Isotope Chronologies Research Articles

Early generation of a refractory inclusions-enriched H-chondritic parent body: A safe harbor for Ca, Al-rich inclusions

Calcium-aluminum-rich inclusions (CAIs) commonly observed in chondritic meteorites are the oldest dated solids formed in the Solar System. Short-lived isotope chronologies (26Al-26Mg, 182Hf-182W) suggest a ∼2 Ma gap between the formation of CAIs and the accretion of the final chondrite parent bodies. One thin section, 3.27 cm2 in size, of an ordinary chondrite NWA 3358 (H3.1) studied contains 52 refractory inclusions (CAIs and amoeboid olivine aggregates (AOAs)) comprising 0.14 % of its area, which is the highest abundance of refractory inclusions among non-carbonaceous chondrites containing on average ∼0.009 area % of CAIs and AOAs. In combination with a low chondrule/matrix ratio of ∼1.5, this makes NWA 3358 a unique ordinary chondrite. The aqueously-formed fayalites (Fa>99) in NWA 3358 have the inferred initial 53Mn/55Mn ratio of (5.56 ± 0.44) × 10−6 which is the highest measured value for secondary minerals in chondrites and corresponds to the formation time of ∼1.0–1.5 Ma after CAIs. Based on the 53Mn-53Cr chronology of fayalite formation and the thermal modeling, we infer that the first-generation of an H chondrite parent body, ∼6–12 km in diameter, accreted within 1.0 Ma after formation of CAIs, filling the gap of ∼2 Ma between CAIs and the earliest chondrite parent bodies. This early accretion provides a possible mechanism of CAIs/AOAs storage in the inner solar nebula and could explain the high amount of refractory inclusions in NWA 3358. A later destruction of these first-generation bodies may also explain the presence of CAIs and chondrules of different ages within later formed chondrite parent bodies.

Methodological constrains of tree-ring stable isotope chronologies

Tree-ring stable isotope (TRSI) chronologies that combine information from living and relict wood have the potential to capture long-term trends that might be missing in traditional tree-ring width and maximum latewood density measurements. Our understanding of the possible effects of different methods to develop TRSI chronologies is, however, still incomplete. Here, we compare and evaluate five such methods applied to three multi-millennial-long oxygen isotope (δ18O) TRSI datasets from central Europe, the European Alps and Japan: (a) raw data, (b) cohort correction, (c) interactive mean correction, (d) outlier correction, and (e) series normalization. We show that the spectral properties preserved in the final TRSI chronologies not only depend on the data used, but also on the techniques applied. Method (a) is particularly prone to outliers if the sample size is low. Method (b) may create artificial steps and trends when single measurement series share similar start dates and/or when end and start dates are systematically skewed. Methods (c) and (d) yield similar results for annually resolved data, yet (d) is more suitable for temporally pooled datasets and less sensitive to potential biological age effects. Method (e) removes any low-frequency signal. Our findings demonstrate the risks and rewards of different TRSI chronology development techniques that must be carefully adapted to both, the data used and the question posed.

Multiproxy tree ring reconstruction of glacier mass balance: insights from Pinus cembra trees growing near Silvretta Glacier (Swiss Alps)

Abstract. Glacier mass balance reconstructions provide a means of placing relatively short observational records into a longer-term context. Here, we use multiple proxies from Pinus cembra trees from God da Tamangur, combining tree ring anatomy and stable isotope chronologies to reconstruct seasonal glacier mass balance (i.e., winter, summer, and annual mass balance) for the nearby Silvretta Glacier over the last 2 centuries. The combination of tree ring width, radial diameter of earlywood cell lumina, and latewood radial cell wall thickness provides a highly significant reconstruction for summer mass balance, whereas for the winter mass balance, the correlation was less significant but still robust when radial cell lumina were combined with δ18O records. A combination of the reconstructed winter and summer mass balances allows the quantification of the annual mass balance of the Silvretta Glacier for which in situ measurements date back to 1919. Our reconstruction indicates a substantial increase in glacier mass during the first half of the 19th century and an abrupt termination of this phase after the end of the Little Ice Age. Since the 1860s, negative glacier mass balances have been dominant and mass losses accelerate as anthropogenic warming picks up in the Alps.

