Adjacent Canyons Research Articles

Sediment flux variation as a record of climate change in the Late Quaternary deep‐water active Corinth Rift, Greece

AbstractThe value of deep‐water sedimentary successions as reliable records of environmental change has been questioned due to their long response times and sediment pathways leading to complex responses to climatic change and tectonic signals over differing timescales. We studied the Gulf of Corinth, Greece, to test the value of deep‐water stratigraphic successions as records of external controls on sediment flux in a setting with short response times and transport distances. The confinement of the rift basin allows for a near‐complete accounting of clastic sediment volumes. The recent acquisition of high‐resolution seismic reflection data, utilisation of International Ocean Discovery Programme Expedition 381 cores and a robust chronological framework, enable evaluation of the stratigraphy at a high temporal resolution. Combining borehole and high‐resolution seismic reflection data, distinct seismic units can be correlated to multiple paleoenvironmental proxies, permitting quantification of sediment flux variation across successive glacial–interglacial cycles at ca. 10 kyr temporal resolution. Trends in average sediment flux since ca. 242 ka show ca. 2–9 times greater sediment flux in cooler glacials compared to warmer interglacial conditions. The Holocene is an exception to low sediment flux for the interglacials, with ca. 5 times higher rates than previous interglacials. The short and steep configuration of the Sythas canyon and its fan at the base of an active submarine normal fault results in deep‐sea deposition at all sea‐level stands. In contrast, adjacent canyon systems shut down during warm intervals. When combined with palynology, results show that periods of distinct vegetation re‐organisation correlate to sediment flux changes. The temporal correlation of sediment flux to palynology in the Gulf of Corinth over the last ca. 242 kyr is evidence that variability of sediment supply is largely governed by climate‐related changes in hinterland catchments, with sea‐level and tectonics being second‐order controls on sediment flux variability.

At the base of deep-sea food webs: Assemblage and trophic structure of suprabenthos and zooplankton in submarine canyons

Submarine canyons act as hotspots of biodiversity, hosting vulnerable marine ecosystems, and playing a fundamental role in bridging coastal zones with deeper areas. Here, we investigated the suprabenthic and Deep Scattering Layer (DSL) zooplankton fauna, that play a key role in deep-sea food webs, as main resources for both mobile and sessile megafauna, in two submarine canyons (Squillace and Amendolara) of the Ionian Sea (Central Mediterranean Sea). Our results highlighted different taxonomic and functional diversity between the two adjacent canyons: (i) biomass and abundance of suprabenthos followed an opposite trend in the two canyons, increasing both with depth in Amendolara (higher abundance and biomass in the lower part of the canyon), and decreasing with depth in Squillace (greater in the head of the canyon); (ii) DSL zooplankton abundance and biomass followed a spatial distribution, decreasing with increasing distance from the coast for both canyons (i.e. lower offshore than at the head of the canyon). Food-web structure investigated by means of stable isotope analysis of δ13C and δ15N showed a more diverse trophic niche for suprabenthos than for zooplankton. Furthermore, possible feeding modes of species with unknown feeding behaviour have been proposed. The results of the current article highlight the different ecological processes occurring within each canyon. Understanding the spatial variations of communities inhabiting submarine canyons, especially those at the base of deep-sea food webs which can act as driver of megafaunal communities (both sessile and mobile-commercial species), is essential to focalise future conservation efforts.

Morphology and Depositional Processes of a Carbonate-Filled Canyon in the Carboniferous KT-II Formation of the Eastern Precaspian Basin, Kazakhstan: Insight from 3D Seismic Data

