ALBERT

Description: Abstract Contractional deformation in the outer parts of fold‐and‐thrust belts is in part controlled by the presence of syntectonic sediments and multiple décollements (e.g. the Apennines, the Appalachians, the Pyrenees, the Zagros, or the Sub‐Andean and Kuqa fold‐and‐thrust belts). To better understand the influence of these parameters in the kinematic evolution of fold‐and‐thrust systems, we carried out an experimental study including four 3D sandbox models inspired by one of the previously mentioned prototypes, the Kuqa fold‐and‐thrust belt. This belt contains two décollements: a weak synorogenic salt layer; and a deeper, preorogenic and frictionless décollement (i.e., organic‐rich shales) showing along strike variations of rheology. The experimental results show that increasing synkinematic sedimentation rate: (i) generates a progressive change from distributed to localized deformation and, (ii) delays the development of frontal contractional structures detached on the salt, favoring the formation and reactivation of more hinterland thrusts and backthrusts. With respect to the rheology, our study reveals that as the viscosity of the prekinematic décollement increases: (i) the deformation propagates more slowly towards the foreland and, (ii) the underlying thrust stack becomes broader and lower and has a gentler thrust taper angle. The rheology of the prekinematic décollement defines the distribution and geometry of the structures detached on it that in turn influence the development of overlying, salt‐detached structures. Subsalt structures can: (i) determine the areal extent of the salt and therefore of any fold‐and‐thrust system detached on it and, (ii) hamper or even prevent the progressive foreland propagation of deformation above the salt.

Description: Abstract The scombrids (Family Scombridae), commonly known as tunas, bonitos, Spanish mackerels, and mackerels, play an important role as predators and prey in coastal and oceanic marine ecosystems, and sustain some of the most important fisheries in the world. Knowledge of their basic biology and life history traits, such as growth, age and maturity, is fundamental to sustainably manage these species, and maintain their critical role in marine ecosystems. Given the economic and social importance of their fisheries in many regions throughout the world, numerous life history studies have been conducted in the last century. Despite efforts to create global repositories of life history parameters, e.g. FishBase, many life history studies remain scattered and not readily accessible. Here, we compiled 667 life history studies published between 1933 and 2012 describing the growth, age, and reproductive biology of the 51 species of scombrids distributed around the world and create a standardized life history dataset including maximum size, longevity, growth, maturity, fecundity, spawning season and frequency, and egg size information. We created this dataset to promote the best use of the existing life history information and with the intention of providing a data resource suitable to test large‐scale ecological hypotheses on life history strategies and life history evolution, as well as support the management and conservation of this important group of commercially exploited species. We envisage the large repository of standardized life history data compiled will make this endeavor more effective and robust by providing a valuable resource that can help address many research questions. This article is protected by copyright. All rights reserved.

Description: Abstract The study of the coastal landscapes of hotspot oceanic islands through comprehensive structural metrics and ecological estimators represents an opportunity to explore geomorphological transformations and broad spatiotemporal scale features of coastal evolution. As part of this approach, a new metrical comparative analysis is presented in this study, comprising four islands in different evolutionary stages. They belong to the Cape Verde archipelago, which forms a double insular chain in which an east‐west gradient in age and evolution is particularly evident across the southern chain. A space‐for‐time (SFT) substitution approach is applied to the coasts of (1) Fogo, in the shield stage; (2) Santiago, in the early post‐erosional stage; (3) São Vicente, in the advanced post‐erosional stage; and (4) Boa Vista, in the last erosional stage. From the obtained spatial distributions and frequencies of landforms, the coastal landscapes of these islands are compared in relation to their (i) geomorphic composition, using similarity indices (Whittaker, βw, Sorensen, Cs) and nestedness estimators (NOFD, WNODF), (ii) geomorphic abundance, using morpho‐assembling densities (Dgm), and (iii) geomorphic diversity, using six alpha‐diversity indices (Richness, S, Menhinick, DMN, Simpson, D, Shannon, H', Berger‐Parker, d, and Brillouin, HB). An advanced geomorphological taxonomy is implemented for areas with limited open‐access data, including a set of planform features captured through scale‐frequency decomposition. Photographic, cartographic and field work data are used for landform identification at 1,200 random sampling points, empirically determined by a bootstrap method. The results show a chronological ordering of the compared variables and a possible co‐evolution towards an increase in organizational geomorphic complexity of coastal systems at broad space‐time scales. The method proposed in this study can contribute, from a metrical perspective, to finding new long‐term evolutionary features and constitutes an advance in the development of an integrated model of coastal evolution in oceanic islands.