Seasonal and Depth Dynamics of Soil Moisture Affect Trees on the Tibetan Plateau

The soil moisture (SM) influences tree growth with climate change. However, the spatial and temporal dynamics of tree water use strategies in climate-sensitive areas remain uncertain. Therefore, we collected the tree-ring oxygen isotope (δ18OTR) chronologies and divided the wet–dry gradients according to the precipitation on the Tibetan Plateau (TP). Further, the relationship between the δ18OTR and environmental factors was analyzed across different gradients. We found the following: (1) The SM during the growing season was the most important factor for δ18OTR. (2) The response of the δ18OTR to the SM had a lag in arid areas than in humid areas. (3) Trees absorbed the SM on the surface in humid areas (r = −0.49 to −0.41, p < 0.01), while trees absorbed the SM from deep in the soil in arid areas (r = −0.48 to −0.29, p < 0.01). The results demonstrated that trees were better able to cope with drought stress in arid regions because they used more stable deep soil water than in humid regions. Therefore, the findings will provide a scientific basis for water use of trees using the δ18OTR in complex environmental contexts. Trees with single water use strategies should be given more attention to keep ecosystems healthy.

Summer climate information recorded in tree-ring oxygen isotope chronologies from seven locations in the Republic of Korea

The Republic of Korea is characterized by its north-to-south stretch and high mountain ranges along the eastern coast, resulting in terrain with higher elevation in the east and lower in the west. These geographical features typically lead to regional climate differences, either based on latitude or from east to west. In the present study, for effectiveness, the entire Korean peninsula was divided into four regions based on the geographical features: The Northeast Coast (NEC), Central Inland (MI), Southeast Coast (SEC), and South Coast (SC). Two test sites were chosen from each region, except for the SC. The linear relationship between the altitude of sites and the mean oxygen isotope ratio (δ18O) revealed a negative correlation; the highest (1,447 m a.s.l.) and the lowest altitude (86 m a.s.l.) sites had a mean δ18O of 27.03‰ and 29.67‰, respectively. The sites selected from the same region exhibited stronger correlation coefficients (0.75–0.79) and Glk (Gleichläufigkeit) (74–83%) between the tree-ring oxygen isotope chronologies (δ18OTR chronologies) than those from different regions (0.60–0.69/70–79%). However, subtle variations in pattern were observed in the comparison period during a few selected intervals (approximately 10 years). All the regional δ18OTR chronologies exhibited positive correlations with either June or July temperatures over Korea, whereas negative correlations with regional summer precipitation and SPEI-3. Moreover, the chronologies showed notable negative correlations with the water condition of western Japan. The findings of this study can be used as a scientific reference for the study of variations of rainfall in East Asia using δ18OTR chronology.

Discovery of abundant shock-induced metallic lead nanograins in lunar zirconolite

The behaviors of radiogenic Pb in Zr-minerals are critical for reconstructing the chronological framework for the evolutionary history of our Earth and other planetary bodies. Previous investigations have revealed the presence of Pb nanograins in some terrestrial zircons and attributed it to radiation decay of U and mobilization and accumulation in zircon and a subsequent thermal metamorphic event. However, whether impact, a ubiquitous and fundamental process for the evolution of materials on planetary surfaces, can directly produce Pb nanograins in Zr-minerals remains unknown. Here, we report the discovery of abundant metallic Pb nanograins in zirconolite polycrystalline aggregates in the brecciated lunar meteorite Northwest Africa 8182. We propose that the metallic Pb nanograins and their host zirconolite polycrystalline aggregates formed during shock lithification of the host meteorite, which had a significant impact on micro-scale U-Pb isotopic chronology of shocked Zr-minerals. The formation of metallic Pb nanograins also indicates that a reduction of PbO took place during shock metamorphism.