Canyons in carbonate depositional settings, as important elements of the source-to-sink system, remain poorly studied compared to those in siliciclastic depositional environments. The latest high-resolution three-dimensional seismic data, well logs, and core data at the eastern edge of the Precaspian Basin are used to investigate the geomorphology, infillings, and depositional process of a unique carbonate-filled canyon in the Carboniferous KT-II formation parallel to the carbonate platform, which is distinct from other slope-perpendicular canyons. The canyon has a total length of more than 52.3 km with a nearly N-S orientation and an S-shaped geometry, and the whole canyon can be divided into three segments by two knickpoints. The slope-parallel orientation of the canyon is mainly controlled by the palaeogeomorphology and reverse faults. Due to the collision of the Kazakh and European plates in the early-middle Visean (early Carboniferous), the canyon was formed in a northern tilted, elongated, and restricted palaeotopographic feature between uplifts. The development of reverse faults related to tectonic movement controlled the variations in the width of the canyon and the positions of the knickpoints. Tectonics controlled the orientation and formation of the canyon, while sedimentary processes contributed to its infilling. The well-seismic tie analysis indicated two distinct periods of the canyon fillings, Ss1 and Ss2, which were separated by a second-order sequence boundary. The lower part contained sediments supplied by both sides of the canyon through channels or gullies, and the upper part was dominated by a carbonate platform that prograded from the eastern side of the canyon. The evolution of the canyon can be subdivided into three stages. The increasing stage was mainly characterized by significant upslope erosion through headward retrogressive mass failures in the slope-parallel confined negative relief to form the canyon during the lowstand system tract of Ss1. Subsequently, in the early filling stage, the carbonate factory was productive during the highstand, and massive excess carbonate sediments were transported into the adjacent canyon by channels or gullies on both sides and deposited. The canyon was basically filled, and the morphology became much gentler. During the subsequent late filling stage, the carbonate platform was flooded again during the highstand, and the production rates of the carbonate factory greatly increased. The lateral progradation of carbonate platforms accelerated on the canyon of the early filling stage and further into the inner sag.

Air exchange rate and pollutant dispersion inside compact urban street canyons with combined wind and thermal driven natural ventilations: Effects of non-uniform building heights and unstable thermal stratifications

In the present work, a delicate CFD research of a multi-street canyon model with varying thermal stratifications and non-uniformities of buildings was conducted to investigate the street ventilation and pollutant dispersion between the compact urban blocks. Non-isothermal turbulent wind flow, temperature field and pollutant dispersion in a two-dimensional computational domain were solved by the Renormalization Group (RNG) k-ε turbulence model along with the enhanced wall treatment. Present numerical results indicated that the variation of ground heating intensity has a significant influence on the airflow pattern in the step-down case, and the distribution of pollutants in the street canyons mainly depends on the variation of the upper clockwise vortex. The canyon ventilation performance became better as the unstable thermal stratification strengthened. Similarly, the increase of ground heating intensity could reduce ADF (atmospheric dispersion factor) in the step-down case and ADF became the lowest when Ri = −3.92 was maintained. Additionally, the increase of building unevenness further complicated the canyon airflow structure, which aggravated the pollution of the canyon. In the step-down configuration, as the standard deviation of adjacent building height gradually increases, canyon ventilation could be further enhanced. For the step-up configuration, the best ventilation performance was found at σH = 16.7 %. ADF of adjacent canyons also varied greatly. When σH = 33.3 % was maintained, the peak and bottom values of ADF were discovered in the step-up and step-down cases, respectively. Present research has provided a theoretical reference for guiding urban design and improve living environment in modern compact cities.

The roles and seismic expressions of turbidites and mass transport deposits using stratigraphic forward modeling and seismic forward modeling

• Mass transport is more efficient than turbidity current in forming submarine canyons . • Turbidites are inside the river-fed systems as jigsaw puzzle geometries vertically. • MTDs are not constrained by river-fed systems and tend to occur in the bottom. • MTDs have chaotic or transparent seismic facies with irregular, massive thick shapes. • Turbidites have high amplitude seismic facies with sheet, mound or channel shapes. Turbidity currents and mass transport are two principal processes in deepwater settings. However, their roles in shaping deepwater depositional systems and interpreting their deposits in seismic profiles have not been fully settled due to the lack of extensive well data and high-quality seismic data in comparison with onshore oil fields. Therefore, this study integrated stratigraphic forward modeling (SFM) and seismic forward modeling to differentiate between the contributions of turbidity currents and mass transport as well as their seismic expressions. The workflow firstly compared three single-scenario SFM models, Model A (mass transport active), Model B (turbidity currents active), Model C (both active) to explore their contributions and interplay. Secondly, a multi-process and multi-scenario SFM model, Model D, is discussed with special emphasis on canyons. Thirdly, synthetic seismic profiles are generated via seismic forward modeling using the outcomes of the second step, then compared with actual seismic facies to verify the reliability. Through the abovementioned three steps, this study reveals that mass transport plays a major role in initiating canyons whereas turbidity currents act mainly as the reworking process. Turbidites are usually confined to shelf-incised canyons and adjacent canyons fed by terrestrial systems. Mass transport deposits (MTDs) are mainly distributed on the bottom of canyons and deep basins, forming the base boundary of each depositional cycle. A total of 14 synthetic seismic facies are identified. The comparison with actual seismic data shows that modeling results are similar to equivalent actual seismic features. This study helps to predict the spatial emplacement of MTDs and turbidites and interpret deepwater seismic data.