Description: Gravel-bed rivers commonly exhibit a coarse surface armor resulting from a complex history of interactions between flow and sediment supply. The evolution of the surface texture under single storm events or under steady flow conditions has been studied by a number of researchers. However, the role of successive floods on the surface texture evolution is still poorly understood. An experimental campaign in an 18 m-long 1 m-wide flume has been designed to study these issues. Eight consecutive runs, each one consisting of a low-flow period of variable duration followed by a sudden flood (water pulse) lasting 1.5 h, have been conducted. The total duration of the experiment was 46 h. The initial bed surface was created during a 280 h-long experiment focused on the influence of episodic sediment supply on channel adjustments. Our experiments represent a realistic armored and structured beds found in mountain gravel-bed rivers. The armor surface texture persists over the duration of the experiment. The experiment exhibits downstream fining of the bed surface texture. It was found that sorting processes were affected by the duration of low-flow between flood pulses. Since bedload transport is influenced by sediment sorting, the evolution of bedload transport is impacted by the frequency of the water pulses: short inter-pulse durations reduce the time over which fine material (transported as bedload) can be winnowed. This, in turn, contributes to declining reduction of the bedload transport over time while the sediment storage increases. This article is protected by copyright. All rights reserved.

Description: Dam removal has been demonstrated as one of the most frequent and effective fluvial restoration actions but at most dam removals, especially of small dams, there has been little geomorphological monitoring. The results of the geomorphological monitoring implemented in two dams in Urumea and Leitzaran Rivers (northern Spain) are presented. The one from Urumea River, originally 3.5 m high, impounded 500 m of river course, was removed instantaneously whereas that in Leitzaran River, was 12.5 m high, impounded 1,500 m of river course, and it is in its second phase of a 4-stage removal process. Changes in channel morphology, sediment size and mobility and river bed morphologies were assessed. The monitoring included different techniques: topographical measurements of the channel, terrestrial laser scanner measurements of river bed and bars, sediment grain size and transport; all of them repeated in four (May, August, November 2011 and May 2012) and five (July and September 2013, April and August 2014 and June 2015 fieldwork campaigns in Urumea and Leitzaran Rivers, respectively. Geomorphic responses of both dam removals are presented, as well as compared between them. Morphological channel adjustments occurred mainly shortly after dam removals, but with differences among the one removed instantaneously, that was immediate, whereas that conducted by stages took longer. Degradational processes were observed upstream of both dams (up to 1.2 m and 4 m in Urumea and Leitzaran Rivers, respectively), but also aggradational processes (pool filling), upstream of Inturia dam (2.85 m at least). Less evident aggradational processes were observed downstream of the dams (up to 0.37 m and 0.50 m in Urumea and Leitzaran Rivers, respectively). Flood events, specially a 100-year one registered during the monitoring period of Mendaraz dam removal, reactivated geomorphological processes as incision and bank erosion, whereas longitudinal profile recovery, grain-size sorting and upstream erosion took longer. This article is protected by copyright. All rights reserved.

Description: Longitudinal profiles of alluvial rivers usually exhibit upward-concave curvatures at equilibrium. River profile concavity has been primarily attributed to sediment downstream fining and to streamwise increments of water discharge. Conversely, upward-convex profiles have been typically associated with tectonic and geologic controls and with outlet base-level drops. Equations to describe river profiles at equilibrium developed from mass conservation principles do not consider longitudinal changes in channel width. This study addresses how variations in channel width can also act to control the curvature of longitudinal profiles. We develop a new theoretical framework in which the role on river profiles of downstream variations of channel width, flow discharge, bed roughness, and surface texture are explicitly shown. Unlike classical approaches for river profile evolution, this novel framework identifies physical domains for rivers to develop upward-concave/convex longitudinal profiles depending on channel width and flow discharge gradients flow intensity and surface texture.

Description: Using the state-of-the-art emissions-driven Max-Planck-Institute Earth system model, we explore the impacts of artificial ocean alkalinization (AOA) with a scenario based on the Representative Concentration Pathway (RCP) framework. Addition of 114 Pmol of alkalinity to the surface ocean stabilizes atmospheric CO 2 concentration to RCP4.5 levels under RCP8.5 emissions. This scenario removes 940 GtC from the atmosphere and mitigates 1.5 K of global warming within this century. The climate adjusts to the lower CO 2 concentration preventing the loss of sea-ice and high sea level rise. Seawater pH and the carbonate saturation state (Ω) rise substantially above levels of the current decade. Pronounced differences in regional sensitivities to AOA are projected, with the Arctic Ocean and tropical oceans emerging as hot spots for biogeochemical changes induced by AOA. Thus, the CO 2 mitigation potential of AOA comes at a price of an unprecedented ocean biogeochemistry perturbation with unknown ecological consequences.

