The geotechnical ground investigation involves several testing techniques. Within such techniques, the Piezocone Penetration Test with seismic wave measurements (SCPTu) is one of the most popular. ...This test is widely used for in situ soil characterisation given its continuous measurements and repeatability. The interpretation of such test results has a strong theoretical background, namely allowing the identification the soil profile based on correlation of mechanical properties. In turn, the application of multivariate statistical methods allows identifying the soil stratigraphy by data association. This paper proposes a multivariate statistical approach, based on cluster analysis, for defining stratigraphic interfaces from SCPTu measurements. Using an extensive database from the Lower Tagus Valley region (near Lisbon, Portugal), this novel approach combines the four SCPTu parameters and recognises the association between the measurements. A comparison between statistical results against the profiles of soil behaviour index validates the efficiency of the approach, indicating a good agreement between data associations with the soil behaviour index profiles. The findings showed that the statistical procedure proposed in this study leads to reliable results for identifying soils with similar soil behaviour type.
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•Clustering of standardised raw SCPTu data for identifying soil stratigraphy.•Approach validation by comparing soil behaviour index profiles.•Detailed procedure for application in other geotechnical test sites.•Automatic statistical programming developed in RStudio, an open-source environment.
Submarine canyons serve as important sediment transport conduits from littoral zones to the deep sea, with strong impacts on the sedimentation patterns in marginal areas of the ocean. Moreover, such ...canyons can be major geohazards for submarine infrastructure, warranting a good understanding of their past and current behavior.
Here, we present a study of the geological history and the recent activity of the Nahariya submarine canyon, the longest of a system of ∼15 small blind canyons located in the eastern Mediterranean Sea, offshore Israel. Two piston cores retrieved from the middle and outlet of the canyon, at 650 m and 915 m water depth, respectively, were the focus of a multi-proxy study aiming to characterize sediment transport and deposition along the canyon during the Last Glacial and up to the present.
Both cores reveal a sequence of homogenous sediment of late last glacial age, which are capped by an unconformity overlying by fine laminated sediment dated to the last ∼200 years. Thus, the deglacial and most of the Holocene intervals are absent from the record. Evidence for down canyon sediment transport are abundant and include a 70 cm interval of mud clasts with disordered glacial ages that appears immediately below the hiatus, as well as broken calcareous shells of dead benthic foraminiferal species of shallow marine habitats, which are abundant throughout both cores. Similarly, shelf-derived living benthic foraminiferal species were found in the core-tops, indicating that active sediment transport persists along this canyon today.
We conclude that the history of Nahariya submarine canyon includes a period of sediment accumulation that lasted until the last deglaciation. Thereafter, the canyon was dominated by an erosive regime that persisted throughout the Holocene. Sediment accumulation resumed ∼200 years ago. We suggest that the recent resumption of sediment-accumulation is a result of anthropogenic amplification of on-land soil erosion accompanied by a wet period that persisted in the region and enhanced land to sea sediment transport.
•The geological history of a blind submarine canyon of E. Mediterranean is studied.•In-canyon last glacial sediment accumulation and Holocene erosion are observed.•Resumption of sediment accumulation occurred ca. 200 years ago.•This resumption reflects anthropogenic on-land soil erosion and shift to wet climate.•Shelf origin sediment is transported to deep canyon during glacial period and recent.
Morphometric analyses are based on multiparametric data sets that describe quantitatively the shapes of objects. The stochastic nature of fracture formation processes that break up magma during ...explosive eruptions yields mixtures of particles that have highly varied shapes. In volcanology, morphometric analysis is applied to these mixtures of particles with diverse shapes for two purposes: (1) to fingerprint tephra from individual eruptions and use the fingerprints to distinguish among tephra layers and determine their extents and (2) to reconstruct eruption processes, by linking particles formed by known fragmentation processes in experiments with particles from natural pyroclastic deposits. Here, we review the most commonly adopted statistical techniques for morphometric analysis of pyroclasts. We provide sets of objects with different shapes, along with their morphometric data, in order to demonstrate and illustrate the methods. They can be used not only for addressing the processes of fragmentation during explosive eruptions, but also for the characterization of other types of solid particles with complex morphologies.