Different types of gravity-driven flow deposits and associated bedforms in the Upper Bengal Fan, offshore Myanmar

This study uses 3D reflection seismic data to investigate how sediment gravity flows contribute to the evolution of the lower continental slope of the Myanmar margin that is part of the Bengal Fan, the largest deep-water fan system in the world. Seafloor and subseafloor data show large sediment wave fields that developed on both flanks of an extensive submarine canyon. The sediment waves exhibit asymmetric stoss and lee sides, wave lengths and heights of 850–3000 m and 25–70 m, respectively, and an upslope direction of migration. Seismic data reveals the presence of multiple fields of vertically stacked sediment waves, interbedded with units characterised by a chaotic seismic facies that accumulate mainly in the troughs of the sediment waves and can be tracked laterally to the adjacent canyons. According to their seismic facies, geometry, and internal architecture these chaotic units are interpreted as debrites. Seismic attributes extracted from different horizons indicate that the sediment waves are dominated by fine-grained sediment, while the debrites are probably associated with coarser-grained deposits. The debrites fill the troughs of the sediment waves, as well as the downstream portions of canyon thalweg, thus flattening the paleo-seafloor. The sediment waves are interpreted as cyclic steps formed by low-density turbidity currents flowing across the slope down to the basin floor, where the change in gradient favours the formation of hydraulic jumps and the transition from supercritical to subcritical flow conditions. A conceptual model for the sediment wave evolution was proposed for the study area, in the transitional environment on the lower slope, with low-density gravity flow deposits and high-density debris flow deposits alternatively accumulating on the major gravity flow conduits.

Discovery of the Baldy toreva near urban areas along the southern Wasatch Range, Utah

ABSTRACTStructural and geomorphic studies, and lithostratigraphic and biostratigraphic mapping reveal that a giant toreva block (6.125 km3) slid off Mount Timpanogos toward what are now densely populated urban areas along the Wasatch Front of Utah. The block forms a prominent peak known as Big Baldy, which consists of steeply dipping and locally brecciated limestone and quartzarenite over nearly horizontal shale. Preferential erosion of this shale below overlying limestone and quartzarenite cliffs is most likely the cause of this particular landslide and potential future slides along the Wasatch Front. The low-angle contact at the base of the giant toreva block was initially mapped as a thrust, then as a low-angle normal fault. In both cases, these faults were inferred to have large amounts of displacement (900 meters), but no traces of such faults are found in adjacent canyons. The Baldy slide is associated with geomorphologic features, such as faceted spurs, landslide scarps, sackungen, and hummocky terrain. Limestone and quartzarenite beds in the block are back-rotated up to 80° and are locally broken and brecciated. No evidence of hydro-fracturing is found in the breccia or of multiple brecciation episodes, which indicates surficial rather than deep-crustal processes and perhaps a single event of slip. We speculate based on structural reconstructions of the slide block, and interpolation of maximum downcutting rates on nearby streams, that the slide initiated between 700 and 500 ka. Discovery of the Baldy slide attests to the importance of recognizing the influence of surficial processes in mountain front development and demonstrate the ongoing geologic hazard of mass wasting to communities along the seismically active Wasatch Front and similar horst blocks.

