geological time
Recently Published Documents


TOTAL DOCUMENTS

1021
(FIVE YEARS 262)

H-INDEX

62
(FIVE YEARS 9)

2022 ◽  
Author(s):  
Shinya Iwasaki ◽  
Lester Lembke-Jene ◽  
Kana Nagashima ◽  
Helge Arz ◽  
Naomi Harada ◽  
...  

Abstract Southern Ocean deep-water circulation plays an important role in the global carbon cycle. On geological time-scales, upwelling along the Chilean continental margin likely contributed to the deglacial atmospheric carbon dioxide rise, but little quantitative evidence exists of carbon storage. Here, we use a new X-ray Micro-Computer-Tomography method to assess foraminiferal test dissolution as proxy for paleo-carbonate ion concentrations ([CO32−]). Our subantarctic Southeast Pacific sediment core depth transect shows significant deep-water [CO32−] variations during the Last Glacial Maximum and Deglaciation (10 – 22 ka BP). We provide evidence for an increase in [CO32−] during the early deglacial period (15-19 ka BP), followed by a ca. 40 µmol kg−1 reduction in Lower Circumpolar Deepwater (CDW). This decreased Pacific to Atlantic export of low-carbon CDW contributed to significantly lowered carbon storage within the Southern Ocean, highlighting the importance of a dynamic Pacific–Southern Ocean deep-water reconfiguration for shaping late-glacial oceanic carbon storage, and subsequent deglacial oceanic-atmospheric CO2 transfer.


2022 ◽  
Vol 11 (1) ◽  
pp. 47
Author(s):  
Handong He ◽  
Yanrong Liu ◽  
Jing Cui ◽  
Di Hu

Knowing the GIS expression of geological phenomena is an important basis for the combination of geology and GIS. Regional geological structures include folds, faults, strata, rocks, and other typical geological phenomena and are the focus of geological GIS research. However, existing research on the GIS expression of regional geological structure focuses on the expression of the spatial and attribute characteristics of geological structures, and our knowledge of the expression of the semantic, relationship, and evolution processes of geological structures is not comprehensive. In this paper, a regional geological structure scene expression model with the semantic terms positional accuracy, geometric shape, relationship type, attribute type, and time-type attributes and operations is proposed. A regional geological structure scenario markup language (RGSSML) and a method for mapping it with graphics are designed to store and graphically express regional geological structure information. According to the geological time scale, a temporal reference coordinate system is defined to dynamically express the evolution of regional geological structures. Based on the dynamic division of the time dimension of regional geological structures, the expression method of “time dimension + space structure” for the regional geological structure evolution process is designed based on the temporal model. Finally, the feasibility and effectiveness of the regional geological structure scene expression method proposed in this paper is verified using the Ningzhen Mountain (Nanjing section) as an example. The research results show that the regional geological structure scene expression method designed in this paper has the following characteristics: (1) It can comprehensively express the spatial characteristics, attribute characteristics, semantics, relationships, and evolution processes of regional geological structures; (2) it can be used to realize formalized expression and unified storage of regional geological information; and (3) it can be used to realize dynamic expression of the regional geological structure evolution process. Moreover, it has significant advantages for the expression of regional geological structure semantics, relationships, and evolution processes. This study improves our knowledge of the GIS expression of regional geological structures and is expected to further promote the combination and development of geology and GIS.


Biology ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 98
Author(s):  
Shuaishuai Dong ◽  
Yanli Lei ◽  
Hongsheng Bi ◽  
Kuidong Xu ◽  
Tiegang Li ◽  
...  

Understanding the way in which a decline in ocean pH can affect calcareous organisms could enhance our ability to predict the impacts of the potential decline in seawater pH on marine ecosystems, and could help to reconstruct the paleoceanographic events over a geological time scale. Planktic foraminifera are among the most important biological proxies for these studies; however, the existing research on planktic foraminifera is almost exclusively based on their geochemical indices, without the inclusion of information on their biological development. Through a series of on-board experiments in the western tropical Pacific (134°33′54″ E, 12°32′47″ N), the present study showed that the symbiont-bearing calcifier Trilobatus sacculifer—a planktic foraminifer—responded rapidly to a decline in seawater pH, including losing symbionts, bleaching, etc. Several indices were established to quantify the relationships between these biological parameters and seawater pH, which could be used to reconstruct the paleoceanographic seawater pH. We further postulated that the loss of symbionts in planktic foraminifera acts as an adaptive response to the stress of low pH. Our results indicate that an ongoing decline in seawater pH may hinder the growth and calcification of planktic foraminifera by altering their biological processes. A reduction in carbonate deposition and predation could have profound effects on the carbon cycle and energy flow in the marine food web.


