ALBERT

Description: Palynological and sedimentological studies were performed at two Holocene profiles in erosion gullies (Ze’elim and Ein Feshkha) which dissect the retreating western shore of the Dead Sea. The aim of the project was to analyse possible links between climate, lithology, and vegetation development. The section in Ze’elim shows both lacustrine and fluvial sediments, whereas sedimentation at Ein Feshkha is predominantly lacustrine. The Ze’elim profile, previously used for paleo-lake reconstruction provides an opportunity to compare climate triggered lake levels as paleo-hydrological indicators and vegetation history by use of palynology. The vegetation development in Ze’elim and Ein Feshkha is influenced by both climate and human impact. The pollen record of Ze’elim begins in the Pottery Neolithic, the section of Ein Feshkha in the Late Bronze Age, both records end in the Middle Ages. The Ze’elim section is characterized by sedimentary hiati between the beginning of the Chalcolithic Period until the Middle Bronze Age and within the Late Bronze Age. Settlement periods during the Middle Bronze Age, Iron Age and Hellenistic–Roman–Byzantine Period are indicated by high values of anthropogenic indicators and/or Mediterranean trees. Collapses of agriculture, which can be related to climate effects, are evident during the Late Bronze Age, during the Iron Age and at the end of the Byzantine Period when the lake level curve indicates arid conditions. A comparison of the two pollen records, from different environments, illustrates a more prominent influence of Mediterranean vegetation and cultivated plants in the pollen diagram of Ein Feshkha. The southern Dead Sea region (at the desert fringe) is more vulnerable to regional climate change.

Description: The influence of plate boundary curvature on the large-scale stress and strain patterns in an overriding plate is explored using 2D numerical and 3D thermo-mechanical analogue experiments. Numerical experiments reveal that trench-parallel compression is produced near the symmetry axis of a seaward-concave plate boundary if in- terplate friction is high and/or the subducting lithosphere has a low flexural rigidity. In contrast, trench-parallel compression is reduced along the oblique parts of the plate boundary. However, both the stress conditions on the interplate zone and the 3-D geometry of this zone control whether the trench-parallel stress in the centre of the curvature is a tension or compression. Low dip angle and high convergence obliquity angle favour trench-parallel compression. In the central Andes, N-S minor shortening in the centre of the Arica bend and strike slip systems north and south of the symmetry axis suggest that the effect of shear traction dominated during Cenozoic time when the curvature of the plate boundary was forming. We therefore argue that the processes responsible for the formation of the plate boundary curvature were assisted by enhanced interplate friction and/or reduced compres- sive non-hydrostatic normal stress. 3D thermo-mechanical laboratory experiments of oceanic subduction along a seaward-concave plate boundary are performed in order to investigate the large-scale deformation pattern in the upper plate. However, model deformation was restricted to the fore-arc domain because high friction was only im- posed in the upper, shallow (0-50 km) part of the interplate zone. Nevertheless, the large-scale deformation pattern shows characteristics which fit observations in the Andes. Along the oblique section of the plate boundary, oblique subduction produces trench-parallel shearing of the fore-arc towards the centre of the curvature, significant trench- normal coaxial shortening but little to no trench-parallel coaxial shortening. This explains the excess-rotation obtained from paleomagnetic data and kinematic models. In contrasts, fore-arc deformation near the centre of the curvature includes the largest trench-normal coaxial shortening, significant trench-parallel coaxial shortening but no trench-parallel shearing. This strain pattern also corresponds to that obtained from kinematic models. Impor- tantly, the model deformation reveal that trench-normal coaxial shortening is locally shifted inland because of the trench-parallel coaxial shortening occurring in the frontal part of the fore-arc. We therefore argue that this pattern is an intrinsic characteristic of the 3D deformation along seaward-concave plate boundary due to high interplate friction. This characteristic may extend to the arc/back-arc deformation if the high interplate friction is extended further down the interplate zone and the entire fore-arc block is dragged laterally instead of only its frontal part.