Continental slope and rise geomorphology seaward of the Totten Glacier, East Antarctica (112°E-122°E)

The continental slope and rise seaward of the Totten Glacier and the Sabrina Coast, East Antarctica features continental margin depositional systems with high sediment input and consistent along-slope current activity. Understanding their genesis is a necessary step in interpreting the paleoenvironmental records they contain. Geomorphic mapping using a systematic multibeam survey shows variations in the roles of downslope and along slope sediment transport influenced by broad-scale topography and oceanography. The study area contains two areas with distinct geomorphology. Canyons in the eastern part of the area have concave thalwegs, are linked to the shelf edge and upper slope and show signs of erosion and deposition along their beds suggesting cycles of activity controlled by climate cycles. Ridges between these canyons are asymmetric with crests close to the west bank of adjacent canyons and are mostly formed by westward advection of fine sediment lofted from turbidity currents and deposition of hemipelagic sediment. They can be thought of as giant levee deposits. The ridges in the western part of the area have more gently sloping eastern flanks and rise to shallower depths than those in the east. The major canyon in the western part of the area is unusual in having a convex thalweg; it is likely fed predominantly by mass movement from the flanks of the adjacent ridges with less sediment input from the shelf edge. The western ridges formed by accretion of suspended sediment moving along the margin as a broad plume in response to local oceanography supplemented with detritus originating from the Totten Glacier. This contrasts with interpretations of similar ridges described from other parts of Antarctica which emphasise sediment input from canyons immediately up-current. The overall geomorphology of the Sabrina Coast slope is part of a continuum of mixed contourite-turbidite systems identified on glaciated margins.

Semi-Arid Shrublands Require Little On-Going Management to Remain Suitable for Black-Capped Vireos

The recently delisted black-capped vireo (Vireo atricapilla, hereafter “vireo”) nests in shrublands from south-central Oklahoma to southwestern Tamaulipas, Mexico. Vireos are considered to be “conservation-reliant” because they require on-going habitat maintenance and control of brown-headed cowbirds (Molothrus aster, hereafter “cowbird”). Most long-term research has been conducted in comparatively mesic parts of the vireo range, but more arid shrublands comprise the larger proportion of their distribution. Our study area is in a Nature Conservancy preserve in southwestern Texas (Val Verde County), which does not manage vireo habitat or cowbird populations. We examined change in habitat characteristics (2002 vs 2017) and bird detections (1997-2001 vs 2013-2017) at two sites: a mesic alluvial terrace and an adjacent semi-arid canyon. The alluvial site is recovering from a historic flood in the 1950s that scoured vegetation to bare ground; the canyon site has not experienced any major disturbance in that time frame. Vireo and cowbird detections declined at the alluvial site but not at the canyon site. Several important vegetation characteristics of the alluvial site changed significantly: density of leaf cover at lower heights (<1 m) decreased, the number of shrubs increased, and tree height increased. At the canyon site, leaf density increased in all height classes above 0.5 m, shrub width increased, and the number of shrubs increased. While the alluvial site has become less suitable for vireos, the canyon site has supported breeding vireos throughout our study period despite lack of landscape management or cowbird control. Our data suggest that in more arid parts of the vireo range, undisturbed shrublands persist as mature viable habitat for extended periods, possibly in perpetuity, with little or no need for management. These low-maintenance shrublands will be especially important for the long-term persistence of black-capped vireo populations.

Survival of Juvenile &amp;lt;i&amp;gt;Acer grandidentatum&amp;lt;/i&amp;gt; Nutt. (Bigtooth Maple, Aceraceae) in Central Texas Woodlands

Populations of Acer grandidentatum Nutt. (Bigtooth maple, Aceraceae = Sapindaceae) in central Texas are mostly found in isolated, deep, relatively remote, limestone canyons. Acer grandidentatum is found with a few other mostly deciduous species. Recruitment of juveniles has been reported to be lacking. One population of A. grandidentatum juveniles was found in a limestone canyon in a State Natural Area in Central Texas. Fifty juveniles were located. Wire enclosures were placed around half of the seedlings with half left in the open. In an adjacent canyon, 50 juvenile seedlings were planted in a similar habitat with adult A. grandidentatum trees nearby. Half were in enclosures and half in the open. Plant survival was followed for four growing seasons until November 2019. At the end of that time when survivals were compared between plants in enclosures and those in the open in both canyon communities, there was a significant difference in survival in both communities (χ2, P Odocoleus virginianus).

