Leiopathes glaberrima is a tall arborescent black coral species structuring important facies of the deep-sea rocky bottoms of the Mediterranean Sea that are severely stifled by fishing activities. At ...present, however, no morphological in vivo description, ecological characterization, age dating and evaluation of the possible conservation actions have ever been made for any population of this species in the basin. A dense coral population was reported during two Remotely Operated Vehicle (ROV) surveys conducted on a rocky bank off the SW coasts of Sardinia (Western Mediterranean Sea). L. glaberrima forms up to 2 m-tall colonies with a maximal observed basal diameter of nearly 7 cm. The radiocarbon dating carried out on a colony from this site with a 4 cm basal diameter revealed an approximately age of 2000 years. Considering the size-frequency distribution of the colonies in the area it is possible to hypothesize the existence of other millennial specimens occupying a supposedly very stable ecosystem. The persistence of this ecosystem is likely guaranteed by the heterogeneous rocky substrate hosting the black coral population that represents a physical barrier against the mechanical impacts acted on the surrounding muddy areas, heavily exploited as trawling fishing grounds. This favorable condition, together with the existence of a nursery area for catsharks within the coral ramifications and the occurrence of a meadow of the now rare soft bottom alcyonacean Isidella elongata in small surviving muddy enclaves, indicates that this ecosystem have to be considered a pristine Mediterranean deep-sea coral sanctuary that would deserve special protection.
Teen perceptions of adolescent dating violence Morrison, Katheryn E; Hymel, Shelley; Craig, Wendy ...
Journal of adolescence (London, England.),
10/2023, Letnik:
95, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Previous research shows that adolescents who experience dating violence most often disclose their victimization to a peer or friend, more so than to other sources of support. However, surprisingly ...little research has explored how adolescents respond to peer disclosures of dating violence. Addressing this gap, the present study assessed variations in adolescents' perceptions of blame, interpretations of the incident as violence, and intentions to respond across physical, psychological, sexual, cyber-psychological, and cyber-sexual dating violence scenarios.
As part of a national research project across Canada, 663 high school adolescents (432 girls, 65.2%) between the ages of 14-17 were randomly assigned to complete a questionnaire which included one of five different hypothetical dating violence scenarios. Next, participants responded to questions about their perceptions of the incident, as well as victim and perpetrator blame and responsibility, and their intentions to respond.
Results indicated that the type of dating violence experienced and the age and gender of participants all played a role in perceptions of blame, understandings of violence, and intentions to respond.
As one of the first studies to explore how adolescents perceived and responded to dating violence, considering both in-person and cyber forms of dating violence, this study fills an important gap in the literature. Findings underscore the uniqueness of cyber forms of dating violence and how pre/intervention programs must address the specific contexts and issues unique to each type of dating violence.
We present a new approach to laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) U‐Pb dating of carbonates based on selection and pooling of pixels from 2‐D elemental and isotopic ...ratio maps. This image mapping technique is particularly useful for targeting subdomains in samples with complex geological histories. Key major and trace elements that are sensitive to detrital components, postformational fluid ingress, mineralogical changes, or diagenetic overprinting are measured along with the Pb and U isotopic data. Laser sampling is undertaken along successive linear rasters that are compiled into maps using the Monocle add‐on for Iolite, with one pixel in the map corresponding to one time slice of the time‐resolved signal. These element, element ratio, and isotope ratio maps can be overlain over photomicrographs or scanning electron microscopy images to spatially link compositional data to textural and structural features. The pixels corresponding to likely homogeneous age domains can be isolated by applying appropriate selection criteria (e.g., Th < 0.3 ppm, Mg/Ca < 0.004) and pooled into pseudo‐analyses using a proxy for the parent/daughter ratio (e.g., 207Pb/235U, 238U/208Pb) to retrieve the largest possible spread of the data points on isochron diagrams. The approach is best suited for analytical setups capable of rapidly or simultaneously scanning over a large mass range and can yield a precision of ±1% or better on quadrupole instruments depending on U concentration, 238U/204Pb, and age of the sample. The sample‐specific filtering criteria for selection and rejection of data and their rationale can be reported, resulting in more transparency with regard to data processing.