Description: Heat flow measurements collected throughout the Auka and JaichMaa Ja'ag' hydrothermal vent fields in the central graben of the Southern Pescadero Basin, southern Gulf of California, indicate upflow of hydrothermal fluids associated with rifting dissipate heat in excess of 10 W/m2 around faults that have a few kilometers in length. Paradoxically, longer faults do not show signs of venting. Heat flow anomalies slowly decay to background values of ∼2 W/m2 at distances of ∼1 km from these faults following an inverse square-root distance law. We develop a near-fault model of heat transport in steady state for the Auka vent field based on the fundamental Green's function solution of the heat equation. The model includes the effects of circulation in fracture networks, and the lateral seepage of geothermal brines to surrounding hemipelagic sediments. We use an optimal fitting method to estimate the reservoir depth, permeability, and circulation rate. Independently derived constraints for the model, indicate the heat source is at a depth of ∼5.7 km; from the model, permeability and flow rates in the fracture system are ∼10−14 m2 and 10−6 m/s, respectively, and ∼10−16 m2 and 10−8 m/s in the basin aquitards, respectively. Model results point to the importance of fault scaling laws in controlling sediment-hosted vent fields and slow circulation throughout low permeability sediments in controlling the brine's chemistry. Although the fault model seems appropriate and straightforward for the Pescadero vents, it does seem to be the exception to the other known sediment-hosted vent fields in the Pacific.

Description: The linear discriminant analysis (LDA) is a common technique used in machine learning and pattern recognition for dimensionality reduction problems. Here, the LDA is applied to detect faults-scarps in high-resolution bathymetric profiles in the Southern Pescadero Basin (SPB) in the Gulf of California. The LDA uses fault scarps and cuestas (sloping topography) identified by a geomorphologist in the neighboring Alarcón Rise (AR). These geometric representations are transformed into a parametric space by an idealized fault-scarp degradation model. Through inversion, we extracted the product of the mass diffusion coefficient with time (τ), scarp height (u0), and goodness of fit of the model on the scarp profiles and cuestas (ε). The LDA transforms the parametric space τ, u0, ε by the Fisher’s criterion into a 1D dimensional space that maximizes separability of classes. Then, the classification is performed by Bayes decision rule using the probability density functions (PDF) built from the 1D projected data for each class (fault-scarps and cuestas). The implementation results in cross-sectional profiles across the SPB show the ability to detect faults in the deepest part of the basin where the flat basin floor is interrupted by morphologically young fault-scarp arrays. The LDA interpretation outperforms manual identification, particularly in faults scarps that are longer than ∼3 km, whereas shorter faults are challenging to discern from other linear features like channels. The model can extract information about the state of degradation of the scarps. This application allows the identification of fault generation episodes and resolves kinematic interactions between faults.

Description: This article is composed of two independent opinion pieces about the state of integrated, coordinated, open, and networked (ICON) principles (Goldman et al., 2021, https://doi.org/10.1029/2021EO153180; Goldman et al., 2022, https://doi.org/10.1029/2021ea002099) in Tectonophysics and discussion on the opportunities and challenges of adopting them. Each opinion piece focuses on a different topic: (a) global collaboration, technology transfer and application, reproducibility, and data sharing and infrastructure; and (b) field, experimental, remote sensing, and real-time data research and application. Within tectonophysics science, ICON-FAIR principles are starting to be adopted and implemented, however they have not become frequent and there are still plenty of opportunities for further development. During the last decade, standardization reduced fragmentation, facilitated openly available databases, and enabled different modeling methods to be combined. On the other hand, integration and coordination remained insufficient as exemplified by numerous geophysical interpretation programs running on different platforms, lacking the proper documentation and with diverse output formats. We agree that adapting the principles of ICON-FAIR brings high efforts and risks, but in the end, it has great benefits and potential in the tectonophysics community.

Description: A primary control on the geodynamics of rifting is the thermal regime. To better understand the geodynamics of rifting in the northern Gulf of California we systematically measured heat-flow across the Wagner Basin, a tectonically active basin that lies near the southern terminus of the Cerro Prieto fault. The heat flow profile is 40 km long, has a nominal measurement spacing of ∼1 km, and is collocated with a seismic reflection profile. Heat flow measurements were made with a 6.5-m violin-bow probe. Although heat flow data were collected in shallow water, where there are significant temporal variations in bottom water temperature, we use CTD data collected over many years to correct our measurements to yield accurate values of heat flow. After correction for bottom water temperature, the mean and standard deviation of heat flow across the western, central, and eastern parts of the basin are 220 ± 60, 99 ± 14, 889 ± 419 mW m−2, respectively. Corrections for sedimentation would increase measured heat flow across the central part of basin by 40 to 60%. We interpret the relatively high heat flow and large variability on the western and eastern flanks in terms of upward fluid flow at depth below the seafloor, whereas the lower and more consistent values across the central part of the basin are suggestive of conductive heat transfer. Moreover, heat flow across the central basin is consistent with gabbroic underplating at a depth of 15 km and suggests that continental rupture here has not gone to completion.