SQUEAKY CLEAN CELLULOSE: COMPARING PRETREATMENT EFFECTIVENESS ON SINGLE TREE RINGS AND WOODEN LATHS

ABSTRACT Obtaining accurate radiocarbon (14C) results from wood samples requires the extraction of cellulose. In the past, this has been done using different combinations of methods including acidified bleaching, acid-base-acid, and strong bases. This often becomes a time-consuming task in most analyses, especially when single ring isotope chronologies are needed from wood samples. Using 14C and Fourier-transform infrared spectroscopy (FTIR), we tested four different pretreatment methods to determine their ability to produce high quality cellulose. We then adjusted the best methods to determine a method for pretreating wood laths of multiple rings. A sequence of base-acid-base-acid-bleach + strong base (BABAB+) and BABAB produced the most accurate results when compared to the Bomb20 Northern Hemisphere Zone 1 curve with an average difference in Δ14C of 1.3‰ and 5.8‰ respectively. These methods were adjusted to pretreat an entire wood lath and a comparison of the FTIR results suggest that our adjusted BABAB+ and BABAB produced high quality cellulose comparable to that of an individually pretreated ring. The possibility to pretreat wood lath samples has the potential to more than double the number of tree rings which can be pretreated in a week. This is a significant reduction in time when creating long tree ring chronologies.

Drought, temperature, and moisture availability: understanding the drivers of isotopic decoupling in native pine species of the Nepalese Himalaya.

The Himalayas experienced long-term climate changes and recent extreme weather events that affected plant growth and the physiology of tree species at high-elevation sites. This study presents the first statistically robust δ18OTR chronologies for two native pine species, Pinus roxburghii, and Pinus wallichiana, in the lower Nepalese Himalaya. The isotope chronologies exhibited 0.88‰ differences in overall mean isotope values attributed to varying elevations (460-2000m asl). Comparative analysis of climate response using data sets from different sources and resolutions revealed the superiority of the APHRODITE (Asian Precipitation - Highly-Resolved Observational Data Integration Towards Evaluation) data set calibrated for the South Asian Summer Monsoon (SASM)-dominated region. Both species exhibited negative correlations with monsoon precipitation and positive correlations with temperature. However, during the peak monsoon season (July-August), daily resolved climate data disentangled statistically insignificant relationships, and revealed that δ18OTR is influenced by atmospheric moisture. Both congeneric species showed a decoupling between the chronologies after 1995. However, no significant change in air moisture origin and monsoon regime between the study sites was observed, indicating a consistent dominant moisture source during different monsoon seasons. Besides, we also observed the decreased inter-series correlation of both δ18OTR chronologies after 1995, with P. wallichiana experiencing a steeper decrease than P. roxburghii. The weakening correlations between and within the chronologies coincided with a regional drought during 1993-1995 in both sites, highlighting the strong regulation of local climate on the impact of regional extreme climate events. Our findings emphasise the importance of employing climate data with optimal spatial and temporal resolution for improved δ18OTR-climate relationships at the intra-annual scale while considering the influence of site-specific local environmental conditions. Assessing climate data sets with station data is vital for accurately interpreting climate change's impact on forest response and long-term climate reconstructions.

Ore-forming age and material sources of the North Santonggou manganese deposit in East Kunlun of Qinghai: Constrained by Re-Os isotopic chronology and geochemistry

Ore-forming age and material sources of the North Santonggou manganese deposit in East Kunlun of Qinghai: Constrained by Re-Os isotopic chronology and geochemistry

Mediterranean water in the Atlantic Iberian margin reveals early isolation events during the Messinian Salinity Crisis

Recent studies highlight the role of the Mediterranean Outflow Water (MOW), in the intensification of the Atlantic Meridional Overturning Circulation and as source of heat and salty water to high latitudes. During the Late Miocene the MOW suffered major changes and likely a total collapse during the Messinian Salinity Crisis (MSC). In order to study the MOW evolution in the Atlantic margin during the Tortonian-Messinian interval we completed a new high resolution geochemical and stable isotope record for the corresponding interval of the Montemayor-1 and Huelva-1 cores. Both sites are located in the Guadalquivir Basin on the former Atlantic side of the Mediterranean – Atlantic gateways (Iberian Atlantic margin) during the late Miocene. The tuning of this isotope record with astronomical solutions and other global isotope curves has allowed the establishment of an improved chronology and, consequently, to precisely date environmental changes happening on the Atlantic margin of the Iberian peninsula and their link to Mediterranean and global events. At 7.17 Ma, in concomitance with a shallowing of the basin, the residence time, temperature and salinity of the bottom waters increased. These changes were related to a reduction of the MOW reaching the Atlantic side as a consequence of the restriction of the last strand of the Betic corridor that connected the Mediterranean and the Atlantic. This hypothesis is in line with the analogous changes observed in several Mediterranean Sea locations, where from 7.17 Ma onward a reduced Mediterranean – Atlantic connection is observable. Furthermore, the new isotope chronology sheds light, through comparison with other records, on the age of Messinian geomagnetic reversals.