The origins and implications of paleochannels in hyperarid, tectonically active regions: The northern Atacama Desert, Chile

Preserved remnants of fluvial activity in deserts constitute evidence for changing boundary conditions. The Atacama Desert of northern Chile is the global end-member for aridity, so the history of relict stream networks in this region is a record of how landscapes develop under extreme conditions. On Pampa de Tana in northern Chile (19.4°S), a series of channel forms that are presently inactive but in the past flowed westward are incised into the surface of a fault bounded, topographically elevated portion of the El Diablo Formation, a regionally extensive, relict pediment. We measure cosmic-ray produced 10Be, 26Al and 21Ne in fluvial deposits to date the timing of abandonment of three channels and couple this with topographic profile information from a SPOT-6 derived, 2 m resolution digital elevation model. We find two of the channels were abandoned approximately >5.6 Myr and 2.0 Myr ago. One channel is still capable of flow and has ages suggesting it was fluvially active within the last few hundred thousand years. Using the paleochannel ages measured here and published ages for the end of aggradation of the El Diablo Formation we estimate the rates of fluvial channel incision before channel abandonment, and uplift rates on the faults after channel abandonment. Maximum uplift rates of ~12 m/Myr over the last 2 Myr are found. In general, while rates of uplift are relatively low they are several-fold more rapid than the rates of fluvial incision prior to channel abandonment. This implies that westward channel flow was interrupted by uplift of topography above a blind NW-SE striking reverse fault that affects the Central Depression, an alluvial forearc basin. We consider also that shrinkage of the upstream catchment area by stream capture, promoted via headward erosion and lateral expansion of adjacent canyons (quebradas) could be a factor in the abandonment of the channels on Pampa de Tana. Our results highlight the polygenetic nature of this landscape and show that relatively minor amounts of fault displacement in hyperarid regions can have implications for stream network evolution. Even subtle topographic uplift upstream should be taken into account when fluvial deposits are used as proxies for long-term environmental conditions.

Use of Wyoming Southern Bighorn Mountains Topographic Map Evidence to Test a Recently Proposed Regional Geomorphology Paradigm: USA

Detailed topographic maps covering a high elevation Bighorn-Powder River drainage divide segment in the southern Bighorn Mountains are used to test a recently proposed regional geomorphology paradigm. Fundamentally different from the commonly accepted paradigm the new paradigm predicts immense south-oriented continental ice sheet melt water floods once flowed across what is now the entire Missouri River drainage basin, in which the high Bighorn Mountains are located. Such a possibility is incompatible with commonly accepted paradigm expectations and previous investigators have interpreted Bighorn Mountains geomorphic history quite differently. The paradigm test began in the high glaciated Bighorn Mountains core area where numerous passes, or divide crossings, indicate multiple and sometimes closely spaced streams of water once flowed across what is now the Bighorn-Powder River drainage divide. To the south of the glaciated area, but still in a Precambrian bedrock region, the test found the roughly adjacent and parallel south-oriented North Fork Powder River and Canyon Creek headwaters located on opposite sides of the Bighorn-Powder River drainage divide with North Fork Powder River headwaters closely linked to a 300-meter deep pass through which south-oriented water had probably flowed. Shallower divide crossings located further to the south suggest diverging and converging streams of water once flowed not only across the Bighorn-Powder River drainage divide, but also across Powder River and Bighorn River tributary drainage divides. The paradigm test also found published geologic maps and reports showing the presence of possible flood transported and deposited alluvium. While unable to determine the water source, the new paradigm test did find evidence that large south-oriented floods had crossed what was probably a rising Bighorn Mountains mountain range.

