Hasil untuk "Geology"

M. K. Hubbert

J. Kulp, J. C. Cobb, L. E. Long et al.

W. Dow

D. Rosen

M. Talwani, O. Eldholm

E. Roedder, R. Bodnar

W. Schlager

R. Goodman

Rushdi Said

Marco Luppichini, Stefano Natali, Andrea Columbu et al.

Abstract Precipitation variability in the Mediterranean Basin has traditionally been attributed to large-scale Atlantic climate modes, particularly the North Atlantic Oscillation (NAO). However, over key regions such as the Italian Peninsula, NAO-based interpretations often fall short in explaining observed hydroclimatic patterns. In this study, we combine deep learning reconstruction of historical precipitation records from 1950 to 2020 with the analysis of atmospheric teleconnection indices and air mass back-trajectory modelling. Using a dataset of more than eleven thousand rain gauge time series, we developed neural network models to produce a continuous and high-resolution precipitation dataset for Italy. Our results demonstrate that Mediterranean teleconnections, especially the Mediterranean Oscillation Index (MOI) and the Western Mediterranean Oscillation (WeMO), exert a stronger and more consistent influence on precipitation compared to the NAO. Trajectory analysis using the HYSPLIT model reveals that the Western Mediterranean is the dominant moisture source for central and northern Italy, while the Ionian and Eastern Mediterranean regions become increasingly important in the southern part of the country. These findings underscore the central role of Mediterranean cyclogenesis in shaping regional precipitation dynamics and call for a reassessment of climate interpretation frameworks that have traditionally focused on Atlantic influences alone.

Itohan-Osa Abu, Chibuike Chiedozie Ibebuchi

Hydrological extremes, particularly floods, are becoming prevalent in parts of Nigeria. During the 2022 rainy season, Nigeria experienced a devastating riverine flood with severe societal impacts. However, the principal factors contributing to riverine flooding in Nigeria remain debatable, necessitating data-driven and policy-relevant studies to quantify the primary causes of riverine floods in Nigeria. In this study, we applied remote sensing techniques and climate data to characterize the 2022 flood event in Nigeria by quantifying the flooded areas, the number of people affected per state, and riverine flood risk assessment. We investigated rainfall and soil moisture anomalies during the flood event and inferred the contribution of the opening of the Lagdo Dam, in Cameroon, to the severity of the flood event. Our results show that large parts of Cameroon and northern Nigeria experienced above-average rainfall during the 2022 rainy season, contributing to soil saturation. About 50,000 ha of land were flooded in Nigeria between July and August; however, following the opening of the Lagdo Dam in September, the flood extent spiked to 200,000 ha (i.e., about 300% increase), suggesting that excess water from the Lagdo Dam, coupled with inadequate drainage infrastructure, amplified the flood extent in Nigeria. Flooded areas were more extensive in northern Nigeria than in southern regions; however, due to denser settlements in flood-prone areas, Anambra State in southeastern Nigeria was the most affected in terms of people impacted. Therefore, besides rainfall changes and inadequate drainage infrastructures leading to the inundation of the major rivers in Nigeria and their tributaries, we also ranked poor town planning against the population density per square meter as a critical factor that amplifies the societal impacts of flooding in Nigeria. Finally, based on the 2022 conditions and the available pre-flood population data, an estimated number of 105,000 people are at critical risk of riverine flooding in Nigeria.

S. Schumm

C. Baied, D. Piperno

Reddy Setyawan, Yoga Aribowo, Anis Kurniasih et al.

The structure of Exia is composed of Miocene built-up carbonates formed by shear faults. The buildup carbonate feature in the Exia prospect can be seen from the high elevation surrounded by lows with an NNE-SSW and NE-SW trending. The MA-1, SE-1, MI-1 wells are several wells in the Tiaka and Senoro Fields which are proven to have large gas reserves. Tiaka Field is located to the west of the Exia Well, while Senoro Field is to the northeast. The study used primary data from the Exia-1 well in the form of cutting samples. The wet and dry cutting samples were further processed into thin section. This thin section is then carried out for petrographic, XRD, and SEM analysis. Tomori Formation starts from the deeper environment FZ1 upwards to the shallower FZ5 –FZ6 (reef) with open marine and restricted areas. The allochem that composes the limestone at The Matindok Formation consists of red algae fragments and benthic forams which indicate the facies zone of formation in FZ 4 (slope). In the upper Mantawa Formation, it is still quite clear the presence of large forams indicating a reef association environment (FZ5-FZ6), but the presence of a large number of planktonic forams indicates a deeper depositional environment / slope, so it is possible that large forams were transported from a shallower environment. The Kintom Formation have rock provenance ranging from continental blocks in the interior of the craton to a recycled orogeny section of recycled quartz zone.

