Eruption Age Research Articles

Testing less-conventional methods to date a late-pleistocene to Holocene eruption: Radiocarbon dating of paleosols and 36Cl exposure ages at Pelado volcano, Sierra Chichinautzin, Central Mexico

Despite their significance for estimating hazards and forecasting future activity, dating young volcanic deposits and landforms (<50,000 yrs old) remains a challenge due to the limitations inherent to the different isotopic chronometers used. The Trans-Mexican Volcanic Belt is one of the most active and populated continental arcs worldwide, yet its temporal pattern of activity is poorly constrained. Such deficiency is particularly problematic for the Sierra Chichinautzin Volcanic Field (SCVF) that is located at the doorstep of Mexico City and Cuernavaca and is hence a major source of risk for these cities. Existing ages for this area derive mostly from either radiocarbon on charcoal, which is rare and may be contaminated, or 40 Ar/ 39 Ar on rock matrix, which is poorly precise for this time period and rock type. Here, we focus on the Pelado monogenetic volcano, which is located in the central part of the SCVF and erupted both explosively and effusively, producing a large lava shield and a widespread tephra blanket. This unique eruptive event was previously dated at ∼12 calibrated (cal) kyrs BP, using radiocarbon dating on charcoal from deposits related to the eruption. To test alternative dating approaches and confirm the age of this significant eruption, we applied two less conventional techniques, radiocarbon dating of bulk paleosol samples collected below the complete tephra sequence at nine sites around the shield, and in-situ 36 Cl exposure dating of two samples of an aphyric lava from the base of the shield. Radiocarbon paleosol ages span a continuous time interval from 13.2 to 20.2 cal kyrs BP (2σ), except for one anomalously young sample. This wide age spread, along with the low organic contents of the paleosols, may be due to erosive conditions, related to the sloping topography of the sampling sites and the cool and relatively dry climate of the Younger Dryas (11.7–12.9 ka), during which the Pelado eruption probably occurred. The two 36 Cl-dated lava samples have consistent ages at 1σ analytical errors of 15.5 ± 1.4 ka and 13.2 ± 1.2 ka, respectively, yielding an average age of 14.3 ± 1.6 ka for this lava flow. The high full uncertainty in 36 Cl ages (24%) is due to high rock Cl content. We conclude that paleosol radiocarbon dating is useful if numerous samples are analyzed and climatic and relief conditions at the time of the eruption and at the sites of tephra deposition are considered. The 36 Cl dating technique is an alternative method to date volcanic eruptions, as it gave consistent results, but in the specific case of Pelado volcano, the high Cl content in the analyzed rocks increases the age uncertainties. • Catalogue of recent eruptions in Trans-Mexican Volcanic Belt is incomplete. • 14 C on paleosol and 36 Cl dating are used on a previously dated monogenetic volcano. • New ages are coherent with previous 14 C charcoal age. • Spread in paleosol ages likely due to erosive conditions at time of eruption. • 36 Cl ages are statistically consistent but poorly precise, due to high Cl in rock.

Eruption Timing and Sequence of Primary Teeth in a Sample of Romanian Children.

Teething is considered a significant event in the growth and development of the child by parents and especially by paediatric dentists and forensic scientists. They constantly need an “up-to-date mirror” of its variability for different geographic regions. The aims of the current study were to determine the timing and sequence of primary tooth emergence, and to establish a correlation between tooth eruption and general growth and external parameters in a sample of Romanian children. This study included 70 healthy children (53% girls and 47% boys), and the analysed data resulted from the questionnaires completed by parents during the whole process. General and specific data on primary teeth eruption were obtained. The differences between sexes were insignificant, except for the maxillary and mandibular canines (p = 0.047 and p = 0.018) and lower temporary second molars (p < 0.001), which were significantly increased in boys. The differences found between the two hemiarches were insignificant (p = 0.197). The mean age of eruption of the first tooth erupted was 7.07 ± 1.990 months. The unpaired t-test was used for comparison of the timings of eruption of the first primary teeth, according to the number of previous births and type of diet, and it was insignificant (p = 0.665 and p = 0.983 respectively).