The study of modern vegetation–pollen relationships has long been recognized as crucial for the proper interpretation of fossil pollen records. Despite the quickly growing number of palynological ...studies from central Iberia and its adjacent Atlantic margin, comprehensive studies about modern pollen representation at broad spatial scales were still lacking. In this paper, we have studied the vegetation–pollen relationships in the Tagus Basin in 62 sites located along a wide environmental gradient from Thermomediterranean evergreen mixed thermophilous woodlands by the Atlantic coast to Oromediterranean shrublands above the treeline in the Guadarrama Mountains (central Spain). At each site, we analyzed pollen from moss polsters and conducted vegetation surveys. Most forested vegetation types (pinewoods, oak woods, evergreen mixed thermophilous woodlands) presented rather distinct pollen assemblages dominated by the pollen equivalents of the major tree species. Nevertheless, enhanced taxonomic resolution within Pinus and Quercus ilex-type would represent significant progress, e.g., enabling to separate Mediterranean and mountain pinewoods. Pollen spectra from shrubland and steppic communities are in general less differentiated, due to high regional pollen input associated with low local pollen production and/or the dominance of insect-pollinated species (e.g., Cytisus oromediterraneus in mountain shrublands). The results presented here will readily assist the interpretation of regional fossil pollen records from small mires/bogs/lakes and forest hollows, given their comparable pollen catchments. Comparison of modern pollen assemblages with pollen records from larger lakes and marine settings is not so straightforward, but our results suggest that marine pollen assemblages might average the pollen signature of the entire basin.
•Pollen–vegetation relationships along broad environmental gradient in central Iberia.•Overall good match between dominant plant species and pollen equivalents in forests.•No distinct signature for communities dominated by insect-pollinated plants.•Data readily usable to interpret fossil records from small mires/bogs/forest hollows.
The Central Asian Orogenic Belt is complex and little understood in its geotectonic history. Here, we apply a new approach to conclude on the paleogeography of major Mongolian terrains using small ...skeletal fossil assemblages and a combined analysis of U‐Pb ages and typology of detrital zircons. We document a new Cambrian Stage 3 fauna from the Telmen Block located between the Dzhabkan and Tuva‐Mongolia cratons. Based on a hierarchical cluster analysis of 35 blocks, we observe the most robust biogeographic relationship between Telmen and Kusnetzk Alatau and between Tuva‐ Mongolia and Lake Zone. These results challenge the view that these cratons were assembled during the Ediacaran/Cambrian in a single ribbon‐shaped paleocontinent. Detrital zircon U‐Pb ages indicate a unique age population at ∼516 Ma at Telmen derived from I‐type granitoids, neither seen on Dzhabkan nor Tuva‐Mongolia cratons supporting their different tectonic evolution within the Palasian Ocean after the breakup of Rodinia.
Plain Language Summary
The Central Asian Orogenic Belt is the largest orogeny on Earth, with main orogenetic events spanning the late Cambrian to early Triassic (ca. 500–250 Ma) reaching from the Ural Mountains to the Pacific Ocean. It included many Proterozoic Terrains, part of which are situated in Mongolia. However, until now, little is known about the pre‐orogenic paleogeographic settings of these terrains. Here we investigated detrital zircon age populations and biogeographic relationships of small skeletal fossils of the Cambrian cover strata to conclude on the pre‐orogenic tectonic evolution of the terrains. U‐Pb ages of detrital zircons allowed us to compare age histograms of different blocks and draw interpretations of their source rocks. Studying the mineralized skeletal remains of various metazoan groups concludes their paleobiogeographic relationships within the Mongolian micro blocks. In particular, the Telmen Block provides new insights challenging the previous hypotheses on the existence of one large ribbon‐shaped continent before the onset of the orogeny. This study instead argues for individual tectonic and metazoan evolution pathways of early Cambrian Mongolian blocks after the breakup of the supercontinent Rodinia.