Plain Language Summary
Carbonate minerals (the constituents of limestones, carbonate veins, and certain fossil shells) form in different environments and in response to different geological processes. Based on the radioactive decay of uranium to lead, the timing of these processes can be dated by measuring uranium and lead isotopes in carbonate minerals. However, this is often difficult to achieve because the uranium‐lead isotope system in carbonates is readily disturbed by later processes or events. Problems also arise if carbonate rocks contain detrital material or different generations of carbonate minerals or if they have unfavorable lead‐uranium ratios. Our approach to dating of carbonates involves mapping of polished rock fragments for key elements along with uranium and lead isotopes. The elemental and isotope maps can be precisely overlain over photomicrographs and other images to link the analytical data to textural and structural features of the sample. Pixels corresponding to specific chemical criteria can be selected from the maps to target areas that share likely similar formation conditions and age. Pooling of the selected pixels in pseudo‐analyses retrieves the largest possible spread in uranium‐lead ratios and helps improve the precision of the age. The approach assists in deriving and interpreting age information from complex carbonate samples.
Key Points
A new strategy for acquisition and processing of combined elemental and U‐Pb isotopic data for carbonate U‐Pb geochronology is presented
Image maps of time‐resolved analyses allow straightforward visual assessment of data in combination with structural and textural features
Selection and pooling of pixels from image maps assists in extraction of accurate and precise U‐Pb ages from likely homogeneous age domains
Precise and accurate U–Pb LA–ICPMS dating of many U-bearing accessory minerals (e.g. apatite, allanite, titanite and rutile) is often compromised by common Pb. LA–ICPMS dating of these U-bearing ...accessory phases typically requires a matrix-matched standard, and data reduction is often complicated by variable incorporation of common Pb not only into the unknowns but also particularly into the reference material. We present here a general approach to common Pb correction in U–Pb LA–ICP–MS dating using a modified version of the VizualAge U–Pb data reduction package for Iolite (VizualAge_UcomPbine). The key feature of the method is that it can correct for variable amounts of common Pb in any U–Pb accessory mineral standard as long as the standard is concordant in the U/Pb (and Th/Pb) systems following common Pb correction. Common Pb correction of the age standard can be undertaken using either the 204Pb, 207Pb or 208Pb(no Th) methods, and the approach can be applied to raw data files from all widely used modern multi-collector and single-collector ICPMS instruments.
VizualAge_UcomPbine first applies a common Pb correction to the user-selected age standard integrations and then fits session-wide “model” U–Pb fractionation curves to the time-resolved U–Pb standard data. This downhole fractionation model is applied to the unknowns and sample-standard bracketing (using a user-specified interpolation method) is used to calculate final isotopic ratios and ages. 204Pb- and 208Pb(no Th)-corrected concordia diagrams and 204Pb-, 207Pb- and 208Pb(no Th)-corrected age channels can be calculated for user-specified initial Pb ratio(s). All other conventional common Pb correction methods (e.g. intercept or isochron methods on co-genetic analyses) can be performed offline.
The approach was tested on apatite and titanite age standards (for which there are independent constraints on the U–Pb crystallization age) using a Thermo Scientific iCAP-Qc (Q–ICP–MS) coupled to a Photon Machines Analyte Excite 193nm ArF Excimer laser. Madagascar apatite, OLT1 titanite and R10 rutile were used as primary standards and were corrected for variable common Pb using the new VizualAge_UcomPbine DRS. The secondary Durango (31.44±0.18Ma) apatite standard yielded a U–Pb TW concordia intercept age of 31.97±0.59Ma (MSWD=1.09; primary standard corrected by the 207Pb-method) and a U–Pb concordia age of 31.82±0.40Ma (MSWD=1.4; primary standard corrected by the 204Pb-method). McClure Mountain (523.51±1.47Ma) yielded a U–Pb TW concordia intercept age of 524.5±3.7Ma (MSWD=0.72) while the Fish Canyon Tuff (28.201±0.046Ma) and Khan (522.2±2.2Ma) titanite standards yielded U–Pb TW concordia intercept ages of 28.78±0.41Ma (MSWD=1.4) and 520.9±3.9Ma (MSWD=4.2) respectively. The suitability of the 208Pb(no Th)-correction is demonstrated by the agreement between a U–Pb TW concordia intercept age of 452.6±4.7Ma (MSWD=0.89) and a 208Pb(no Th)-corrected TW concordia age of 448.6±4.5Ma (MSWD=1.4) on a c. 450Ma rutile which exhibits variable incorporation of common Pb.
