Paleoenvironment Implication of Red Paleosols in a Late Cretaceous Continental Succession, Songliao Basin, NE China

The limited knowledge of Late Cretaceous terrestrial environments and their response to tectonic events in mid-latitudes can be addressed through continental basin deposits such as paleosols. Paleosols have been discovered in the Late Cretaceous Yaojia Formation in the southern Songlaio Basin and are recognized by evidence of soil structures controlled by pedogenesis. Sedimentary facies research on red paleosols was conducted on the Late Cretaceous Yaojia Formation in the outcrop of the southern Songliao Basin to interpret the depositional environments and tectonic significance of red paleosols during the greenhouse period. Mudflat, lake margin, and shallow lake depositional environments in a semi-arid climate are interpreted from the outcrops based on sedimentary descriptions and interpretation as well as geochemical and micromorphological analyses of paleosols in outcrops. We reconstructed the paleoenvironmental and paleoclimatic conditions through the paleosols in the mudflats and lake margin. The red paleosols in the mudflats and lake margin deposits formed in a stable landscape influenced by the tectonic uplift of the Songliao Basin, which is considered as new important evidence for tectonic uplift influenced by the collision of the Okhotomorsk Block with East Asia. The tectonic uplift process in East Asia is identified from the evolution of the depositional environments and drainage conditions inferred from different types of paleosols. Thus, the paleosols-bearing red bed deposits in outcrops provide an important contribution of the Late Cretaceous terrestrial paleoclimate and the tectonic setting research.

Depositional system and lake-stage control on microbialite morphology, Green River Formation, eastern Uinta Basin, Colorado and Utah, U.S.A.

ABSTRACT Lake-margin lacustrine carbonates of the Green River Formation, in the eastern Uinta basin of Colorado and Utah, occur interbedded with fluvial and shoreline-parallel sandstone and shale. Microbial bindstones were deposited in a saline-alkaline lake during and after the Early Eocene Climate Optimum (EECO) (52–50 million years ago) that is characterized by global hot-house conditions, elevated atmospheric CO2, and highly fluctuating climate conditions. The stratigraphic architecture, chemostratigraphy, and morphology of the microbialites and other associated carbonate beds can be related to these climatic conditions. Three facies associations are recognized in the carbonate units across the lake margin from upper littoral to lower sublittoral environments: facies association 1, delta proximal non-microbial carbonates, characterized by quartzose bioclastic, peloidal, intraclastic packstones and grainstones–rudstones, quartose peloid wackestones and sandy oil shale; facies association 2, microbialite associated non-microbial carbonates, composed of ostracod, ooilitic, peloidal packstones–grainstones and intraclastic packstones, grainstones and rudstones; and facies association 3, microbial carbonates, consisting of diverse forms of stromatolitic and thrombolitic lithofacies. Multiple scales of carbonate cyclicity are suggested by shifts of δ18O and δ13C stable isotopes and deepening-upward microbialite facies. High-frequency cycles, on the order of 1 to 5 m thickness, are characterized by positive shifts in stable isotopes and interpreted deepening trends from littoral to lower sublittoral conditions. Large-scale trends, on the order of tens to hundreds of meters thickness record long-term lake changes, including: 1) sparse microbialite deposition during initial fresh conditions in lake stage 1, with low macro-structure diversity and light δ18O and δ13C isotope values; 2) transitional lake stage 2 corresponding to moderate macro-structural diversity, large meter-scale biostromal and biohermal buildups, and a positive shift in δ18O and δ13C isotope values that suggest increasing saline and alkaline conditions; 3) a highly fluctuating lake stage 3 that contains the highest microbialite macro-structural diversity and marks the interval of heaviest δ18O and δ13C isotope values, suggesting the greatest lake restriction, and the highest salinity and alkalinity conditions; and 4) a rising lake stage 4 that marks the lowest microbialite macro-structure diversity and a reversal in trend of δ18O and δ13C isotope values, that indicate deepening and freshening conditions.