A. Hope Jahren, Brian A. Schubert

Abstract Widespread drought driven by global warming is predicted across the 21st century, just as CO2 level is projected to as much as double over the same time period. However, the potential interplay between increasing CO2 and decreasing soil moisture on plant function is uncertain, as previous works have not successfully separated and quantified these two competing effects. Here we evaluated the interaction between soil moisture and CO2 using stable carbon isotope measurements of Arabidopsis grown under the simultaneous modulation of an exhaustive range of both variables. Results showed that both increasing soil water content and increasing CO2 increased isotopic discrimination, and that the soil moisture effect was not influenced by the CO2 level and vice versa. Our data confirm that changes in the carbon isotope record of terrestrial organic matter preserved within the geologic record are best interpreted as deriving from changes in atmospheric CO2.

WU Zhonghai

Objective  The Qinghai-Tibet Plateau is one of the most seismically active regions along the Mediterranean-Himalayan seismic belt. Understanding the earthquake-controlling effect of the active tectonic system in this region is crucial for analyzing regional strong earthquake hazards.  Methods  We analyzed earthquake activity with MW≥6.0 since 1990 and their tectonic mechanism around the Tibetan Plateau, focusing on the continental collision-extrusion tectonic system.  Results  The results show that the system plays a significant role in governing regional strong earthquake activity. Specifically, MW≥6.5 earthquakes primarily occur along the main boundary fault zone of this tectonic system, exhibiting a relatively regular spatio-temporal migration process. Moreover, the multi-layered extrusion-rotation active tectonic system in the eastern Tibetan Plateau constitutes the primary earthquake-controlling structure of the strong earthquake process since 1990, followed by the thrust faults of the Himalayan foreland. Therefore, the extrusion tectonic system of the Qinghai-Tibet Plateau should be the focus for the trend analysis of the strong earthquake activity in the future, especially the most active secondary extrusion tectonic units such as the Bayan Har block. Comparative analysis of strong earthquake activities in and around the Anatolian plate reveals similar continental collision-extrusion tectonic systems and earthquake-controlling effects in this area, indicating that this tectonic system is a typical earthquake-controlling structure in the intracontinental orogenic belt.  Conclusion  Further comprehensive analysis suggests that the active tectonic system can significantly control regional strong earthquake activity. Firstly, most of the strong earthquake events occur in the main boundary fault zone of the fault block in the tectonic system. Secondly, the strong earthquake events along different structural zones in the tectonic system often have linkage effects or mutual triggering relationships, and the complex or particular structural sites are often where double earthquakes or earthquake swarm activities easily occur. Thirdly, when a certain structural unit or tectonic zone in the tectonic system is in an active stage, strong earthquake clustering phenomena occur.  Significance  A thorough understanding of the coordinated deformation relationships between major active faults in the tectonic system, the segmented rupture behavior of strong earthquake activity in active fault zones, and the characteristics of "long period, quasi-periodicity and clustering" of strong earthquake recurrence in situ on active faults will assist in more accurately assessing the future seismic hazard of active fault zones when analyzing the future trend of strong earthquake activity based on the active tectonic system.

C. Koltermann, S. Gorelick

Tao ZENG, Shaocong JI, Wenqian XIA et al.