Exploring the application of blue and red thermoluminescence for dating volcanic glasses

Tephras are significant markers in the stratigraphic record and play a key role in establishing paleoenvironmental and paleoclimate histories worldwide. Despite burgeoning research focused on tephra characterization and correlation techniques, there are still few techniques that allow for the direct dating of tephra, particularly below the lower age limit of K/Ar and Ar/Ar dating methods. In this study, we test different thermoluminescence (TL) dating approaches on the 4–11 μm volcanic glass constituents of three different independently different tephras. By comparing against independent age control, we demonstrate the utility of both blue (320–450 nm) and red (587–651 nm) TL emissions for dating volcanic glasses using single aliquot regenerative (SAR) dose techniques. We find that both blue and red TL emissions from the volcanic glass shards are dim but reproducible and show no evidence for significant sensitivity changes occurring between the natural TL and the first test dose during the SAR protocol. Fading tests on the blue TL signal show that g-values range from 1.6 ± 1.0 to 2.9 ± 1.1%/decade and are statistically indistinguishable with zero at 2σ for the red TL. Bleaching experiments show that both blue and red TL signals are sensitive to light exposure, with sensitivity corrected signals declining by ∼40% over a 2-h period. For all three tephras, both the fading-corrected blue and red SAR-TL ages are consistent with age expectation. These successful results demonstrate the effectiveness of TL techniques for determining the eruption ages of tephra deposits in primary position between ∼1 and at least 30 ka.

Improved age estimates for Holocene Ko-g and Ma-f~j tephras in northern Japan using Bayesian statistical modelling

The Ko-g and Ma-f~j tephras are two key isochronous marker layers in northern Japan, which are from the largest Plinian eruptions of Komagatake volcano (VEI = 5) and Mashu caldera (VEI = 6), respectively. Despite extensive radiocarbon studies associated with the two tephras, individual calibrated results show considerable variations and thus accurate ages of these important eruptions remain controversial. Bayesian statistical approaches to calibrating radiocarbon determinations have proven successful in increasing accuracy and sometimes precision for dating tephras, which is achieved through the incorporation of additional stratigraphic information and the combination of evidence from multiple records. Here we use Bayesian approaches to analyse the proximal and distal information associated with the two tephra markers. Through establishing phase and deposition models, we have taken into account all of the currently available stratigraphic and chronological information. The cross-referencing of phase models with the deposition model allows the refinement of eruption ages and the deposition model itself. Using this we are able to provide the most robust current age estimates for the two tephra layers. The Ko-g and Ma-f~j tephras are hereby dated to 6657-6505 (95.4%; 6586±40, μ±σ) cal yr BP, and 7670-7395 (95.4%; 7532±72, μ±σ) cal yr BP, respectively. These updated age determinations underpin the reported East Asian Holocene tephrostratigraphic framework, and allow sites where the tephra layers are present to be dated more precisely and accurately. Our results encourage further applications of Bayesian modelling techniques in the volcanically active East Asian region.

First evidence for Neoproterozoic rocks offshore South-East Greenland

AbstractMeta-sedimentary rocks recovered beneath Palaeogene basalts near the base of Ocean Drilling Program (ODP) Leg 152-917A offshore South-East Greenland were thought to be of Late Cretaceous age. This interpretation, however, has several inconsistencies as it requires a tectono-metamorphic event during the Cretaceous not recognized in the North Atlantic region, and the presence of a wide Mesozoic sedimentary basin that extended from SE-Greenland to the Rockall Plateau, for which there is currently no evidence. Here, we report a Neoproterozoic U/Pb apatite age of 905 ± 21 Ma and a younger 40Ar/39Ar isochron whole-rock age of 820 ± 40 Ma for an altered tuff layer that occurs in the upper part of the meta-volcaniclastic sequence recovered from hole 917A. The 40Ar/39Ar step-heating ages on biotite and whole-rock mini-cores from deeper in hole 917A yielded Palaeoproterozic dates that cluster around 1950 to 1850 Ma, pointing toward a Palaeoproterozoic source. The U/Pb apatite date is interpreted as the eruption age of the tuff layer, whereas the younger whole-rock 40Ar/39Ar age is consistent with low-temperature greenschist alteration of volcanic glass and secondary mineral growth during sedimentary burial in an extensional regime. The c. 905 Ma age for the tuff provides the first evidence for Neoproterozoic rocks offshore South-East Greenland and suggests a correlation between this sequence and the Torridon Group in the Hebridean Foreland of the Scottish Caledonides. The calc-alkaline nature of the volcaniclastic rocks and the age of the tuff layer point toward a source area with arc-magmatism related to the Renlandian event of the Valhalla Orogeny.

