Knowledge of Holocene hydro-climatic conditions in northern China from high temporal resolution stalagmites collected from Lianghua Cave

Our understanding of hydro-climatic dynamics in the East Asian monsoon region during the Holocene was obstructed by very few absolutely dated and high temporally resolved proxy records in northern China. Here we present duplicated carbonate δ18O records of six stalagmites with sub-decadal to multi-decadal temporal resolutions from Lianhua cave to reveal a detailed transition of the East Asian Summer Monsoon (EASM) intensity in northern China from 11.5 thousand years ago (hereafter, ka BP, before 1950 AD). Our composite records show that solar forcing dominated hydro-climatic changes, including an intensified monsoon at the Holocene Optimum from the end of Younger Dryas to 6.5 ka BP, and a subsequent multi-millennial weakening of monsoon intensity, that agree with cave records in central and southern China. However, the EASM has retreated southwards more rapidly than the Indian summer monsoon after ∼6.5 ka BP, resulting in some rapid onset of dry conditions occurring at 4.0 ka BP in northern China, which is ∼2000 years earlier than in central and southern China. This asynchrony may be related to the different regional responses among the coupling of the EASM, Indian summer monsoon, the solar forcing, and the differences in thermal forcing due to complex geographical configurations. In addition, a relative enrichment of 1h in our δ18O data of Lianhua record from 9.5 to 8.1 ka BP shows that the Holocene Optimum was punctuated by a millennial-long weak monsoon interval, which is not registered among previous cave records in central and southern China. The freshwater-induced cold climate conditions in the North Atlantic region could create stronger East Asian winter monsoon and induce a weakened EASM and a southward shift of precipitation band in northern China. Therefore, it shall not be surprised that there are strong heterogeneities among regional hydro-climatic conditions across monsoonal China in the Holocene, given the complex interplay between external and internal forcing mechanisms over the entire Holocene

Asian monsoon dynamics at Dansgaard/Oeschger events 14-8 and Heinrich events 5-4 in northern China

A precisely 230Th-dated stalagmite oxygen isotope (δ18O) record from Dragon Cave,Shanxi Province, northern China, is proposed to reconstruct the millennial-scale changes of the East Asian Summer monsoon (EASM) during the period 53.2-1.3 ka BP (before 1950 AD). Our record shows significant millennial-scale oscillations that match in timing, characteristic, and duration with the Dansgaard/Oeschger (DO)30 events 14-8 and the Heinrich events 5, 4, 2, and 1 (hereafter H5, H4, H2 and H1) in high-latitude regions of the Northern Hemisphere. Especially, the H5 event is well constrained from 48.1 to 46.9 ka BP with ten 230Th dates. Our chronology supports the NGRIP GICC05 timescale from 50 to 38 ka BP. A comprehensive comparison of the Chinese speleothem records from different regions along a north-south transect shows a unique trend towards more negative δ 18O values from 48.0 to 38.0 ka BP, suggesting that an intensified Asian summer monsoon (ASM) across the whole monsoonal China during the interval. We speculate that the joint effect, from both the cooling of the Southern Hemisphere and the enhanced land-sea temperature contrast due to the rising summer insolation, is capable to regulate the low-latitude large-scale atmospheric circulation patterns and exert significant influences on the long-term ASM variations during the middle of Marine Isotope Stage 3

Estimation of an upper limit on prehistoric peak ground acceleration using the parameters of intact stalagmites and the mechanical properties of broken stalagmites in Domica Cave, Slovakia

Suitably shaped (tall, slim and more or less cylindriform), vulnerable, intact stalagmites (STM) in Domica cave have been examined. Some of these STMs are suitable to estimate the upper limit for horizontal peak ground acceleration generated by paleoearthquake. This research is the continuation of our previous examination of STMs in Baradla cave, north - east Hungary. The density, the Young’s modulus and the tensile failure stress of broken STM samples have been measured in mechanical laboratory, whereas the natural frequency and the heights and diameters of intact STMs were determined by in situ observation. The value of horizontal ground acceleration resulting in failure and the theoretical natural frequency of STM were assessed by theoretical calculations. The age of the samples taken from the STM(2.26m) standing in show part of Domica cave has been determined by Multi Collector – Inductively Coupled Plasma Mass Spectrometry analysis (MC-ICPMS). The a g value (the upper limit for horizontal peak ground acceleration ) need ed to break STM(5m) in Čertova diera (Ördög-lik) hall coming from theoretical calculation is almost the same (~ 0.059g) as - in case of STM(5.1m) in Olimposz hall (~0.055g) of Baradla cave. According to our measurements and theoretical calculations, in the last 2-5 kyears the geological structures close to Baradla and Domica caves have not generated paleoearthquakes, which would have produced horizontal ground acceleration larger than 0.061g. This value can be reached even in moderate size earthquakes. Our result has to be taken into account when calculating the seismic potential of faults near to Domica cave (e.g. Darnó,Plešivec (Pelsőc) and Rožňava (Rozsnyó) lines