2022 ◽  
Author(s):  
Alexander Simpson ◽  
Stijn Glorie ◽  
Martin Hand ◽  
Carl Spandler ◽  
Sarah Gilbert ◽  
...  

Abstract. The ability to constrain the age of calcite formation is of great utility to the Earth Science community, due to the ubiquity of calcite across a wide spectrum of geological systems. Here, we present the first in-situ laser ablation inductively coupled tandem mass spectrometry (LA-ICP-MS/MS) Lu–Hf ages for calcite, demonstrating geologically meaningful ages for IOCG and skarn mineralisation, carbonatite intrusion and low grade metamorphism. The analysed samples range in age between ca. 0.9 Ga and ca. 2 Ga with uncertainties between 1.4 % and 0.5 % obtained from calcite with Lu concentrations as low as ca. 0.5 ppm. The Lu–Hf system in calcite appears to be able to preserve primary precipitation ages over a significant amount of geological time, although further research is required to constrain the closure temperature. The in-situ approach allows calcite to be rapidly dated while maintaining its petrogenetic context with mineralization and other associated mineral processes. Therefore, LA-ICP-MS/MS Lu–Hf dating of calcite can be used to resolve the timing of complex mineral paragenetic sequences that are a feature of many ancient rock systems.


2021 ◽  
Vol 30 (4) ◽  
pp. 741-753
Author(s):  
Olena A. Sirenko ◽  
Olena A. Shevchuk

The article presents an analysis of a large array of results of palynological studies of Mesozoic and Cenozoic sediments of Ukraine and adjacent regions of Belarus and Russia. Numerous literature data on the palynological characteristics of Meso-Cenozoic sediments and the materials of the authors are summarized according to the results of spore-pollen analysis of Mesozoic and Cenozoic sediments within the main tectonic structures of Ukraine. It has been established that the genus Pinus (Pinaceae) is an integral part of the Meso-Cenozoic flora of Ukraine. Although, the participation in the flora and vegetation of the genus Pinus and its species diversity in different periods of geological time were different. Despite the long history and significant achievements of palynological research of Meso-Cenozoic sediments of Ukraine, no attention has been paid to the historical aspect of Pinus development in the Meso-Cenozoic flora. This work is presented as the first stem to fill this gap. The genus Pinus has a large stratigraphic range, but its species diversity and quantitative changes in the composition of Mesozoic and Cenozoic flora of different ages are markedly different. The analysis of these changes made it possible to trace the emergence and main levels at which the species composition was renewed and the role of Pinus in flora increased during the Mesozoic and Cenozoic. According to the results of the research, 5 levels of increasing the participation of the genus Pinus and changes in its species affiliation in the Mesozoic flora were established: Aalenian period of the Middle Jurassic (appearance of the first representatives of Pinus); Oxfordian time of the Late Jurassic; Valanginian – Early Barremian times of the Early Cretaceous; Albian time of the Early Cretaceous; Late Campanian time of the Late Cretaceous. 5 levels of increasing the role of Pinus and its species diversity for the flora and vegetation of the Cenozoic were also established: Oligocene time of the Paleogene, Konkian-early Sarmatian time of the Middle Miocene; early Pontian (Ivankov) time of the Late Miocene; early Kimmerian time (early Sevastopol) of the Early Pliocene and Martonosha time of the Early Neopleistocene. Certain levels have been traced for the similar age of Cenozoic flora of Belarus and Russia.


2021 ◽  
Author(s):  
Adrian Broz ◽  
Joanna Clark ◽  
Brad Sutter ◽  
Doug Ming ◽  
Valerie Tu ◽  
...  