Deep-sea mobile megafauna of Mediterranean submarine canyons and open slopes: Analysis of spatial and bathymetric gradients

Mediterranean canyons are generally characterized by complex topography and hydrographic conditions, and can act as conduits for organic matter and sediments from the shelf to the deep sea, which result in enhanced macro- and megafaunal abundance and biodiversity. Here, we reviewed the literature of the last 20 years and combined available information with new data, from our own datasets (including unpublished data), on megafaunal species inhabiting submarine canyons and the adjacent slopes. We analysed the data acquired using different gears, from baited cameras on aluminum frames and landers and baited traps to commercial trawl gears, in order to combine and complement the results in megafaunal biodiversity and assemblage structure in Mediterranean canyons. Overall, the results of our analysis on megafaunal assemblages allowed identifying 400 species, including 28 species of cephalopods, 64 of decapod crustaceans, 25 of echinoderms, 27 of elasmobranches and 127 of Actinopterygii. We observed significant longitudinal differences in assemblage composition, with high species turnover across Mediterranean sub-basins. Our analysis also confirmed the importance of depth axis as the main factor influencing the structure of the deep-sea demersal assemblages, with greater diversity in the upper part of the slopes. The multivariate multiple regression analysis showed that geomorphological features of the canyons (i.e., slope, dendricity, sinuosity, and distance from adjacent canyons) contribute significantly to explain the observed variability in the taxonomic composition of megafaunal assemblages at sub-basin scale. The results presented here are important in global biodiversity management perspectives, and confirm that canyons represent a seascape unit deserving protection at different levels modulated according to biogeographic and geomorphological features.

Cold-Water Coral Habitats in Submarine Canyons of the Bay of Biscay

The topographical and hydrological complexity of submarine canyons, coupled with high substratum heterogeneity, make them ideal environments for cold-water coral (CWC) habitats. These habitats, including reefs, are thought to provide important functions for many organisms. The canyons incising the continental slope of the Bay of Biscay have distinct morphological differences from the north to the south. CWCs have been reported from this basin in the late 19th century; however, little is known about their present-day distribution, diversity and environmental drivers in the canyons. In this study, the characteristics and distribution of CWC habitats in the submarine canyons of the Bay of Biscay are investigated. Twenty-four canyons and three locations between adjacent canyons were sampled using a Remotely Operated Vehicle (ROV) or a towed camera system. Acquired images were annotated for habitat type (using the CoralFISH classification system), substrate cover and coral identification. Furthermore, the influence of hydrological factors and geomorphology on the CWC distribution was investigated. Eleven coral habitats, formed by 62 morphotypes of scleractinians, gorgonians, antipatharians and seapens, inhabiting hard and/or soft substrate, were observed. The distribution patterns were heterogenous at regional and local scales; the south Bay of Biscay and the southeastern flank favored soft substrate habitats. Biogenic and hard substrate habitats supported higher coral diversities than soft substrate habitats and had similar species compositions. A higher coral species turnover characterized soft substrate habitats. Substrate type was the most important driver of the patterns in both distribution and composition. Observations of coral reefs on steeper areas in the canyons and coral rubble on flatter areas on the interfluve/upper slope, support the hypothesis that canyons serve as refuges, being less accessible to trawling, although natural causes may also contribute to the explanation of this distribution pattern. The results of this study fed into a proposal of a Natura 2000 network in the Bay of Biscay where management plans are rare.

A decision support tool for evaluating the air quality and wind comfort induced by different opening configurations for buildings in canyons

This study formulated a new index for evaluating both the air quality and wind comfort induced by building openings at the pedestrian level of street canyons. The air pollutant concentrations and wind velocities induced by building openings were predicted by a series of CFD simulations using ANSYS Fluent software based on standard k-ɛ model. The types of opening configurations investigated inside isolated and non-isolated canyons included separations, voids and permeable elements. It was found that openings with permeability values of 10% were adequate for improving the air quality and wind comfort conditions for pedestrians after considering the reduction in development floor areas. Openings were effective in improving the air quality in isolated canyons and different types of opening configurations were suggested for different street aspect ratios. On the contrary, openings were not always found effective for non-isolated canyons if there were pollutant sources in adjacent street canyons. As such, it would also be recommended introducing openings to adjacent canyons along with openings to the target canyons. The formulated index can help city planners and building designers to strike an optimal balance between air quality and wind comfort for pedestrians when designing and planning buildings inside urban streets and thus promoting urban environmental sustainability.

