributions are complex with U–Pb dates ranging from Precambrian to Cretaceous. We consider the youngest ID-TIMS 206Pb/238U date of 71.923 ± 0.068 Ma as the maximum deposition age of the ash-rich sandstone, placing the overlying Danek bonebed in the early Maastrichtian. This age is compatible with the paleontological assemblage from the Danek Bonebed and the regional stratigraphy. The zircon age distribution also implies that the HCF had a complex provenance of the detritus with some Archean and Proterozoic zircons, a group of Mesozoic, and a large compliment of Cretaceous grains. The results highlight the importance of high precision geochronology in constraining the age of important fossil deposits such as the Danek Bonebed.
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Spötl, Christoph, and Augusto Mangini. "U/Th age constraints on the absence of ice in the central Inn Valley (eastern Alps, Austria) during Marine Isotope Stages 5c to 5a." Quaternary Research 66, no. 1 (July 2006): 167–75. http://dx.doi.org/10.1016/j.yqres.2006.03.002.
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AbstractCalcitic flowstones are present in fractures of a Pleistocene breccia near Innsbruck, Austria, and record periods of carbonate precipitation in the unsaturated zone between 101,500 ± 1500 and 70,300 ± 1800 yr, constrained by U-series disequilibrium dates. The occurrence of these speleothems, their low carbon isotopic composition, and the lack of infiltrated siliciclastic material demonstrate that the central Inn valley – which harbored one of the most extensive valley glaciers during the last glacial maximum – was ice-free during Marine Isotope Stages 5c to 5a. Climatically warm periods are separated by distinct drops in the oxygen isotopic composition of the speleothem calcite, attributed to strong and possibly seasonally biased atmospheric cooling. During these intervening stadials, which mirror those identified in the Greenland ice cores and marine sea-surface temperature records, calcite deposition apparently came to a halt, but the Inn Valley remained ice-free. The youngest calcite layer formed between ∼74,000 and ∼70,000 yr and places a maximum age limit on the likely expansion of alpine glaciers during the Marine Isotope Stage 5/4 transition, consistent with other speleothem records.
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Holmden, C., and A. P. Dickin. "Paleoproterozoic crustal history of the southwestern Grenville Province: evidence from Nd isotopic mapping." Canadian Journal of Earth Sciences 32, no. 4 (April 1, 1995): 472–85. http://dx.doi.org/10.1139/e95-040.
Full textAbstract:
Nd isotopic mapping in the North Bay area of the Central Gneiss Belt, southwestern Grenville Province, has revealed the precise trend of a TDM model age line developed between the uplifted southern margin of the Archean Superior craton (TDM = 2.7 Ga) and a Paleoproterozoic allochthon (TDM = 1.9 Ga). Separating these two crustal blocks is a narrow zone of gneisses with intermediate TDM ages. These transitional gneisses are interpreted to reflect a remnant fault or ductile shear zone, of uncertain age, along which crustal material from both blocks mechanically mixed during their juxtaposition. Accordingly, the nature of the TDM line in the North Bay area is interpreted to be tectonic. In the Temiscaming area, widespread exposures of mature metasedimentary gneisses are shown by their TDM ages to be dominantly of Paleoproterozoic provenance. These results are consistent with the existing detrital zircon geochronology, inferring a maximum depositional age of ~1.7 Ga. The anorogenic chemistry of the North Bay orthogneiss and mixed calc-alkaline–alkaline chemistry of the Temiscaming gneisses suggest a connection between Paleoproterozoic anorogenic magmatism and synsedimentary quartzite deposition, which is a common association in 1.9–1.6 Ga accretionary orogens of southern Laurentia. The relatively close correspondence between widespread 1.9 Ga TDM ages and U–Pb crystallization ages as old as 1.74 Ga implies that rocks of the Central Gneiss Belt were originally the juvenile products of Paleoproterozoic orogenesis.
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Corfu, F., and R. P. Sage. "U–Pb age constraints for deposition of clastic metasedimentary rocks and late-tectonic plutonism, Michipicoten Belt, Superior Province." Canadian Journal of Earth Sciences 29, no. 8 (August 1, 1992): 1640–51. http://dx.doi.org/10.1139/e92-129.
Full textAbstract:
The study investigates the ages of clastic metasedimentary rocks and of late-tectonic alkalic to calc-alkalic intrusions and puts constraints on the timing of major deformation in the Michipicoten greenstone belt of the Wawa Subprovince. A trondhjemitic boulder in the Doré conglomerate of the southern metasedimentary belt is dated at 2698 ± 2 Ma. This is a maximum age of sedimentation that is also supported by ages of detrital zircons in the matrix and may directly reflect the time of synvolcanic deposition. Detrital zircons in metapsammites of the central and northern sedimentary belts yield younger ages of 2682 ± 3 and 2680 ± 3 Ma, respectively, suggesting that sedimentation occurred significantly later in the northern than in the southern parts of the greenstone belt. The ≤2682 Ma sedimentary rocks were affected by multiphase deformation that is related to the development of a large-scale recumbent fold and superimposed folds and faults. This tectonism was followed by the emplacement of the granodioritic Troupe Lake and Maskinonge Lake stocks that yield identical zircon and titanite ages of 2671 ± 2 Ma. The structurally older and deformed Herman Lake nepheline syenite has an imprecise titanite age of [Formula: see text]. The isotopic composition of Pb in feldspar of these intrusions is relatively evolved and, in light of geochemical considerations, may reflect provenance of the melts from enriched mantle reservoirs.