Stable isotopes in eye lenses reveal migration and mixing patterns of diamond squid in the western North Pacific and its marginal seas

Abstract Knowledge of the movements of marine organisms is essential for effective conservation schemes. Here, we investigated the lifetime habitat use of diamond squid, Thysanoteuthis rhombus, collected in the western North Pacific and its marginal seas (the Sea of Japan and the East China Sea) during 2021–2022, whose migratory ecology is poorly known, using bulk stable nitrogen and carbon isotope ratios in eye lenses. From the eye lens isotope profiles, the chronology of the isotopic baseline of squid habitat was estimated by removing the effect of size-dependent changes of trophic position. Then, the baseline estimates were compared to the isoscapes of particulate organic matter. The baseline chronologies showed fluctuations during the paralarval and juvenile stages, becoming stable during the adult stage, suggesting that significant movements mainly occur during the early life stages due to current transport, with adults potentially not undertaking long-distance migrations. The squids in the marginal seas mostly originated from outside the subtropical gyre, while the squids in the subtropical gyre had various sources, including outside the gyre and southern and northern parts within the gyre, revealing a complex mixing pattern of the species. These results show that isotope chronology combined with baseline isoscapes are effective tools to understand animal migrations, which can help managing various cephalopods and fish.

Petrogenesis and Geochronology of the Shazuoquan Ophiolite, Beishan Orogenic Belt: Constraints on the Evolution of the Beishan Ocean

The ophiolites in the Beishan Orogenic Belt provide important information about the evolution of the Beishan Ocean in the Paleozoic Era. We studied ophiolite petrology, geochemistry and isotopic chronology. The Shazouquan ophiolites consist of dunites, wehrlites, gabbros and anorthosites. Ophiolitic mélange belts are composed of matrixes and blocks, and different rocks are fault-bounded. Dunites and wehrlites are high in Mg#, Cr# and MgO, low in TiO2, relatively depleted in large-ion lithophile elements (Ti and P) and enriched in high-strength elements (U, Zr and Hf). They have a total REE of 1.25 × 10–6−5.39 × 10−6 and δEu of 1.12–3.54, which are similar to those of SSZ-type ophiolites, indicating that their parent magma source region may be a weakly depleted mantle source region. The anorthosite and gabbro are high in Al2O3, MgO and Mg#, low in TiO2, enriched in large-ion lithophile elements (Rb and Sr), and depleted in high-strength elements (Nb, Ta and Ti), but enriched in Zr and Hf. They have similar geochemical signatures to those of arc magmatic rocks. They are derived from the mantle peridotite formed against the tectonic background of subduction and modified by the fluid materials in the subduction zone. We collected anorthosite and gabbro, which were produced as ophiolite for U-Pb dating. The anorthosite yields a zircon U-Pb, aged 394 ± 11 Ma (MSWD = 0.84), and a gabbro zircon U-Pb, aged 466 ± 12 Ma (MSWD = 3.2), indicating that the Shazouquan ophiolite was formed in the Middle Ordovician–Early Devonian eras. Combining the above evidence, we conclude that the Beishan Ocean was in a subduction tectonic background from the Middle Ordovician to Early Devonian periods.