Age of eruption of the first permanent incisors varies between Merino genotypes and is related to liveweight

The eruption of the first permanent incisors in sheep determines the classification of lamb and hogget and impacts the sale value of animals in Australia. This study tested the hypothesis that the age of incisor eruption would differ between progeny from different Merino sires and would occur earlier for progeny that were heavier at 12 months of age. The study utilised wether progeny at a site in Western Australia from 29 sires born in 2016 (n = 347) or 2017 (n = 553), and ewe and wether (castrated male) progeny at a second site in New South Wales from 29 sires born in 2017 (n = 713 ewes and 343 wethers) or 2018 (n = 638 ewes and 457 wethers). Classing of incisor eruption commenced at 10–11 months of age and was recorded monthly until 19 or 20 months of age at the two sites. The average age of incisor eruption varied by up to 2.5 months between sire groups (P < 0.001) and incisor eruption was completed for all progeny within a sire group over three months for some sires but over 6 months for other sires. Incisor eruption occurred earlier for animals that were heavier at 12 months of age (P < 0.001). The period when animals gained weight up to 12 months also influenced incisor eruption, as differences in liveweight at weaning had twice the effect on age of incisor eruption compared with differences in liveweight gain post-weaning at both sites. Estimated stage of maturity at 12 months of age had minimal effects on subsequent age of incisor eruption, and regardless, the large variation in age of incisor eruption between sires were not accounted for by liveweight or stage of maturity at 12 months. In addition to selecting Merino sires that produce progeny that can be sold as lamb at an older age, farmers may also benefit from understanding the pattern of the first permanent incisors eruption specific to their genotype and monitoring liveweights and liveweight change to optimise the time and value of animals at sale.

No evidence for tephra in Greenland from the historic eruption of Vesuvius in 79 CE: implications for geochronology and paleoclimatology

Abstract. Volcanic fallout in polar ice sheets provides important opportunities to date and correlate ice-core records as well as to investigate the environmental impacts of eruptions. Only the geochemical characterization of volcanic ash (tephra) embedded in the ice strata can confirm the source of the eruption, however, and is a requisite if historical eruption ages are to be used as valid chronological checks on annual ice layer counting. Here we report the investigation of ash particles in a Greenland ice core that are associated with a volcanic sulfuric acid layer previously attributed to the 79 CE eruption of Vesuvius. Major and trace element composition of the particles indicates that the tephra does not derive from Vesuvius but most likely originates from an unidentified eruption in the Aleutian arc. Using ash dispersal modeling, we find that only an eruption large enough to include stratospheric injection is likely to account for the sizable (24–85 µm) ash particles observed in the Greenland ice at this time. Despite its likely explosivity, this event does not appear to have triggered significant climate perturbations, unlike some other large extratropical eruptions. In light of a recent re-evaluation of the Greenland ice-core chronologies, our findings further challenge the previous assignation of this volcanic event to 79 CE. We highlight the need for the revised Common Era ice-core chronology to be formally accepted by the wider ice-core and climate modeling communities in order to ensure robust age linkages to precisely dated historical and paleoclimate proxy records.