Persistent termini of 2004- and 2005-like ruptures of the Sunda megathrust

To gain insight into the longevity of subduction zone segmentation, we use coral microatolls to examine an 1100-year record of large earthquakes across the boundary of the great 2004 and 2005 Sunda megathrust ruptures. Simeulue, a 100-km-long island off the west coast of northern Sumatra, Indonesia, straddles this boundary: northern Simeulue was uplifted in the 2004 earthquake, whereas southern Simeulue rose in 2005. Northern Simeulue corals reveal that predecessors of the 2004 earthquake occurred in the 10th century AD, in AD 1394 ± 2, and in AD 1450 ± 3. Corals from southern Simeulue indicate that none of the major uplifts inferred on northern Simeulue in the past 1100 years extended to southern Simeulue. The two largest uplifts recognized at a south-central Simeulue site—around AD 1422 and in 2005—involved little or no uplift of northern Simeulue. The distribution of uplift and strong shaking during a historical earthquake in 1861 suggests the 1861 rupture area was also restricted to south of central Simeulue, as in 2005. The strikingly different histories of the two adjacent patches demonstrate that this boundary has persisted as an impediment to rupture through at least seven earthquakes in the past 1100 years. This implies that the rupture lengths, and hence sizes, of at least some future great earthquakes and tsunamis can be forecast. These microatolls also provide insight into megathrust behavior between earthquakes, revealing sudden and substantial changes in interseismic strain accumulation rates

Radiocarbon dating of deep-sea corals

Deep-sea corals are a promising new archive of paleoclimate. Coupled radiocarbon and U-series dates allow ^(14)C to be used as a tracer of ocean circulation rate in the same manner as it is used in the modern ocean. Diagnetic alteration of coral skeletons on the seafloor requires a thorough cleaning of contaminating phases of carbon. In addition, 10% of the coral must be chemically leached prior to dissolution to remove adsorbed modern CO_2. A survey of modern samples from the full Δ^(14)C gradient in the deep ocean demonstrates that the coralline CaCO_3 records the radiocarbon value of the dissolved inorganic carbon

Influence Factor of Tertiary Students’ Employability Awareness Adjust Industry 4.0

This study aims to analyze the correlation (N=621) among tertiary students’ career planning, e-recruiting adoption acceptance, and employability awareness in Taiwan. Tertiary students’ perceived career planning includes four factors, namely, self-appraisal, job expectancy, goal selection, and problem solving. E-recruiting adoption acceptance includes four factors, namely, playfulness, ease of use, effectiveness, and usefulness. Employability awareness includes four factors, namely, personal adaptability , employability ambition, career identity, and labour market. Participants responded to a 5-point Likert-type scale for each factor. Analysis was conducted using the structural equation modeling (SEM), and a good model fit was found for both the measurement and structural models. Research findings demonstrate that tertiary students’ career planning significantly and directly influences employability awareness. Career planning significantly and indirectly influences employability awareness by e-recruiting adoption acceptance. Tertiary students’ career planning and e-recruiting adoption acceptance fit the influence model and empirical data of employability awareness. Implications of this study, including the value of student self-assessment of their skills and utility of the e-recruiting to underpin personal career development planning and inform graduate recruitment processes, are discussed and recommendations made

Early Holocene monsoon instability and climatic optimum recorded by Chinese stalagmites