Zircon U-Pb chronology and geochemistry of porphyritic granites: A case study of the Dalancun granites in Zhaoyuan, Shandong Province

The granite in Dalancun, Zhaoyuan, Shandong Province is mainly porphyry granite. In this paper, detailed field geology, petrology, isotopic chronology and whole-rock principal and microgeochemistry have been studied. LA-ICP-MS zircon U-Pb chronology shows that it was formed in the Early Cretaceous (129.7 ± 0.8 Ma), later than Linglong granite (160-150 Ma) and earlier than Laoshan granite (120-114 Ma). It is consistent with the main ore-forming age of Jiaodong large gold deposit and the diagenetic age of Guojialing granite (130-126 Ma). K2O+Na2O=7.41%~9.37%, K2O/Na2O=0.78~1.24; A/CNK=0.89~1.06, MgO=0.63%~1.01%, with high K, Al characteristics, belongs to the quasi-aluminum-peralumin high potassium calc-alkaline series. The strong differentiation of rare earth elements (La/Yb) N=68.24~93.96, weak positive Eu anomaly (δEu=1.26~1.769), enrichment of large ion lithophile elements Ba, Sr, high field strength elements Nb, Ta, Ti deficit, indicating the geochemical characteristics of continental lithosphere. In addition, high Sr (1817×10-6~2017×10-6), low Y (7.55×10-6~9.36×10-6), Sr/Y ratio between 199.89~262.29, Nb/Ta ratio between 14.67~16.73, consistent with continental crust ratio, It shows the characteristics of type I granite and Adakite. Combined with other geochemical indexes and regional geological studies, this paper suggests that the Dellancun porphyritic granite belongs to crust-mantle granite, which may have been formed in the arc environment of continental margin during the transition from compressive to extensional tectonic system in Jiaodong area, and is closely related to the subduction of the paleo-Pacific plate. This study not only helps to understand the Mesozoic tectonic evolution in eastern China, but also provides a basis for revealing the formation mechanism of Jiaodong gold deposit.

Differences in the Responses of Tree-Ring Stable Carbon Isotopes of L. sibirica and P. schrenkiana to Climate in the Eastern Tianshan Mountains

The eastern Tianshan Mountains are located in the arid interior of Asia, where tree growth is especially sensitive to climate. The ratio of stable carbon isotopes (δ13C) in the tree rings can provide information on changes in atmospheric CO2 concentrations, water availability, and physiological processes within the tree. In particular, the use of tree-ring δ13C values as a proxy for past atmospheric CO2 concentrations has gained widespread acceptance. In this study, detrended stable carbon isotope chronologies (13Ccorr) of Larix sibirica Ledeb. and Picea schrenkiana Fisch. et Mey was established using tree-ring samples from high elevations in the eastern Tianshan Mountains of Xinjiang, China. The relationships between the tree-ring 13Ccorr and different climatic factors were explored using the correlation function and collinearity analysis. Our results demonstrate that the tree-ring δ13Ccorr of L. sibirica is significantly and negatively correlated with precipitation and relative humidity during the growing season. The main climate factor affecting the stable carbon isotope fractionation of L. sibirica during the growing season is relative humidity during the growing season. The tree-ring δ13Ccorr of P. schrenkiana is significantly and negatively correlated with the mean temperature, mean minimum temperature, precipitation, and vapor pressure deficit from the end of the previous growing season and throughout the current growing season, especially in summer. However, it is significantly and positively correlated with relative humidity, indicating that the relationship between the climate factors and the tree-ring stable carbon isotope fractionation of P. schrenkiana is more complex. Further analysis showed that summer temperature and summer precipitation jointly controlled the tree-ring stable carbon isotope fractionation of P. schrenkiana at a high elevation. This research has important implications for our understanding of past and future climate change, as well as for the development of effective strategies to mitigate and adapt to these changes. This study also contributed to the development of a more in-depth understanding of the effects of climate change on tree growth in extremely arid environments and provided evidence to support effective forest management in arid regions.

TWO NEW MILLENNIUM-LONG TREE-RING OXYGEN ISOTOPE CHRONOLOGIES (2349–1009 BCE AND 1412–466 BCE) FROM JAPAN

ABSTRACTWe present two new millennium-long tree-ring oxygen isotope chronologies for central and northern Japan, based on 9693 annually resolved measurements of tree-ring oxygen isotopes from 39 unearthed samples consisting mainly of Japanese cedar (Cryptomeria japonica). These chronologies were developed through cross-dating of tree-ring widths and δ18O data from multiple samples covering the periods 2349–1009 BCE (1341 yr) and 1412–466 BCE (947 yr) for central and northern Japan, respectively. In combination with our published chronology for central Japan, the tree-ring δ18O dataset currently available covers the past 4354 yr (2349 BCE to 2005 CE), which represents the longest annually resolved tree-ring δ18O dataset for Asia. Furthermore, the high-resolution temporal record of 14C contents independently developed by Sakurai et al. (2020) was reproduced by our 14C measurements of earlywood and latewood in annual rings for the period 667–660 BCE.