A rare case of transmigrated mandibular canine and combined orthodontic–surgical management

Canines are paramount teeth for esthetics and function. Transmigration of the lower permanent canine is a rare process of alteration of the eruption path toward the opposite part of the mandible. The position of the migrating tooth varies at different ages, so early detection of the tendency to cross the midline is crucial; canines that have already passed through the center of the mandible can be impossible to realign. Transmigration can start any time before the normal age of eruption. Comparing two radiographic images taken at different ages offers important diagnosis information. Camilleri & Scerri (2003) described a progressive alteration of the tooth position in four steps, from the normal appearance to a low position inside the corpus of the mandible. Following this classification, this article’s aim was to present a case of an impacted lower canine that was diagnosed between the second and third stage of transmigration, around the age of 10, and to detail the combined orthodontic–surgical treatment strategy for “recapturing” and the orthodontic mechanics used to align it. After the examination of cone-beam computed tomography, we have decided to use a lingual arch as a space maintainer and anchorage tool and to surgically expose the tooth. The canine’s initial position and the direction of the force of traction used allowed a proper alignment of the tooth inside the dental arch. The periodontal tissues management was important for good healing, stability, and aesthetics. The early detection allowed a proper interdisciplinary orthodontic–surgical management, and a successful outcome.

Relationship Between the Eruption of Third Molar Teeth and the Growing Status of the Assamese Inhabitants of a North-Eastern State of India.

ObjectivesEven though permanent teeth eruption time may vary, the tooth eruption stage represents a critical developmental milestone, which may help in the monitoring of the child's growing status towards adolescence. This paper aims to evaluate the relationship between the third molar eruption (TME) and investigate any possible association with the body mass index (BMI), which is used to monitor the growth of children and adolescents.MethodsWe included 1060 student participants aged 14 to 26 years from selected educational institutions in Assam for this study. We performed a conventional clinical dental examination to determine the stages of TME. Moreover, to calculate the individual height and weight, we have carried out a thorough physical examination to assess the BMI and rule out any visible congenital developmental anomalies.ResultThe overall mean age of the status of no eruption (NE), incomplete eruption (IE), and complete eruption (CE) categories of the third molar in the current research were 17.39±2.273, 18.67±2.282 and 20.33±2.566 years, respectively, and the difference in mean age was statistically significant (p-value <0.05). Among the 1060 participants assessed, 163 (15.38%) were underweight, 625 (58.97%) belonged to the average category, 207 (19.52%) were at risk of being overweight, and 65 (6.13%) were obese. The CE in both average and overweight categories was 109 (17.4%) and 37 (17.9%). Similarly, the NE status of the third molar in the underweight and obese category was 120 (73.6%) and 39 (60.0%), respectively. These differences in the frequency of TME in different BMI categories were found statistically significant (p-value <0.05).ConclusionThe result shows a substantial relationship between the mean age of eruption of third molar teeth and BMI among children and adolescents in 14 years to 26 years in the Assamese population. Further, the mean age can be used in forensic age determination.

Timing of clinical eruption of permanent teeth in children with molar incisor hypomineralization

Introduction/Objective. Molar incisor hypomineralization (MIH) is a developmental defect and it has a multifactorial etiology; there could be variations in dental eruptions in the children with this condition. The aim of this study was the comparison of the clinical eruption status of the permanent teeth in children with MIH and patients without MIH. Methods. The study group comprised a total of 300 children (176 females and 124 males aged 6?12 years) who had been diagnosed with MIH but had no systemic disease. The control group comprised 300 age- and sex-matched children without MIH. In the study and control groups, the eruption of the permanent teeth (excluding third molars) was evaluated and compared. In addition, this comparison was performed separately for the males and females in the study and control groups. The independent samples t-test was used for statistical analysis. Results. No statistically significant difference was found between the mean age of the dental eruptions of the children with MIH and that of the children without mineralization disorders (p &gt; 0.05). Regarding the mean age of the dental eruptions, the sex-matched comparison revealed no statistically significant difference between the study and control groups (p &gt; 0.05). Conclusion. Although there was no statistically significant difference in the MIH group and the healthy control group regarding the mean age of the eruption of all teeth, a trend of accelerated dental development in the MIH group was observed.