Iceberg dynamics in a proglacial lake in Austria quantified by time-lapse photography

<p>The recession of glaciers reveals a dynamic landscape exposed to high rates of hydrological and geomorphological modifications. Such deglaciation processes caused the formation of a 0.3 km² large proglacial lake (named Pasterzensee) near the terminus of Pasterze Glacier, Austria, during the last two decades. The evolution of the proglacial lake was accompanied by several buoyant calving events. The process of buoyant calving formed numerous floating dead ice bodies referred to as icebergs which covered a maximum of 7.3 % of the entire proglacial lake basin in November 2018.</p><p>Despite the existence of icebergs at some proglacial lakes in the European Alps, little is known about the evolution and life span of icebergs in proglacial lakes in the European Alps. The aim of this study was to reduce this research gap by (a) quantifying the evolution of such alpine icebergs during two different time scales and by (b) analysing the relationship between iceberg evolution and motion at the lake with meteorological conditions. At a long-term scale, one single iceberg was monitored during the period 01.09.2017-30.09.2019. At a short-term scale, all icebergs were studied during one single day (16.06.2019).</p><p>The most important data source for this study were time-lapse optical imagery from an automatic camera overlooking the entire proglacial lake (GROHAG). The used camera is a Roundshot Livecam Generation 2 (Seitz, Switzerland). Photographic imagery is captured every five minutes (during daylight) from a location 310 m above lake level and 450 m northeast of the lake margin. For the long-term analysis, a total number of 386 pictures of the lake were processed. For the short-term analysis, 97 pictures were analysed to reveal the dynamics of 84 icebergs during one single day. The oblique time-lapse images were transformed into orthorectified photos using a rectification algorithm which considers the camera properties and the lake surface geometry. Iceberg size and centroid coordinates were mapped in all generated orthophotos. In addition, meteorological data (ZAMG Vienna) was provided by a nearby automatic weather station, located at the glacier tongue of Pasterze Glacier some 1.1 km northwest of the lake margin.</p><p>Results indicate that the monitoring of one iceberg over a period of 25 months revealed highest melting rates from June to August, low melting rates from September to November and no measurable melting when the lake surface is frozen. Horizontal iceberg displacement is rising with decreasing iceberg size throughout the study period. The analysed iceberg formed during the detachment of a debris covered ice peninsula with an initial size of 7250 m² and was last identifiable at a size of 240 m². Monitoring lake-wide iceberg movement for one day shows that wind is the main influence on horizontal iceberg displacement. The existence of a strong valley wind, caused by a diurnal warming cycle, is observed. This wind system decouples the iceberg movement from the constant katabatic glacier wind, recorded by the weather station. Frequent jumps in movement rates, which are not explained by wind data, suggest that iceberg grounding is a common process influencing subaquatic lake morphology.</p>

Taphonomic information from the modern vertebrate death assemblage of Doñana National Park, Spain

Modern death assemblages provide insights about the early stages of fossilization and useful ecological information about the species inhabiting the ecosystem. We present the results of taphonomic monitoring of modern vertebrate carcasses and bones from Doñana National Park, a Mediterranean coastal ecosystem in Andalusia, Spain. Ten different habitats were surveyed. Half of them occur in active depositional environments (marshland, lake margin, river margin, beach and dunes). Most of the skeletal remains belong to land mammals larger than 5 kg in body weight (mainly wild and feral ungulates). Overall, the Doñana bone assemblage shows good preservation with little damage to the bones, partly as a consequence of the low predator pressure on large vertebrates. Assemblages from active depositional habitats differ significantly from other habitats in terms of the higher incidence of breakage and chewing marks on bones in the latter, which result from scavenging, mainly by wild boar and red fox. The lake-margin and river-margin death assemblages have high concentrations of well preserved bones that are undergoing burial and offer the greatest potential to produce fossil assemblages. The spatial distribution of species in the Doñana death assemblage generally reflects the preferred habitats of the species in life. Meadows seem to be a preferred winter habitat for male deer, given the high number of shed antlers recorded there. This study is further proof that taphonomy can provide powerful insights to better understand the ecology of modern species and to infer past and future scenarios for the fossil record.