Analysis on multi period activity and evolution of Yingxiu-Beichuan fault in Longmenshan area

As the boundary between the Yangtze Craton and the Qinghai-Tibet Plateau, the Longmenshan tectonic belt is known for its typical fault-slip systems and strong Cenozoic activities. Due to the complexity of the structure of the orogenic belt, the tectonic evolution and formation mechanism of the Longmenshan tectonic belt have been controversial. This paper essentially focuses on the geological isotopic chronology limitation of the fault activity of the Longmenshan Central Fault (Yingxiu-Beichuan Fault). The K-Ar dating of the illite in the fault gouge sample on the fault surface reveals that the direct age of the fault would be about 111 Ma. Combined with the previous age results, the following results are obtained: The Yingxiu-Beichuan fault was a multi-stage active fault in the Mesozoic, which was active in the Late Triassic (229–216 Ma), Early Jurassic (190–171 Ma) and the end of Early Cretaceous (130–110Ma). This paper analyzes the evolution of the central fault through regional geological evolution, seismic profile analysis and structural physical simulation experiment, and the following main results are obtained: Animaqing Paleo-Tethys Ocean on the northern margin of the Songpan Garze Block and the Jinshajiang Paleo Tethys Ocean in the southern margin were closed successively in the Middle and Late Triassic, Such a fact essentially occurred under the influence of differential uplift, that is, the pre-existing Yingxiu-Beichuan fault changed from a normal fault to a reverse fault in the Late Triassic, and then reactivated. Under the influence of the gravity slip mechanism, the Yingxiu-Beichuan fault was active until it ceased in the Early Jurassic. Since then, affected by the closure of the Middle Tethys Ocean, in the Early Cretaceous, the fault developed again, and branch faults developed in front of the fault. During the Himalayan period, due to the collision and ccocnnection of the Eurasian plate and the Indian plate, the fault was reactivated.

Tree-ring isotopes from the Swiss Alps reveal non-climatic fingerprints of cyclic insect population outbreaks over the past 700years.

Recent experiments have underlined the potential of δ2H in tree-ring cellulose as a physiological indicator of shifts in autotrophic versus heterotrophic processes (i.e., the use of fresh versus stored non-structural carbohydrates). However, the impact of these processes has not yet been quantified under natural conditions. Defoliator outbreaks disrupt tree functioning and carbon assimilation, stimulating remobilization, therefore providing a unique opportunity to improve our understanding of changes in δ2H. By exploring a 700-year tree-ring isotope chronology from Switzerland, we assessed the impact of 79 larch budmoth (LBM, Zeiraphera griseana [Hübner]) outbreaks on the growth of its host tree species, Larix decidua[Mill]. The LBM outbreaks significantly altered the tree-ring isotopic signature, creating a 2H-enrichment and an 18O- and 13C-depletion. Changes in tree physiological functioning in outbreak years are shown by the decoupling of δ2H and δ18O (O-H relationship), in contrast to the positive correlation in non-outbreak years. Across the centuries, the O-H relationship in outbreak years was not significantly affected by temperature, indicating that non-climatic physiological processes dominate over climate in determining δ2H. We conclude that the combination of these isotopic parameters can serve as a metric for assessing changes in physiological mechanisms over time.