A multi-method approach to constrain the age of eruption and post-depositional processes in a Lower Jurassic ignimbrite from the Marifil Volcanic Complex, eastern North Patagonian Massif

In the eastern North Patagonian Massif, the Marifil Volcanic Complex corresponds to an Early Jurassic magmatic event. In this study, we evaluate new geochronological and thermochronological data obtained from an ignimbrite of the complex. U–Pb zircon ages from the pumice fraction reveal a Concordia age of 184.4 ± 1.1 Ma. Conversely, U–Pb zircon ages from the whole-rock sample evidence a Concordia age of 190.4 ± 0.6 Ma. Fission track techniques were applied on the same whole-rock sample. Zircon fission track performed on the same zircon-crystals dated by U–Pb yielded an age of 172.5 ± 8.1 Ma, while apatite fission track evidenced a cooling age of 179.1 ± 13.5 Ma. Apatite and zircon crystals describe uniform morphologies with unaltered euhedral to subhedral grains and well-developed crystalline forms. The results suggest that the age of eruption and deposition of the ignimbrite is better explained by the pumice zircon age rather than the whole-rock zircon age. Inherited grain-ages and petrographic evidence support provenance from older, probably cogenetic, magmatic products. Fission track ages reflect a post-depositional process probably related to diagenetic mineral changes.

Growth Stunting Implication in Children: A Review on Primary Tooth Eruption

AbstractGrowth stunting is a form of malnutrition that causes children to have a shorter height for their age. Growth stunting can affect tooth eruption, including delayed deciduous teeth eruption. An electronic search was performed in PubMed and Google Scholar up to December 2020 including the terms related to eruption time of deciduous teeth in stunted children, articles in English and Indonesian, research on humans, research articles, and articles that can be accessed in full text. Articles that were not related to eruption time of deciduous teeth in stunted children, articles published over the last 10 years, articles that only used weight for age indicator as an indicator of malnutrition, and articles with incomplete pages were excluded from the study. Seven cross-sectional articles were included in this study. Three studies assessed the age of deciduous teeth eruption, two studies assessed the number of erupted deciduous teeth in malnourished children, three studies assessed the sequence of deciduous teeth eruption, and six studies assessed the association of nutritional status with deciduous teeth eruption.

Mantle geodynamics and source domain of the East Vietnam Sea opening- induced volcanism in Vietnam and neighboring regions

The spreading of the East Vietnam Sea (EVS, also known as Bien Dong, or the South China Sea), leading to the occurrence of syn-spreading (33-16 Ma) and post-spreading (&lt; 16 to present) volcanism. Syn-spreading magma making up thick layers of tholeiitic basalt with a geochemical composition close to the refractory and depleted mid-ocean ridge basalt (MORB) is mainly distributed inside the EVS basin. The post-spreading magma is widely distributed inside the basin and extended to South and SE China, Hainan island, Southern Laos (Bolaven), Khorat Plateau (Thailand), and Vietnam, showing the typical intraplate geochemistry. Basaltic samples were collected at many places in Indochina countries, Vietnam’s coastal and continental shelf areas, to analyze for eruption age, petrographical, geochemical, and isotopic composition to understand the similarities and differences in the mantle sources between regions. The results reveal that basalts from some areas show geochemical features suggesting they were derived subsequently by spinel peridotite and garnet peridotite melting, forming high-Si, low-Mg, and low-Ti tholeiitic basalt to low-Si, high-Mg, and high-Ti alkaline basalt with the trace element enrichment increasing over time. Other basalts have geochemical and isotopic characteristics unchanged over a long period. The post-spreading basalt’s radiogenic Sr-Nd-Hf-Pb isotopic compositions show different regional basalts distribute in the various fields regardless of eruption age, suggesting that their mantle source feature is space-dependent. The post-EVS spreading basalts expose the regional heterogeneity, reflecting the mixture of at least three components, including a depleted mantle (DM) represented by the syn-EVS spreading source, similar to the DUPAL-bearing Indian MORB source; an enriched mantle type 1 (EM1), and type 2 (EM2). The DM may interact and acquire either EM1 or EM2 in the sub-continental lithospheric mantle; as a result, different eruption at different area acquires distinct isotopic signature, reflecting the heterogeneous nature of the subcontinental lithospheric mantle. The study proposes a suitable mantle dynamic model that explains the EVS spreading kinematics and induced volcanism following the India - Eurasian collision from the Eocene based on the research outcomes.