Formação de ondas e os processos erosivos nas margens do lago da UHE Xingó

As características dos ventos têm uma grande influência no modo como as ondas são geradas, se propagam e promovem erosão nas margens de rios e lagos. Entre essas características, a velocidade e a direção do vento assumem um papel crucial, influenciando os principais parâmetros que caracterizam as ondas, designadamente a altura de onda e o período (tempo de duração). Esse trabalho teve como objetivo caracterizar a geração de ondas no Lago da UHE Xingó e as consequências nos processos erosivos na sua margem. Foram levantados dados in situ e das fontes disponíveis no SIMA - Sistema Integrado de Monitoração Ambiental. A coleta de dados de vento in loco foi realizada a partir da utilização de um anemômetro instalado em períodos determinados, em pontos diferentes da margem do lago, para que permitisse a comparação com os dados pretéritos coletados pelo SIMA. Os focos de erosão reconhecidos na extensão das pistas de vento, foram georeferenciados sendo realizada a sua associação com a direção dominante dos ventos, que promovem a consequente formação de ondas. Percebeu-se ventos diurnos maiores que os noturnos nos períodos mais secos, e também o desenvolvimento de ondas acompanhando essa tendência, ou seja, menores à noite do que no dia. Foram identificados 8 (oito) fetchs representativos dos ventos dominantes no Lago da UHE Xingó, todos com forte relação com os focos de erosão identificados, e percebeu-se pouca variação nos valores máximos de ondas em todas as pistas de vento, não ultrapassando o valor de 0,16m, ocorrente no período diurno. Wave formation and erosive processes in the margins of Lake XingóA B S T R A C TThe characteristics of the winds have a great influence in the way the waves are generated, they propagate and they promote erosion in the riverbanks and lakes. Among these characteristics, wind speed and direction play an important role, influencing the main parameters that characterize waves, namely wave height and period (duration time). The objective of this work was to characterize the generation of waves in the Xingó Power Dam and the consequences on the erosive processes. Data were collected in situ and compiled from the available sources in the SIMA - Integrated Environmental Monitoring System. Wind data collection was carried out using an anemometer installed at specific periods of the year, at different points in the lake margin, to allow the comparison with previous data collected by SIMA. The erosion recognized in the extension of the fetchs were georeferenced, and their association with the dominant direction of the winds was carried out, which promote the consequent formation of waves. Higher daytime winds were observed than the nocturnal ones in drier periods, and also the development of waves accompanying this trend, that is, smaller at night than in the daytime. Eight (8) representative fetchs of the prevailing winds in the Xingó Power Dam were identified, all of them strongly related to the identified erosion spots, and with few variation in the maximum wave heights values for all identified values not exceeding the value of 0.16m and in the daytime period.Keywords: Wind speed, fetch; São Francisco River; erosion.

Holocene palaeoenvironmental records from the high-altitude Wular Lake, Western Himalayas

We present a comprehensive record of Holocene (11,590–628 cal. yr BP) climate and hydrographic changes around the Wular Lake located in Kashmir Valley, India. Based on the multi-proxy investigations, we have identified three phases of wet climate conditions that prevailed from the commencement of the Holocene Epoch – 9000 cal. yr BP, 8100–6650 cal. yr BP and 6350–5000 cal. yr BP, whereas periods of dry climate were observed during 9000–8100 cal. yr BP, 6650–6350 cal. yr BP and ~5000 to 4000 cal. yr BP. The results also suggested that the lake widened and deepened significantly around 6350–5000 cal. yr BP. The results indicated desiccation and the exposure of the lake margin around 5000–4500 cal. yr BP. The sedimentation rate since 4500–628 cal. yr BP was quite low for detailed paleoclimate interpretations. Oscillations in lake extension and deepening appear to be due to changing intensity of westerly moisture in the region, and we correlate several of the low lake-level phases to the Bond events caused by North Atlantic ice rafting events.

A note regarding conditioning simulation trials for data-poor management strategy evaluations

A boat-based survey was conducted in the Tefé river and lake (Brazil) in December 2013, during the transitional water period. A combination ofstrip-width transects parallel to the river, lake-margins and confluences, and cross-channel line transects in the lake, were used to cover a totaldistance of 670 linear kilometres of the dolphins’ habitat. A total of 383 groups of Amazon river dolphin and 124 groups of tucuxi were observed.Group size, density and abundance estimates were obtained per species and habitat (tributary, lake-margin and confluence). Group sizes rangedfrom one to six individuals for the Amazon river dolphin and from one to eight individuals for the tucuxi. The abundance of river dolphins washigher for the Amazon river dolphin (911, CV = 0.15) than the tucuxi (511, CV = 0.26). Higher densities were found in the lake-margin and tributaryfor the Amazon river dolphin and in the confluences for the tucuxi. Lake-margins, confluences and tributaries are therefore proposed as criticalhabitats for the conservation of river dolphins in central Amazonia. The Tefé lake is identified as an area of concern due to a high number of humanstressors such as boat traffic, fishing and habitat degradation.