A range of LA–ICPMS U–Pb dating applications are presented and include U–Pb dating of apatite from >3.8Ga gneisses from Akilia, SW Greenland. These apatites host 13C-depleted graphite inclusions that are interpreted as biogenic in origin and representing the oldest indications of life on Earth. The U–Pb age profiles on single apatite grains presented here are characteristic of Pb loss by volume diffusion with core–rim age differences of up to 300Ma. These data explain the scatter and poor precision of earlier U–Pb apatite age determinations on Akilia apatite. Other LA–ICPMS dating applications include U–Pb apatite dating as a rapid method for determining the age of mafic intrusions, U–Pb titanite and apatite dating of ash fall tuffs, determining temperature–time histories using multiple U–Pb thermochronometers and improving concordance in LA–ICPMS primary zircon standard datasets by analysing young, common Pb-bearing primary zircon standards that have not accumulated significant radiation damage.
•General approach to U–Pb LA–ICPMS dating of common Pb-bearing minerals using Iolite•The method can use any accessory mineral standard with variable amounts of common Pb.•Applications presented include U–Pb dating of apatite from >3.8Ga gneisses from Akilia, SW Greenland.•Improves concordance in U–Pb zircon dating by enabling analysis of young, common Pb-bearing primary zircon standards
The article reports the radiocarbon investigation results of the Lebombo Eco Trail tree, a representative African baobab from Mozambique. Several wood samples collected from the large inner cavity ...and from the outer part of the tree were investigated by AMS radiocarbon dating. According to dating results, the age values of all samples increase from the sampling point with the distance into the wood. For samples collected from the cavity walls, the increase of age values with the distance into the wood (up to a point of maximum age) represents a major anomaly. The only realistic explanation for this anomaly is that such inner cavities are, in fact, natural empty spaces between several fused stems disposed in a ring-shaped structure. We named them false cavities. Several important differences between normal cavities and false cavities are presented. Eventually, we dated other African baobabs with false inner cavities. We found that this new architecture enables baobabs to reach large sizes and old ages. The radiocarbon date of the oldest sample was 1425 ± 24 BP, which corresponds to a calibrated age of 1355 ± 15 yr. The dating results also show that the Lebombo baobab consists of five fused stems, with ages between 900 and 1400 years; these five stems build the complete ring. The ring and the false cavity closed 800-900 years ago. The results also indicate that the stems stopped growing toward the false cavity over the past 500 years.
In archaeological research, changes in material culture and the evolution of styles are taken as major indicators for socio-cultural transformation. They form the basis for typo-chronological ...classification and the establishment of phases and periods. Central European Bronze Age material culture from burials reveals changes during the Bronze Age and represents a perfect case study for analyzing phenomena of cultural change and the adoption of innovation in the societies of prehistoric Europe. Our study focuses on the large-scale change in material culture which took place in the second millennium BC and the emergence at the same period of new burial rites: the shift from inhumation burials in flat graves to complex mounds and simple cremation burials. Paul Reinecke was the first to divide the European Bronze Age (EBA) into two phases, Bz A1 and A2. The shift from the first to the second phase has so far been ascribed to technical advances. Our study adopted an innovative approach to quantifying this phenomenon. Through regressive reciprocal averaging and Bayesian analysis of radiocarbon-dated grave contexts located in Switzerland and southern Germany, we modelled chronological changes in the material culture and changes in burial rites in these regions in a probabilistic way. We used kernel density models to summarize radiocarbon dates, with the aim of visualizing cultural changes in the third and second millennium BC. In 2015, Stockhammer et al. cast doubt on the chronological sequence of the Reinecke phases of the EBA on the basis of newly collected radiocarbon dates from southern Germany. Our intervention is a direct response to the results of that study. We fully agree with Stockhammer's et al. dating of the start of EBA, but propose a markedly different dating of the EBA/MBA transition. Our modelling of radiocarbon data demonstrates a statistically significant typological sequence of phases Bz A1, Bz A2 and Bz B and disproves their postulated chronological overlap. The linking of the archaeological relative-chronological system with absolute dates is of major importance to understanding the temporal dimension of the EBA phases.