Origin of the tuff parting and associated enrichments of Zr, REY, redox-sensitive and other elements in the Early Miocene coal of the Siniy Utyes Basin, southwestern Primorye, Russia

Miocene coal beds in the Siniy Utyes Basin, South Primirye, in eastern Russia, are interbedded with volcanic ash layers and are enriched in rare earth elements and Y (REY, or REE if Y is not included), Zr, redox-sensitive and other trace elements around these layers. However, high contents of fresh volcanic glass and alkalies as well as no evidence of leaching suggest that the source of these elevated concentrations of these elements are not interpreted to be derived from the volcanic ash fall layers, as is found in many other coals worldwide. In contrast, the broader geochemical signature of the coal indicates that these elements sourced from weathered granites. Interestingly, both the coal and volcanic ash contain pyrite and, less commonly, barite, REE phosphate (rhabdophane?), silver sulfate and sylvite, all of which indicate a post-depositional emplacement of these trace elements, possibly through an initial evaporative process in the peat before burial. Instead of leaching of the adjacent tuff, enrichment of REY, Zr, Mo, V, and other elements in the coal proximal to the volcanic ash layers may be a result of higher permeability and a geochemical barrier at the coal/volcanic ash interface, which concentrated element migration in these zones during diagenesis. U-Pb zircon dating (LA ICP-MS) of the volcanic ash layer indicates an age in the 18–25 Ma range. The younger (5 of 22 grains) cluster of dates, however, is in the 18–19 Ma (early Miocene) range, which may indicate the age of the actual eruption.

The westernmost Late Miocene\u2013Pliocene volcanic activity in the Vardar zone (North Macedonia)

Late Miocene to Pleistocene volcanism within the Vardar zone (North Macedonia) covers a large area, has a wide range in composition, and is largely connected to the tectonic evolution of the South Balkan extensional system, the northern part of the Aegean extensional regime. The onset of the scattered potassic to ultrapotassic volcanism south from the Scutari-Peć transverse zone occurred at ca. 8.0 Ma based on this study. Here, we focused on three volcanic centers located on deep structures or thrust faults along the western part of the Vardar zone, for which there is none to very little geochronological and geochemical data available. Pakoševo and Debrište localities are represented as small remnants of lava flows cropping out at the southern edge of Skopje basin and at the western edge of Tikveš basin, respectively. Šumovit Greben center is considered as part of the Kožuf-Voras volcanic system, and it is located on its westernmost side, at the southern edge of Mariovo basin, which is largely composed of volcaniclastic sediments. We present new eruption ages applying the unspiked Cassignol-Gillot K–Ar technique on groundmass, as well as petrological and geochemical data, supplemented with Sr and Nd isotopes to complement and better understand the Neogene-Pleistocene volcanism in the region. Eruption ages on these rocks interlayered between sedimentary formations allow to better constrain the evolution of those sedimentary basins. Rocks from the three volcanic centers belong to the high-K calc-alkaline–shoshonitic series based on their elevated K content. The oldest center amongst these three localities, as well as other Late Miocene centers within the region, is the trachyandesitic Debrište, which formed at ca. 8.0 Ma, and exhibits the highest Nd and lowest Sr isotopic ratios (0.512441–0.512535 and 0.706759–0.706753, respectively). The basaltic trachyandesite Pakoševo center formed at ca. 3.8 Ma and its Nd and Sr isotopic ratios (0.512260 and 0.709593, respectively) bear the strongest signature of crustal contamination. The rhyolitic Šumovit Greben center is a composite volcanic structure formed at ca. 3.0–2.7 Ma. Its youngest eruption unit has a slightly higher Nd and lower Sr isotopic ratios (0.512382 and 0.709208, respectively) representing a magma with a lesser extent of crustal assimilation than the other samples from this center. The overall trend through time in the Sr and Nd isotopic ratios of the Late Miocene to Pleistocene mafic volcanic centers in the region implies an increasing rate of metasomatism of the lithospheric mantle.