Key Points
Novel reconstruction tool for paleogeography of Mongolian Central Asian Orogenic Belt terrains using detrital zircon age provenance and small skeletal fossils
Rewriting the long‐held theory that the Mongolian terrains formed a single ribbon‐shaped continent during the Ediacaran/Cambrian
Zircon provenance and small skeletal fossils biogeography argue for individual tectonic evolution of Mongolian terrains from Ediacaran to early Cambrian
The biogeochemical cycles of carbon (C) and nitrogen (N) are inextricably linked for a range of reactions. For coupled reactions such as denitrification to occur, however, solutes must be found ...together in space and time. Using the framework of concentration-discharge (c-Q) relationships, we examine the frequency of synchronous C and N export (i.e. identical c-Q behavior) across a river network using > 5 years of high-frequency sensor data. We demonstrate that across space and time the export of C and N to a river network is asynchronous 57% of the time. The probability of simultaneous export in largely forested watersheds demonstrates little temporal structure, while in more human-impacted watersheds, we observe the highest frequency of asynchronous c-Q behavior. We discuss the implications of synchronous c-Q behavior for solute flux estimation models and develop a theoretical framework for predicting where within a landscape we expect the probability of coupled C and N reactions to be greatest. By simultaneously comparing the variability in C and N c-Q relationships we develop an integrated framework for predicting synchronous export of solutes.
The accumulation, distribution, and contamination status of metals in the Ömerli Dam sediments were investigated using ecotoxicological and human health indexes in this study. Identifying potential ...sources of waste metals in the sediments and assessing ecological risks, principal component analysis (PCA)/factor analysis (FA), hierarchical cluster analysis (HCA), enrichment factor (EF), geoaccumulation index (I
geo
), contamination factor (CF), potential load index (PLI), potential ecological risk index (Er
i
), modified hazard classification methods such as quotient (
m
HQ), toxic units (TUs), toxic risk index (TRI), integrated pollution index (IPI) methods are used. Potential health risks of toxic metals in sediment were designated by modified hazard quotient (
m
HQ), hazard index (HI), and total lifetime cancer risk (LCR) models. Besides, heavy metal concentrations and calculated index values were evaluated with spatial distribution maps using the IDW technique with GIS software. The average of metal concentrations was put in order as follows: (mg/kg) Al (74,290.39) > Fe (37,767.10) > Mn (484.20) > Zn (180.81) > Cr (117.26) > V (108.17) > Pb (94.76) > Ni (63.67) > Cu (53.11) > Co (15.65) > As (15.04) > Sb (1.86) > Cd (1.76) > Hg (1.30). Cr, Cu, Zn, As, Cd, Sb, Hg, and Pb average values are higher than the earth's crust's average values. According to EFs which is an indicator of anthropogenic inputs, EF
Cd
(7.34) and EF
Pb
(5.92) showed moderate–severe enrichment, and EF
Hg
(4.08) was moderate enrichment. PCA/FA and CA revealed that heavy metal contamination is affected by more than one source of pollution. HQ and HI values for each metal are less than 1 for children and adults. LCR values of Cd, Cr, Pb, and As are lower than the target risk level (1.00E-04). According to this study, more attention should be paid to the comprehensive risk assessment of metals in the sediment ecosystem for both aquatic biota and residents in the vicinity of the Ömerli Dam.
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•GDGTs in soil, in-cave surfaces and cave drip water analysed at two caves.•GDGT distributions differ between soils, in-cave surfaces and drip waters.•Global modern speleothem GDGTs ...distributions differ from these potential sources.•TEX86 is a robust speleothem GDGT paleothermometer recording cave temperature.•Improved understanding and measurement of cave temperatures is important.
The glycerol dialkyl glycerol tetraether (GDGT) paleothermometer has potential application as a speleothem paleoclimate proxy. However, the sources of GDGTs found in speleothems are poorly understood, with multiple potential sources of GDGTs from the soil to the speleothem surface. Here we analysed GDGTs in soils, soil leachates, in-cave surfaces and cave drip waters at two Australian montane caves. We observed significantly different GDGT distributions between soils, soil leachates, in-cave surfaces and drip waters and significant spatial differences in in-cave GDGT distributions. Comparison with published modern in-cave and karst groundwater GDGT datasets from Australia, Europe and China shows that speleothem GDGT distributions are different from those of all potential sources. We hypothesise that speleothem surfaces have a calcifying, alkaline, oxic, wet, carbon-available, environment that supports a microbial community that is different from other possible karst GDGT sources. We propose that the presence of GDGTs related to anoxic or methanogenic conditions, and observed in cave drip water and on in-cave surfaces, can be used to identify GDGTs from these sources. We confirm that TEX86 based paleothermometers are robust speleothem GDGT paleothermometers, whose calibration can be further refined through improved understanding and measurement of cave temperatures.
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