The timing and duration of the Holocene East Asian summer monsoon (EASM) maximum and the interpretation of Chinese stalagmite δ18O records have long been disputed. Notably, interpretations of Holocene EASM variations are frequently based on a single record or study area and are often contradictory. In this study, we conducted stable isotope analyses of four Holocene stalagmites from Chongqing, southwest China. The results reveal differences in the timing of the Holocene EASM maximum and to try to resolve the inconsistency we analyzed and statistically integrated a total of 16 Holocene stalagmite records from 14 caves in the EASM region. The resulting synthesized Holocene stalagmite δ18O (δ18Osyn) record is in agreement with other EASM records and confirms that stalagmite δ18O records are a valid indicator of EASM intensity, rather of local precipitation amount. The δ18Osyn record shows that the EASM intensified rapidly from the onset of the early Holocene; notably, however, there were distinct EASM oscillations in the early Holocene, consisting of three abrupt millennial-scale events. This indicates that, contrary to several previous interpretations, the early Holocene EASM was unstable. Subsequently, during 8–6 kyr BP, the EASM was relatively stable and strong, with the strongest monsoon occurring during 8–7 kyr BP. This evidence of a stable and strong mid-Holocene EASM in eastern China is in accord with the classical view of a mid-Holocene Optimum in China

Measurements of Natural Carbonate Rare Earth Elements in Femtogram Quantities by Inductive Coupled Plasma Sector Field Mass Spectrometry

A rapid and precise standard-bracketing method has been developed for measuring femtogram quantity rare earth element (REE) levels in natural carbonate samples by inductively coupled plasma sector field mass spectrometry that does not require chemical separation steps. A desolvation nebulization system was used to effectively reduce polyatomic interference and enhance sensitivity. REE/Ca ratios are calculated directly from the intensities of the ion beams of 46Ca, 139La, 140Ce, 141Pr, 146Nd, 147Sm, 153Eu, 160Gd, 159Tb, 163Dy, 165Ho, 166Er, 169Tm, 172Yb, and 175Lu using external matrix-matched synthetic standards to correct for instrumental ratio drifting and mass discrimination. A routine measurement time of 3 min is typical for one sample containing 20-40 ppm Ca. Replicate measurements made on natural coral and foraminiferal samples with REE/Ca ratios of 2-242 nmol/mol show that external precisions of 1.9-6.5% (2 RSD) can be achieved with only 10-1000 fg of REEs in 10-20 μg of carbonate. We show that different sources for monthly resolved coral ultratrace REE variability can be distinguished using this method. For natural slow growth-rate carbonate materials, such as sclerosponges, tufa, and speleothems, the high sample throughput, high precision, and high temporal resolution REE records that can be produced with this procedure have the potential to provide valuable time-series records to advance our understanding of paleoclimatic and paleoenvironmental dynamics on different time scales

The multidisciplinary approaches on facies developments and depositional systems of the Bahcecik travertines, Gumushane, NE-Turkey

The Bahcecik travertines, located in Gumushane (NE-Turkey) have been investigated for the first time using a multidisciplinary approach, which included sedimentological (lithofacies, depositional system), petrographic, radiometric Th-230 dating, geochemical analysis (stable isotopes), palynomorphs and geophysics (GPR). A carbonate build-up, 12 m thick, was formed with some interruptions, through the middle Pleistocene period. For this study, two travertine sections (F and D) were extensively used to figure out palaeoenvironmental and palaeoclimatic proxies. The main precipitation cycles, separated by palaeosol levels, have been described and interpreted from a sedimentological perspective. The carbonate deposits consist of shrubs, crystalline crust, reed, laminated (micritic), pisoids, oncoids, calcite thin rafts and coated gas bubbles, lithoclasts, and palaeosol levels. The sedimentological fieldwork and petrographic analysis show that the Bahcecik travertines formed in depression depositional and slope depositional systems. Moreover, the first Th-230 ages, stable isotopic results and palynofloral data in this study, prove that the Bahcecik travertines might have been affected by climatic and tectonic interruptions. According to dating results, the travertine occurrences began to precipitate during the 353 ka and continued into the 263 ka. Based on the palynological data, an abundance of herbaceous plants species was recorded in the warming period of climate. The thickness ranges from 2 to 12 m of the Bahcecik travertines. This precise thickness and also the presence of two different travertine formations, separated by a palaeosol erosional surface, were recorded by the ground penetrating radar (GPR) geophysical method.Science Vanguard Research Program of the Ministry of Science and Technology (MOST), Taiwan, ROC 109-2123-M-002-001Higher Education Sprout Project of the Ministry of Education, Taiwan, ROC 109L901001National Taiwan University 110L890