Description: This paper presents the results of a Gilbert-type delta progradation experiment within an impoundment created by a dam. The delta was composed of a poorly-sorted sand-gravel mixture in a bedload-dominated environment. The main goal of the paper is to analyze the sorting process of material within the deposit as the delta progrades towards the dam. Bed profile evolution has been documented and the entire delta has been extensively sampled in order to study sorting processes. Longitudinal and vertical sorting mechanisms are illustrated. What is novel in this investigation is the complete record, within an entire deltaic deposit, of the vertical distribution of streamwise sorting in the absence of suspended load. The data presented herein provide a detailed description of sorting processes in a Gilbert-type delta. The experimental set-up, the water flow and the sediment feed rate chosen determine the evolution of the delta: it initially progrades with little topset aggradation and degrades afterwards. Experimental results fit well with a previously-presented empirical sorting model, in spite of the fact that the experimental conditions used here were well outside the range of those used to derive that model. The relative coarsening of the upper layers of the delta is found to be related to the slow speed at which the delta progrades, the formation of a mobile armour layer and the erosion of the topset towards the end to the run. Furthermore, a strong correlation between the coarsening of the bottom layer of the delta and its front height has been documented and explained: as the delta gets higher, since there is more space to sort sediment, it is more likely that coarse particles failing near the top of the foreset reach the bottom of the foreset. These findings provide new and useful data documenting sediment sorting in granular, bedload-dominated deltas. This article is protected by copyright. All rights reserved.

Description: The scombrids (Family Scombridae), commonly known as tunas, bonitos, Spanish mackerels, and mackerels, play an important role as predators and prey in coastal and oceanic marine ecosystems, and sustain some of the most important fisheries in the world. Knowledge of their basic biology and life history traits, such as growth, age and maturity, is fundamental to sustainably manage these species, and maintain their critical role in marine ecosystems. Given the economic and social importance of their fisheries in many regions throughout the world, numerous life history studies have been conducted in the last century. Despite efforts to create global repositories of life history parameters, e.g. FishBase, many life history studies remain scattered and not readily accessible. Here, we compiled 667 life history studies published between 1933 and 2012 describing the growth, age, and reproductive biology of the 51 species of scombrids distributed around the world and create a standardized life history dataset including maximum size, longevity, growth, maturity, fecundity, spawning season and frequency, and egg size information. We created this dataset to promote the best use of the existing life history information and with the intention of providing a data resource suitable to test large-scale ecological hypotheses on life history strategies and life history evolution, as well as support the management and conservation of this important group of commercially exploited species. We envisage the large repository of standardized life history data compiled will make this endeavor more effective and robust by providing a valuable resource that can help address many research questions. This article is protected by copyright. All rights reserved.

Description: The long‐term evolution of coastal geomorphic structure is examined by analyzing and comparing the geomorphological composition, abundance and diversity of the coasts of three hot‐spot islands in different stages of development. A pattern of change in the geomorphological composition was observed, associated with an increasing coastal geomorphic abundance and diversity from the youngest to the oldest island. This may provide a new interpretation of the coastal evolution on hot‐spot oceanic islands. Abstract The Canary Islands form a volcanic archipelago in which a west–east (W–E) chain of progressively older and less active islands can be observed. In the Canary Islands, unlike most hot‐spot archipelagos, certain geodynamic peculiarities have promoted longer periods of island survival, exceeding 20 Myr. This factor makes these islands a suitable context for this work, which aims to analyze extensively the coastal geomorphic structure on islands with different development states. For this, three islands in different volcanic phases were selected: La Palma (1.8 Myr), Gran Canaria (14.5 Myr) and Fuerteventura (22.6 Myr). An ad hoc landform‐based hierarchical taxonomy was designed to analyze the coastal geomorphic structure of the three islands. Based on a multi‐sourced analysis in geographic information system (GIS) and field recognition, a comprehensive cartographic database was collected using the coastline data‐storing (CDS) method as a feature abundance proxy. Three different aspects of the geomorphological structure were compared and related between the islands: (i) composition, (ii) abundance and (iii) diversity. Through their comparison, we attempt to explore geomorphological aspects of coastal evolution over geological spatiotemporal scales. Composition was explored analyzing the distribution of the feature's longshore frequencies (p). Abundance, by metrics of local abundance (N∩) and whole density (NU). Diversity, through four indices: normalized richness (S) and Margalef index (M) to estimate richness; Simpson index (D) and Shannon index (H’) to estimate evenness. We identified a systematic transformation in the dominant landform composition and a systematic trend in increasing geomorphological abundance and diversity from younger to older islands. The results show a long‐term structural pattern defined by the increase in coastal geomorphic complexity (abundance and diversity) over geological time, as the coasts evolve from predominantly rocky‐erosive to increasingly clastic‐depositional environments. This long‐term geomorphological pattern may be a general aspect of hot‐spot island archipelagos, which can bring a new perspective to the knowledge of their coastal evolution. © 2018 John Wiley & Sons, Ltd.