The ongoing global Climate Crisis has sparked a strong interest in climate reconstructions and models of geological periods with high atmospheric CO2 concentrations.
But how much do we really now about the dynamics of Earth’s past climate and coastal ecosystems on the human timescale?
Now that concern is rapidly rising about the catastrophic effect of extreme weather events and seasonality, especially to our sensitive and economically important coastal areas, biogenic carbonate producers like mollusks (clams and snails) rise to the occasion as ideal archives for environmental and ecosystem change at the timescale that matters: days to decades.
In this talk, I will try to answer the question: What can these beautifully preserved shells teach us about the occurrence of extreme weather and seasonality under various climate states?
Tropical climates, such as SE Asia, can lead to poor exposure and heavily weathered outcrops. Whilst fieldwork can give an important insight into the underlying geology, detailed detrital analysis is essential to fill in the gaps. Here, a combination of light minerals, heavy minerals, and detrital grain ages from around SE Asia are used to try to reconstruct palaeogeographies in an area of complex tectonics.
Submarine landslides are gravity-driven mass movements that occur in underwater slope settings worldwide. Despite their potential to damage expensive seafloor infrastructure such as pipelines or telecommunication cables and to generate hazardous tsunamis, many aspects of submarine landslide formation remain poorly understood. Many studies have proposed that the formation of submarine landslides on seemingly stable slopes may be explained by weak layers within the slope stratigraphy. Our understanding of weak layers, especially their compositional and structural characteristics, however, is restricted due to often limited data availability and resolution. This talk will focus on the integration of datasets at different scales and resolution in order to both qualitatively and quantitatively investigate the role of sediment structure and composition on weak layer and submarine landslide formation.
Investigations in living microbialites are providing significant data that are critical to disentangle the role of the various biotic and abiotic processes contributing to their development. Despite these efforts separating the impact and magnitude of these processes remain a difficult task.
Field and laboratory studies in modern lacustrine environments from the Andes to the Alps show that extrinsic – environmental – factors might have a changeable impact over short periods of time switching mineral precipitation from biotic to abiotic and vice-versa. Such switch may or may not be distinguishable in fossilized microbialites.
Global marine archives from the early Pleistocene suggest that glacial-interglacial cycles, and their corresponding sea-level cycles, have predominantly a periodicity of ~ 41 kyrs driven by Earth’s obliquity. However, in Taiwan, clastic shallow-marine strata from the early Pleistocene challenge the idea of a “41-kyr world”. The studied strata revealed precession-dominated sea-level fluctuations during the early Pleistocene, independent of a global ice-volume proxy. Preservation of this signal is possible due to the high-accommodation creation and high-sedimentation rate in the basin, enhancing the completeness of the stratigraphic record.
Macrofossils have the potential to provide significant sedimentological data, from aiding the interpretation of depositional settings, understanding the processes operating to concentrate fossils, palaeocurrent interpretation, to diagenetic analysis and much more. Join us to learn more about how to leverage your lamellibranchs, exploit your echinoids and generally put your palaeo to work.
Investigations of tsunami sedimentology has expanded dramatically in recent years following the devasting ‘Boxing Day’ Indian Ocean Tsunami in 2004. Tsunamis cause significant coastal erosion and can deposit sand sheets on coastal plains. In this talk we demonstrate the potential to trace tsunami sands and associated erosional scours in the shallow subsurface using ground-penetrating radar (GPR). We will include examples form the 2004 Indian Ocean Tsunami in Thailand and Indonesia as well as the Storegga tsunamis in Scotland and the Shetland Islands.
Seds Online Student Webinar (SOSW 4): Exploring sediment transport dynamics from source to sink
Presenters: Nikhil Sharma (University of Geneva), Octria Prasojo (University of Glasgow) Jing Lyu (University of Bremen) Maximilian Droellner (Curtin University)
The carbonate factories model, as defined at the beginning of this century, provides a subdivision of marine carbonate sediment production-systems based on the style of carbonate precipitation. The main factors controlling marine carbonate precipitation are light, water temperature, nutrients, salinity, substrate and carbonate saturation. Site-specific controls influencing the systems comprise ocean currents, upwelling and non-upwelling systems, ocean-atmosphere systems, atmospheric systems, shallow-water dynamics, and terrestrial sediment and water input.
The sequence stratigraphic patterns differ for the individual factories. The Tropical factory being light dependent is characterized by higher sediment production when the platform tops are flooded (highstand shedding). It displays decoupled sediment wedges with the partial infill of accommodation in the shallow-water realm and major sediment export towards the slopes and surrounding basins. The Cold-Water Coral factory is marked by in situ production and deposition with limited sediment export forming single cold-water coral spots or sediment accumulation ridges. The Cool-Water factory has a siliciclastic equivalent style of sediment distribution with lowstand-dominated, shelf edge wedges and a shaved-off shelf during sea-level highstands. Slope shedding marks the Microbial factory in which sediment production occurs within the upper slope realm of the flat-topped platforms both during highstands and lowstands in sea-level. This allows for fairly continuous sediment production exhibiting minor impact of sea-level changes, but with progradation, aggradation, and retrogradation of the system being only limited by local environmental changes. Planktic factory sediment production may vary in accordance with variations in sea-level providing time lines, systems tracts boundaries, in the pelagic realm.
In summary, each factory is branded by an individual set of features, e.g. production window, sediment production and export, morphologies and slopes. It is this unique set of variables marking each factory that determines the factory-dependent response to small-scale and large-scale environmental changes through space and time as shown in the sequence stratigraphic development.