Potential impacts to perennial springs from tar sand mining, processing, and disposal on the Tavaputs Plateau, Utah, USA

Similar to fracking, the development of tar sand mining in the U.S. has moved faster than understanding of potential water quality impacts. Potential water quality impacts of tar sand mining, processing, and disposal to springs in canyons incised approximately 200m into the Tavaputs Plateau, at the Uinta Basin southern rim, Utah, USA, were evaluated by hydrogeochemical sampling to determine potential sources of recharge, and chemical thermodynamic estimations to determine potential changes in transfer of bitumen compounds to water. Because the ridgetops in an area of the Tavaputs Plateau named PR Spring are starting to be developed for their tar sand resource, there is concern for potential hydrologic connection between these ridgetops and perennial springs in adjacent canyons on which depend ranching families, livestock, wildlife and recreationalists. Samples were collected from perennial springs to examine possible progression with elevation of parameters such as temperature, specific conductance, pH, dissolved oxygen, isotopic tracers of phase change, water-rock interaction, and age since recharge. The groundwater age dates indicate that the springs are recharged locally. The progression of hydrogeochemical parameters with elevation, in combination with the relatively short groundwater residence times, indicate that the recharge zone for these springs includes the surrounding ridges, and thereby suggests a hydrologic connection between the mining, processing, disposal area and the springs. Estimations based on chemical thermodynamic approaches indicate that bitumen compounds will have greatly enhanced solubility in water that comes into contact with the residual bitumen–solvent mixture in disposed tailings relative to water that currently comes into contact with natural tar.

MODELING THE COAST DYNAMICS OF THE IMERETINSKAYA LOWLAND

It is shown that the coastline near the canyon Novyi is characterized by a rapid recession (about 7 m/y). Simultaneously the coast prominence at Cape Konstantinovskiy is truncated (4 m/y), and the eroded material is mainly transported into adjacent canyons. At the east ledges of the canyons Novyi and Konstantinivskiy the wave refraction leads to the energy concentration and the increase of longshore drift capacity. Because of intensive incision the drift of deposits will after some time run out. In order to save the beaches a pebble material should be placed into eroded coast sections (90 and 50 m 3 m -1 y -1 , respectively).

The wind in the hollows

Flowing water shapes most of Earth's canyons, obscuring the contributions of other erosional mechanisms. A comparison of adjacent canyons with and without wind shielding shows that wind can amplify canyon incision on windblown Earth and Mars.

A Porites lutea climate record from Sodwana Bay, South Africa

We report on a 41-year (winter 1970 to winter 2010) Porites lutea coral core climate record from Two-Mile Reef, Sodwana Bay, in the South-Western Indian Ocean. X-ray analysis, ultraviolet fluorescent photography and stable isotope (δ18O and δ13C) analysis revealed skeletal high-density, late-winter and low-density, late-summer bands with very little terrestrial humic input. An overall decrease in coral growth rate was seen over this period, possibly linked to global temperature and acidification trends. The stable isotopes δ18O and δ13C were predominantly out of phase, with calculated temperatures showing a slight increase over the 41-year period but with an overall decrease from 1994 to 2010. The insignificant ocean warming recorded in the coral supports the existence of a local, self-regulating, cold-water upwelling system from the adjacent shelf break and canyons that is potentially moderating coastal water temperature rise in Sodwana Bay.

Mitochondrial phylogeography of the endangered blunt-nosed leopard lizard,Gambelia sila

To assess the genetic diversity and phylogeography of the blunt-nosed leopard lizard (Gambelia sila), we sequenced 1,285 base pairs (bp) of the mitochondrial cytochrome oxidase-b (cyt-b, 682 bp) and cytochrome oxidase III (CO3, 603 bp) genes from 33 individuals representing eight natural populations in central California. Phylogenetic analysis indicated that 17 observed haplotypes are partitioned into two major clades, which correspond geographically to where the lizards were collected. We also conducted a focused analysis of individuals collected from the canyons leading into the Cuyama Valley in Ventura and Santa Barbara counties, a geographic area with lizards possibly representing a remnant hybrid (with G. wislizenii) population. All lizards from the Cuyama Valley and adjacent canyons exhibited the mitochondrial haplotype of G. sila and were embedded within one clade. Our morphological analysis placed some leopard lizards collected from Cuyama Valley with true G. sila, whereas some individuals aggregated with G. wislizenii. This finding suggests that the quantitative morphological characteristics often used to distinguish between the two species are fairly labile and may be influenced by prevailing environmental conditions.