We present a petrological and geochronological study of the Proterozoic Mbuji-Mayi sedimentary Supergroup (Sankuru-Mbuji-Mayi-Lomami-Lovoy basin, Democratic Republic of the Congo) and of the ...overlying subvolcanic doleritic rocks. Dating this Supergroup in Central Africa is crucial to reconstruct the geological history and evolution of the Congo Basin and because it contains a large diversity of organic-walled microfossils including early eukaryotes. For this study, we use the Re–Os dating method on kerogen from shales from the top of the lower Group BI (which contains the microfossils) and Ar–Ar, Sm–Nd and U–Pb methods on the dolerites emplaced near the top of the succession, defining the end of the sedimentation in the basin. The 187Re/187Os dating yield an age of 1041 ± 58 Ma. For the dolerites, 40Ar/39Ar dating provide a similar minimum age from 1006 ± 13 to 1009 ± 32 Ma in the whole basin. 147Sm/143Nd dating confirms a less precise but overlapping age of 926 ± 170 Ma for sample from the Western part of the basin. Some 40Ar/39Ar dating and U–Pb dating provide also inherited Archean ages. The weighted average age for igneous samples from the basin is 1006 ± 12 Ma. This confirms that the upper Group BII was deposited from 1030 to 1040 to 1006 Ma, consistent with previous U–Pb dating on diagenetic minerals and with biostratigraphy. This new dating provides constraints on the late Mesoproterozoic – early Neoproterozoic diversification of early eukaryotes in Central Africa.
We also compare the petrology, geochemistry and geochronology of dolerites from different locations of the basin. Our new data evidence a common origin for all the subvolcanic rocks, emplaced in an intraplate setting and intruding the Archean basement, and indirectly date the end of the extensional stage that initiated the development of the Congo Basin.
•Dating on different dolerites from the SMLL basin provides a similar age around 1.0 Ga.•This study furnishes informations on the Congo Basin geodynamics.•These new ages provide constraints on the diversification of eukaryotes in Central Africa.
Multichronological data reveal the thermotectonic history of the northern Kyrgyz Tien Shan granitoids (Kyrgyzstan) from emplacement to exhumation. Zircon SHRIMP and LA-ICP-MS U/Pb concordia ages ...suggest a Middle to Late Ordovician crystallization age (440–470
Ma) for the most voluminous; Caledonian intrusion phase, which is associated with the evolution and closure of the Early Palaeozoic Terskey Ocean. The presence of some additional Early Ordovician – Cambrian U/Pb ages point towards a prolonged production of granitoids during the entire Early Palaeozoic. A sampled younger granitoid (292
±
5
Ma) was formed during the final closure of the Turkestan Ocean when Tarim eventually collided with the Kazakhstan plate during Hercynian orogeny.
40Ar/
39Ar step-wise heating plateau-ages (biotite Ar/Ar: 400–440
Ma; K-feldspar Ar/Ar: 235–375
Ma) bear witness to rapid Silurian – Early Devonian post-magmatic cooling of the Caledonian intrusives, followed by a more modest rate of cooling during the Late Devonian until the Late Triassic. Low-temperature techniques such as apatite fission track (AFT) and Apatite (U–Th–Sm)/He (AHe) thermochronology, give Late Jurassic – Cretaceous ages (90–160
Ma) with some Cenozoic outliers. Thermal history modelling allows us to distinguish two marked cooling phases: (1) Mesozoic cooling occurred as the result of denudation and exhumation of the Tien Shan basement during a pulse of tectonic reactivation, associated with the Cimmerian orogeny. (2) Late Cenozoic cooling (∼10–3
Ma) reflects a far-field effect of the India–Eurasia collision. Some samples also experienced a Late Oligocene – Miocene reheating event, which could be the result of burial due to sediment load stripped from the adjacent, eroding mountain ranges.
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