Climate impacts on tree-ring stable isotopes across the Northern Hemispheric boreal zone

Boreal regions are changing rapidly with anthropogenic global warming. In order to assess risks and impacts of this process, it is crucial to put these observed changes into a long-term perspective. Summer air temperature variability can be well reconstructed from conifer tree rings. While the application of stable isotopes can potentially provide complementary climatic information over different seasons.In this study, we developed new triple stable isotope chronologies in tree-ring cellulose (δ13Ctrc, δ18Otrc, δ2Htrc) from a study site in Canada. Additionally, we performed regional aggregated analysis of available stable isotope chronologies from 6 conifers' tree species across high-latitudinal (HL) and - altitudinal (HA) as well as Siberian (SIB) transects of the Northern Hemispheric boreal zone.Our results show that summer air temperature still plays an important role in determining tree-ring isotope variability at 11 out of 24 sites for δ13Ctrc, 6 out of 18 sites for δ18Otrc and 1 out of 6 sites for δ2Htrc. Precipitation, relative humidity and vapor pressure deficit are significantly and consistently recorded in both δ13Ctrc and δ18Otrc along HL.Summer sunshine duration is captured by all isotopes, mainly for HL and HA transects, indicating an indirect link with an increase in air and leaf temperature. A mixed temperature-precipitation signal is preserved in δ13Ctrc and δ18Otrc along SIB transect. The δ2Htrc data obtained for HL-transect provide information not only about growing seasonal moisture and temperature, but also capture autumn, winter and spring sunshine duration signals. We conclude that a combination of triple stable isotopes in tree-ring studies can provide a comprehensive description of climate variability across the boreal forest zone and improve ecohydrological reconstructions.

The Relationship between Fluid Evolution and Hydrocarbon Accumulation and Metallization in the Nanpanjiang-Youjiang Basin: Evidence from Calcite Petrography and Fluid Inclusions

In the process of diagenesis and burial of sedimentary basins, basin fluid activities participate in the process of hydrocarbon accumulation and metal mineralization. Understanding the evolution of basin fluid is of great significance in revealing the related hydrocarbon accumulation and mineralization. Paleo-reservoirs are closely associated with Carlin-type gold deposits in the Nanpanjiang-Youjiang Basin, South China. Calcite, the fluid activity product, is closely related to bitumen and gold-bearing pyrite. By integrating petrographic, cathode luminescence, and fluid inclusion analysis, as well as the relevant chronological results of predecessors, this paper attempts to establish the relationship between fluid evolution, hydrocarbon accumulation, and gold mineralization. Two types of calcite (black/gray and white) developed in the Banqi-Yata-Laizishan area, the Nanpanjiang-Youjiang Basin. Black/gray calcite is symbiotic with bitumen and features dark red colors in cathode luminescence. Many hydrocarbon inclusions developed along with fluid inclusion analysis at low homogenization temperatures (65.7~173.1 °C). Combining the previously reported U-Pb ages (~250–230 Ma) of this kind of calcite with some geochemistry data on the associated reservoir and gold deposit, this calcite records the consecutive hydrocarbon accumulation and Carlin-type gold mineralization from the Late Permian to the Late Triassic periods controlled by Indosinian tectonic movement. The white calcite featuring bright red in cathodoluminescence is symbiotic with gold-bearing pyrite and realgar, and the associated fluid inclusions have high homogenization temperatures (128.2~299.9 °C). Combined with regional tectonic background and isotopic chronology (~140–106 Ma), it seems to record the early Cretaceous Carlin-type gold mineralization controlled by the subduction of the paleo-Pacific plate in the late Yanshanian period.

Inter-annual and intra-annual tree-ring oxygen isotope signals in response to monsoon rainfall in northwestern Thailand

We present a new teak ( Tectona grandis L.f.) tree-ring stable oxygen isotope (δ18OTR) chronology from Mae Tuen (MT) site, Tak province, northwestern Thailand at inter-annual (167-year, A.D.1850–2016) and intra-annual (A.D.2006–2016) timescales. The inter-annual δ18OTR chronology showed a significant negative correlation ( r = −0.678, p < 0.01) with the May–October amount of regional rainfall obtained from CRU TS4.03. We established a linear regression model that explained 46.0% of the actual rainfall variance and reconstructed monsoon season rainfall back to A.D.1850. The seasonal variations in moisture conditions were reflected in inter-annual δ18OTR variability. The rainfall amount and δ18O in precipitation (δ18Op) mainly controlled intra-annual variations in teak δ18OTR. These results show that the variation in Thai teak δ18OTR is dominated by rainfall, highlighting the strength of δ18OTR as a monsoon rainfall proxy.