The Medial Offshore Record of Explosive Volcanism Along the Central to Eastern Aegean Volcanic Arc: 2. Tephra Ages and Volumes, Eruption Magnitudes and Marine Sedimentation Rate Variations

AbstractWe use the tephrostratigraphic framework along the Aegean Volcanic Arc established in Part 1 of this contribution to determine hemipelagic sedimentation rates, calculate new tephra ages, and constrain the minimum magnitudes of (sub)plinian eruptions of the last 200 kyrs. Hemipelagic sedimentation rates range from ∼0.5 cm/kyr up to ∼40 cm/kyr and vary laterally as well as over time. Interpolation between dated tephras yields an eruption age of ∼37 ka for the Firiplaka tephra, showing that explosive volcanism on Milos is ∼24 kyrs younger than previously thought. The four marine Nisyros tephras (N1 to N4) identified in Part 1 (including the Upper (N1) and Lower (N4) Pumice) have ages of ∼57 ka, ∼63 ka, ∼69 ka, and ∼76 ka, respectively. Eruption ages for the Yali‐1 and Yali‐2 tephras are ∼55 ka and ∼34 ka, respectively. The Yali‐2 tephra comprises two geochemically and laterally distinct marine facies. The southern facies is identical to the Yali‐2 fall deposit on land but the western facies has slightly less evolved glass compositions. Overall, erupted plinian and co‐ignimbrite fall tephra volumes range from &lt;1 to 56 km3 (excluding possible caldera fillings and ignimbrite volumes), and 80% of the eruptions had magnitude 5.5 &lt; M ≤ 7.2 (M = log(m)‐7; m = erupted magma mass in kg). Twenty percent of the tephras represent 3.2 &lt; M &lt; 5.5 eruptions. The long‐term average tephra magma mass flux through highly explosive eruptions of Santorini is estimated at ∼40 kg/s. The analogous data for the Kos‐Yali‐Nisyros volcanic complex is less‐well constrained but similar to Santorini.

The Medial Offshore Record of Explosive Volcanism Along the Central to Eastern Aegean Volcanic Arc: 1. Tephrostratigraphic Correlations

AbstractThe Milos, Christiana‐Santorini‐Kolumbo (CSK) and Kos‐Yali‐Nisyros (KYN) volcanic complexes of the Aegean Volcanic Arc have repeatedly produced highly explosive eruptions from at least ∼360 ka into historic times and still show recent unrest. We present the marine tephra record from an array of 50, up to 7.4 m long, sediment cores along the arc collected in 2017 during RV Poseidon cruise POS513, which complements earlier work on distal to ultra‐distal eastern Mediterranean sediment cores. A unique set of glass‐shard trace element (LA‐ICPMS) compositions complements our major element (EMP) data on 220 primary ash layers and 40 terrestrial samples to support geochemical fingerprinting for correlations with 19 known tephras from all three volcanic complexes and with the 39 ka Campanian Ignimbrite from the Campi Flegrei, Italy. The correlations include 11 eruptions from CSK (Kameni, Kolumbo 1650, Minoan, Cape Riva, Cape Tripiti, Upper Scoriae 1 and 2, Middle Pumice, Cape Thera, Lower Pumice, Cape Therma 3). We identify a previously unknown widespread tephra from a plinian eruption on Milos (Firiplaka Tephra). Near the KYN we correlate marine tephras with the Kos Plateau Tuff, the Yali 1 and Yali 2 tephras, and the Upper and Lower Pumice on Nisyros. Between these two major tephras, we found two tephras from Nisyros not yet observed on land. The four Nisyros tephras form a systematic trend toward more evolved magma compositions. In the companion paper we use the tephrostratigraphic framework established here to constrain new eruption ages and magnitudes as a contribution to volcanic hazard assessment.