The carbonate karst reservoir of Maokou formation is developed in the Yuanba area, northern Sichuan Basin. However, it is difficult to predict this set of reservoir because of its strong heterogeneity. Therefore, for the guidance of future oil and gas exploration and development, it is necessary for us to further restore karst paleo-geomorphology and paleo-water system so as to master the law of reservoir distribution. In order to better depict the micro karst landform, the ''the trend surface of residual thickness and impression residual" are combined to restore the ancient landform. According to the characteristics of karst paleo-geomorphology on the top of Maokou Formation in Yuanba area and the thickness from the top of Maokou formation to the top of its first section in Yuanba area, an index system for the classification of karst paleo-geomorphology types is established. Based on the thickness mentioned above, the paleogeographic environment and paleo-hydrodynamic conditions, the study area is divided into four second-tier geomorphic units—karst platform, gentle karst slope, karst plain and karst basin. Then, in terms of modern karst classification, a third-tier geomorphic units are subdivided into six types—micro hill depression, hill-cluster depression, micro hill trough, cluster-peak depression, hill-cluster ridge valley and monadnock plain, according to the micro geomorphic combination form of karst paleo-geomorphology on the top of Maokou Formation in Yuanba area. Based on the characteristics of paleo-topography as well as the plane distribution and mutual configuration relationship of the six third-tier geomorphic units, the surface water system of the paleo-karst surface at the top of Maokou formation in Yuanba and its adjacent areas is constructed. In general, controlled by the ancient topography, the surface runoff is mainly the scattered runoff from the karst platform to both sides. The ancient water system is not well developed with no centralized runoff system, and only small gullies and karst lakes are locally developed. On the whole, the ancient karst landform on the top of Maokou formation in the study area belongs to the initial stage of the formation and evolution of karst landform. The relative elevation difference of the regional terrain which is slightly undulating is generally less than 120 m. The relative elevation difference of hills (peaks) and depressions is generally less than 10-30 m, which belongs to the initial stage of tectonic uplift and denudation and is characterized by coastal (island) karst landform, and the surface water system is not fully formed. The karstification time of the study area is relatively short, belonging to the initial stage of epigenetically exposed karst which is characterized by the joint karstification of atmospheric fresh water and seawater. The karstification mode is mainly the leaching and infiltration of atmospheric fresh water, which is difficult to form concentrated lateral runoff. Karstification mainly occurs in the shallow part, and karst is dominated by dissolution holes. Large-scale karst fractures and caves have not been formed. There are great differences in karst development in different geomorphic locations, among which the karst platform belongs to the groundwater recharge area; the atmospheric precipitation is mainly vertical infiltration; and the lateral runoff of groundwater is slow. The karst plain belongs to groundwater runoff and discharge area, where groundwater runoff is slow, and the intensity of karstification is relatively weak. The karst basin belongs to groundwater drainage area with long water-rock interaction cycle and weak karstification intensity. The gentle karst slope belongs to groundwater runoff area with the strongest hydrodynamic force and the most developed holes, which is suitable for the future reservoir exploration.

J. Ma, S. Olin, P. Anthoni et al.

<p>Biological nitrogen fixation (BNF) from grain legumes is of significant importance in global agricultural ecosystems. Crops with BNF capability are expected to support the need to increase food production while reducing nitrogen (N) fertilizer input for agricultural sustainability, but quantification of N fixing rates and BNF crop yields remains inadequate on a global scale. Here we incorporate two legume crops (soybean and faba bean) with BNF into a dynamic vegetation model LPJ-GUESS (Lund–Potsdam–Jena General Ecosystem Simulator). The performance of this new implementation is evaluated against observations from a range of water and N management trials. LPJ-GUESS generally captures the observed response to these management practices for legume biomass production, soil N uptake, and N fixation, despite some deviations from observations in some cases. Globally, simulated BNF is dominated by soil moisture and temperature, as well as N fertilizer addition. Annual inputs through BNF are modeled to be <span class="inline-formula">11.6±2.2</span> Tg N for soybean and <span class="inline-formula">5.6±1.0</span> Tg N for all pulses, with a total fixation of <span class="inline-formula">17.2±2.9</span> Tg N yr<span class="inline-formula">⁻¹</span> for all grain legumes during the period 1981–2016 on a global scale. Our estimates show good agreement with some previous statistical estimates but are relatively high compared to some estimates for pulses. This study highlights the importance of accounting for legume N fixation process when modeling C–N interactions in agricultural ecosystems, particularly when it comes to accounting for the combined effects of climate and land-use change on the global terrestrial N cycle.</p>

I. Kühn, R. Brandl, S. Klotz