Ancient (4.1-3.7-billion-year-old) layered sedimentary rocks on Mars are rich in clay minerals which formed from aqueous alteration of the Martian surface. Many of these sedimentary rocks appear to be composed of vertical sequences of Fe/Mg clay minerals overlain by Al clay minerals that resemble paleosols (ancient, buried soils) from Earth. The types and properties of minerals in paleosols can be used to constrain the environmental conditions during formation to better understand weathering and diagenesis on Mars. This work examines the mineralogy and diagenetic alteration of volcaniclastic paleosols from the Eocene-Oligocene (43-28 Ma) Clarno and John Day Formations in eastern Oregon as a Mars-analog site. Here, paleosols rich in Al phyllosilicates and amorphous colloids overlie paleosols with Fe/Mg smectites that altogether span a sequence of ~500 individual profiles across hundreds of meters of vertical stratigraphy. Samples collected from three of these paleosol profiles were analyzed with visible/near-infrared (VNIR) spectroscopy, X-ray diffraction (XRD), and evolved gas analysis (EGA) configured to operate like the SAM-EGA instrument onboard Curiosity Mars Rover. Strongly crystalline Al/Fe dioctahedral phyllosilicates (montmorillonite and nontronite) were the major phases identified in all samples with all methods. Minor phases included the zeolite mineral clinoptilolite, as well as andesine, cristobalite, opal-CT and gypsum. Evolved H2O was detected in all samples and was consistent with adsorbed water and the dehydroxylation of a dioctahedral phyllosilicate, and differences in H2O evolutions between montmorillonite and nontronite were readily observable. Detections of hematite and zeolites suggested paleosols were affected by burial reddening and zeolitization, but absence of illite and chlorite suggest that potash metasomatism and other, more severe diagenetic alterations had not occurred. The high clay mineral content of the observed paleosols (up to 95 wt. %) may have minimized diagenetic alteration over geological time scales. Martian paleosols rich in Al and Fe smectites may have also resisted severe diagenetic alteration, which is favorable for future in-situ examination. Results from this work can help distinguish paleosols and weathering profiles from other types of sedimentary rocks in the geological record of Mars.


2021 ◽  
Author(s):  
Maoshan Chen ◽  
Zhonghong Wan ◽  
Changhong Wang ◽  
Jingyan Liu ◽  
Zhaoqin Chen

Summary Due to the rapid increase in the amount of seismic volumes, the traditional seismic interpretation mode based on manual structure interpretation and single-horizon automatic tracking has encountered many challenges. The seismic interpretation of large or super-large 3-D seismic surveys is facing serious accuracy and efficiency bottlenecks. Aiming to the goal of improving the accuracy and efficiency of seismic interpretation, we propose a dynamic seismic waveform matching technology based on the sparse dynamic time warping algorithm under the guidance of the relative geological time volume theory, and realize multi-horizon simultaneous tracking based on the technology. Has been verified by a model and a real seismic volume, it can realize simultaneous horizon automatic tracking, full spatial tracking and high-density tracking, and can significantly improve the accuracy and efficiency of structure interpretation.


2021 ◽  
pp. M58-2021-12
Author(s):  
Michael A. Summerfield

AbstractThe plate tectonics revolution was the most significant advance in our understanding of the Earth in the 20th century, but initially it had little impact on the discipline of geomorphology. Topography and landscape development were not considered to be important phenomena that deserved attention from the broader earth-science community in the context of the new model of global tectonics. This situation began to change from the 1980s as various technical innovations enabled landscape evolution to be modelled numerically at the regional to sub-continental scales relevant to plate tectonics, and rates of denudation to be quantified over geological time scales. These developments prompted interest amongst earth scientists from fields such as geophysics, geochemistry and geochronology in understanding the evolution of topography, the role of denudation in influencing patterns of crustal deformation, and the interactions between tectonics and surface processes. This trend was well established by the end of the century, and has become even more significant up to the present. In this chapter I review these developments and illustrate how plate tectonics has been related to landscape development, especially in the context of collisional orogens and passive continental margins. I also demonstrate how technical innovations have been pivotal to the expanding interest in macroscale landscape development in the era of plate tectonics, and to the significant enhancement of the status of the discipline of geomorphology in the earth sciences over recent decades.


2021 ◽  
Author(s):  
Igor S. Pessi ◽  
Aino Rutanen ◽  
Jenni Hultman

AbstractAmmonia-oxidizing archaea (AOA) are key players in the nitrogen cycle. Here, we report four novel metagenome-assembled genomes (MAGs) assigned to the genus “UBA10452”, an uncultured lineage of putative AOA in the family Nitrososphaeraceae. Analysis of other eight previously reported MAGs and publicly available amplicon sequencing data revealed that the UBA10452 lineage is predominantly found in acidic polar and alpine soils. We propose a novel Candidatus genus, Ca. Nitrosopolaris, with four species representing clear biogeographical/habitat clusters. In addition to the presence of genes involved in cold adaptation, we hypothesize that the distribution of Ca. Nitrosopolaris across the cold biosphere might also be due to the combination of a polar origin and limited dispersal capabilities throughout geological time.


Sign in / Sign up

Export Citation Format

Share Document