Humans are becoming increasingly active and increasingly recognized as geomorphic agents, and a key value of Earth surface processes research is its relevance to society. As 21st century landscapes evolve at unprecedented rates, knowledge of human-landscape interactions is needed to design effective management strategies for sedimentary basins. In this talk, I present findings from sediment dating and archaeological investigations in the Mississippi Delta, USA, a delta that has experienced rapid land loss over the past century. I use these results to describe the relationship of prehistoric settlement patterns to delta evolution and offer insights into prehistoric, contemporary, and future human-landscape interactions in the Mississippi Delta and other coastal sedimentary basins.
Brine, with salinities reaching six times that of seawater, occurs as groundwater throughout the subsurface of the McMurdo Dry Valleys and the Victoria Land Basin, Antarctica. This brine, derived from seawater freezing, is responsible for widespread precipitation of calcite, dolomite and aragonite cement and alteration of skeletal grains in Cenozoic glaciomarine strata. Relationships among depth, sediment age, and cement precipitation temperature suggest that cement—and brine—likely formed during discrete periods of cooling and ice sheet expansion.
Viruses are very much in the news these days, unfortunately, but what about their geological history? Are viruses preserved in the fossil record, considering they are so small and you cant even see them ? If they are, how does that happen and how far back do they go? And what about the roles of viruses in the environment? Are they significant or were they just the nasty invisible parasites we regard them to be today, disrupting life as we know it ? Or are they both – good and bad?
Seds Online Great Debate
Topic: Autogenic Processes in Sedimentary Systems are Just Part of the allogenic spectrum
Arguing for the motion: Andre Strasser (Université de Fribourg), David De Vleeschouwer (University of Bremen)
Arguing against the motion: Sam Purkis (University of Miami), Anthony Shillito (Oxford University)
Tidal meandering channels are ubiquitous features of coastal landscapes. Their migration produces point-bar deposits characterized by inclined heterolithic stratification, fining-upward vertical trends, abundance of fine-grained sediments, and tidal rhythmites. Although these criteria are widely accepted, facies models for tidal point bars still lack a 3D perspective and overlook the along-bend variability of sedimentary processes. In this seminar, we will focus on a hypertidal point bar belonging to the upper-intertidal domain of the Mont-Saint-Michel Bay (France), and we will look at the sedimentology of a 3D time-framed accretionary package formed between 28/03/2012 and 29/11/2012. Integration between Lidar topographic time-series data, geomorphological field surveys and sedimentary-core data shows that over this time the bar expanded alternating depositional phases along its seaward and landward sides. The maximum thickness of deposits was accumulated in the bar apex zone, and just landward of it, where the largest amount of mud was also stored. High accretion rate of the bar apex zone endorsed also a better preservation of tidal rhythmites, which are almost missing from deposits accumulated along the bar sides (i.e. close to riffles). We suggest that alternating depositional loci and high sediment accretion at the bend apex zone emerge due to a combination of factors, including: i) the spatio-temporal asymmetric nature of tidal currents, which influenced deposition and preservation of flood and ebb deposits along the bend; and ii) the development of low-energy conditions at the apex due to ebb and flood flow configuration, which also promoted mud settling.
Ground-penetrating radar (GPR) is commonly used in the search for buried infrastructure but can also be used for local correlation, sand-body geometry, and sedimentary architecture. It provides a high-resolution image of shallow stratigraphy and can be widely applied in sedimentology. This talk will focus on sedimentary applications including examples from a range of different sedimentary environments including rivers, beaches, sand dunes and peat bogs.
Seds Online Student Webinar (SOSW 3): New insights into coastal processes from the sedimentological record
Liz Mahon (University of Melbourne)
Yannis Kappelmann (University of Bremen/Leibniz Centre for Tropical Marine Research)
Laura Buhrig (University of Leeds)
Kat Wilson (The University of Texas at Austin)
While ever-improving analytical techniques and the ability to absolute date diagenetic phases are driving ever more sophisticated interpretations in carbonate sedimentology, observation-based studies have also led to huge shifts in how we perceive carbonate diagenesis. We now appreciate, but have yet to fully understand, how critically important mineral transformations and translocations in marine fluids are during even very shallow burial. What controls diagenesis in shallow meteoric systems is also being revised, and there is a rapidly growing appreciation of the extent of how hypogene fluids have the ability to modify limestones even at the seismic-scale. Thus the framework in which we interpret marine, meteoric and burial carbonate diagenesis has been, and still is, undergoing a series of paradigm shifts.
Most tidal channels in both estuarine and lagoonal environments have a tendency to meander, yet very few studies have analyzed their morphometric characteristics and morphodynamic evolution. In spite of recent breakthroughs in numerical, experimental, and field techniques, an investigation on the full spectrum of the processes controlling tidal-meander evolution remains challenging. The Venice Lagoon (Italy) offers a unique opportunity to shed light on this topic, because a long record of morphological and sedimentary data is available, which allows one to relate tidal channel evolution to the hydrodynamic and morphological changes undergone by the lagoon. In particular, during the last 130 years, feedbacks between rising relative sea levels and anthropogenic interventions have caused severe modifications of the hydrodynamics and morphology of the Lagoon. Here we investigate how these modifications fed back into the morphodynamic evolution of a meandering tidal channel located in the northern Lagoon. Combining extensive datasets of aerial photographs, topographic and bathymetric survey, geophysical investigations, sedimentary core analysis, and numerical modeling, we illustrate how changes in local hydrodynamics determined the evolution of the study channel by inducing adjustments of both its cross-sectional areas and bed morphologies, thereby ultimately impacting meander planform dynamics. We also discuss how alterations in sediment transport regime affected tidal point-bar sedimentology, and suggest that wave-enhanced concentrations of suspended sediment during slack water conditions could have hampered the formation of high-relief bedforms.