Age Estimation with Cemental Incremental Lines in Normal And Periodontally Diseased Teeth Using Phase Contrast Microscope

Background: Forensic age estimation defines an expertise in forensic medicine, which aimsto define in the most accurate way to determine the unknown chronological age of the personinvolved in judicial or legal proceedings. Dental cementum is a vital tissue which demonstratescontinuous apposition throughout the life of the tooth. Literature studies have revealed that toothcemental annulations(TCA) would serve as a reliable tool in establishing the age of an individual.The use of specialized microscopic methods are been employed to enhance the assessment ofthe cemental annulations. The study aims at assessment and evaluation of cemental annulationsin normal and periodontally diseased extracted teeth using phase contrast microscopic method.Methodology: A total of 60 teeth were included in the study and out of which thirty teeth were normaland 30 were periodontally involved teeth respectively. Longitudinal ground sections were prepared usingmicromotor and diamond disc. Sections were mounted and observed under phase contrast microscope.Measurements were made using an image analyzer software. The total width of cementum was dividedby the distance between two incremental lines. The eruption age of the tooth was then added to this toobtain the chronologic age for each individual. The results of the study showed no significant deviationof estimated age from the actual age in both periodontally sound and periodontally diseased teeth.Conclusion: The study concludes that the use of phase-contrast microscopy in conjunction with imageenhancement procedures improves the accuracy of age estimation and may serve as a reliable aid inforensic identification.

Age estimation with cemental incremental lines in normal and periodontally diseased teeth using phase contrast microscope: an original research

BackgroundAge estimation is an important factor in forensic science for human identification. Teeth are considered to play a vital role as they resist decomposition at death unlike other tissues. This resistance and the gradual structural changes that take place throughout the life of an individual have made teeth useful indicators for age estimation. Dental cementum shows continuous apposition throughout the life of an individual. Tooth cemental annulation is a microscopic method for the determination of an individual’s age based on the analysis of incremental lines of cementum. Light microscopy as well as specialized microscopic methods have been employed to enhance the assessment of the cemental annulations. Periodontal disease is the most common dental problem affecting millions of people. Assessing the efficiency of the tooth cemental annulations method in periodontally diseased teeth is an important requisite. This study aims at assessing and evaluating the tooth cemental annulations in normal and periodontally diseased teeth using phase contrast microscopic method for age determination.ResultsA total of 60 teeth were included in the study and out of which 30 teeth were normal (sound teeth without any associated pathologies) and 30 were periodontally involved teeth respectively. Longitudinal ground sections were prepared and observed under phase contrast microscope. Measurements were made using an image analyzer software. The total width of the cementum was divided by the distance between two incremental lines. The eruption age of the tooth was then added to this to obtain the chronologic age for each individual. The results in the present study showed that tooth cemental annulations are applicable to periodontally sound teeth as well as in periodontally diseased teeth. There was no significant difference of estimated age from the actual age in both periodontally sound and periodontally diseased teeth. Normal teeth showed a reliability value of 92% and periodontally compromised teeth showed 96% respectively. There was no substantial influence of periodontal health on the estimated age.ConclusionsThe study concludes that the use of phase contrast microscopy in conjunction with image enhancement procedures improves the accuracy of age estimation and may serve as a reliable aid in forensic identification.

Defining the Upper Nisyros Pumice (57.1 ± 1.5 ka) as new tephra isochrone for linking early MIS-3 palaeoenvironmental records in the Aegean-Black Sea gateway: New evidence from the Sea of Marmara

The rhyolitic Upper Nisyros Pumice (UNP) from the Kos-Yali-Nisyros volcanic system has been detected as a cryptotephra layer in lacustrine sediments from the Sea of Marmara (SoM). A new independent age of the UNP eruption at 57.1 ± 1.5 cal ka BP has been interpolated using a combination of radiocarbon dating, tephrochronology and wiggle-matching of the SoM proxy record (Ca-curves) with Greenland oxygen isotope data, therewith confirming recently published radioisotopic dates of UNP land deposits. The UNP tephra in the SoM was identified by comparisons of the SoM tephra glass chemical dataset with published data of other marine tephra records from the Aegean Sea and the Megali Limni lacustrine sediment sequence (Lesvos Island). The stratigraphic position of the UNP tephra in these records verified its deposition in the SoM at the onset of MIS-3 and specifically at the termination of Greenland Interstadial GI-16. The new findings define the UNP tephra as a valuable time marker for the synchronisation of palaeoenvironmental data for this time period and help spurring the establishment of a robust tephrostratigraphical framework for the last ∼70 kyr in the Aegean-Black Sea region.