Scientific Webinars

Marine Carbonate Factories: Sedimentation Patterns and Sequence Stratigraphy

John Reijmer - Vrije Universiteit Amsterdam

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.

A geoarchaeological perspective on the challenges and trajectories of Mississippi Delta communities

Elizabeth Chamberlain - Wageningen University

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.

Salty tales of diagenesis in Antarctica

Tracy Frank - University of Connecticut

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 in carbonate precipitation ? the new frontier in Earth Sciences ?

Maurice Tucker - University of Bristol

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: Autogenic Processes in Sedimentary Systems are Just Part of the allogenic spectrum

Andre Strasser, David De Vleeschouwer, Sam Purkis, Anthony Shillito

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)

3D architecture and along-bend sediment distribution of a hypertidal point bar (Mont-Saint-Michel Bay, France)

Marta Cosma - "National Research Council of Italy - CNR Institute of Geosciences and Earth Resources – IGG"

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.

GPR Applications in Sedimentology

Charlie Bristow - Birkbeck University of London

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.

Carbonate diagenesis is now much more interesting than it used to be: I’ll prove it

Paul Wright - National Museum Wales & PW Carbonate Geoscience

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.

130 years of natural and anthropogenic modifications of the Venice lagoon unravel morpho-sedimentary evolution of tidal meanders

Alvise Finotello - University of Venice

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.

Roles of oceanography and orbital forcing in greenhouse climates

Sietske Batenburg - University of Barcelona

In climates that were warmer than at present, orbital parameters exerted a strong control on environmental conditions, which often resulted in the deposition of rhythmic sedimentary sequences. Especially in the marine realm, such successions reveal the pacing of past climates and can provide detailed time scales for climate perturbations. Ocean circulation played a major role in greenhouse climates by distributing heat and nutrients. I aim to disentangle the role of geography, for example through the opening of gateways, from the role of a warmer climate on the behaviour of ocean currents.

Discontinuity in equilibrium wave–current ripple dimensions on mixed clay-sand substrates

Xuxu Wu - University of Hull

We conducted a large-scale flume experiment to investigate combined-flow ripple development on mixed sand-clay beds. The experiment results reveal a threshold bed clay content controlling the generation of two distinct types of equilibrium ripples: large ripples are comparable with clean-sand counterparts and relatively small and flat ripples reflect strong bed cohesion preventing ripple growth. Additionally, we find clay loss at relatively deeper layer below the large equilibrium ripples due to strong clay winnowing under combined flow. This possibly reduces rippled bed stability.

Disentangling the controls and orbital pacing of South-East Atlantic carbonate deposition since the Oligocene (30-0 Ma)

Anna Joy Drury - University College London

In this study we use XRF core scanning to approximate carbonate content at Wallis Ridge in the Southeast Atlantic. We then look at how the patterns of carbonate deposition in this region have changed over the last 30 million years, and see what this record can tell us about how climate, the cryosphere and the carbon cycle interacted since the early Oligocene.

Submarine channel-lobe transition zones in an ancient passive-margin turbidite system

Lilian Navarro - Cape Breton University, University of Ottawa

Deep-water turbidite systems have been the focus of much research during several decades, particularly much work has been done on slope channels and associated levees and basin-floor depositional lobes, but with much less attention devoted to the channel to lobe transition zone (also known as CLTZ) that separates them. Based on detailed lithological and architectural analyses of an interval consisting of intercalated, sheet-like, sandstone-rich strata that transition upward to channelized sandstones bounded by mudstone-rich strata of the Neoproterozoic, passive-margin Windermere turbidite system in the southern Canadian Cordillera, this study provide new insights into the spatial and temporal development of an ancient channel-lobe system and its related CLTZ (s), which are here interpreted to be largely linked to major changes in sediment supply and related flow characteristics (such as flow efficiency, and bypassing versus depositional character).

Linking morphodynamics of deltaic distributary networks to stratigraphic connectivity of channel bodies

Elisabeth Steel - Queen’s University

In deltaic environments, distributary channel networks serve as the primary conduits for water and sediment. Once these networks are buried and translated into the subsurface, the coarse-grained channel fills serve as likely conduits for subsurface fluids such as water, oil, or gas. This talk will focus on a new method for building synthetic stratigraphy from surface imagery and will discuss how the temporal evolution of a delta topset can be used to constrain subsurface architecture.

Seds Online Student Webinar (SOSW 2): Influences of syndepositional deformation on sedimentation

Ariana Osman, Sebastian Reimann, and David Lankford-Bravo

Ariana Osman (The University of the West Indies) “The Changing Topset Regime and Clinoform Architecture on the Paleo-Orinoco Delta, Trinidad – A Story of Eustatic and Tectonic Interaction”

Sebastian Reimann (Friedrich Schiller University Jena) “Syndepositional Intrusion of the Lomati River Sill and Liked Hydrothermalism Preserves Records of One of the Earliest Benthic Ecosystems”

David Lankford-Bravo (The University of Texas at El Paso) “Investigating Permian-Aged Deposition and Deformation at the North Onion Creek Salt Shoulder”

True substrates: the inevitable preservation of ‘human timescale’ snapshots on ancient bedding planes

Neil Davies - University of Cambridge

Rock outcrops of the sedimentary-stratigraphic record often reveal bedding planes that can be considered to be true substrates: preserved surfaces that demonstrably existed at the sediment–water or sediment–air interface at the time of deposition. These surfaces have high value as repositories of palaeoenvironmental information, revealing fossilized snapshots of microscale topography from deep time. This talk will discuss ideas about how such true substrates are preserved, what they can inform us about ancient environments and stratigraphic time at outcrop, and why they seem to be so counterintuitvely abundant in the sedimentary record.

The 3D geometry of meandering channels: Implications for the stratigraphic record

Zoltan Sylvester - The University of Texas at Austin

Meandering channels are ubiquitous on the surface of the Earth, both on land and on the seafloor. Although there is a large volume of published research on meandering, relatively simple questions – like the prediction of migration rates – are still considered highly complex problems with no simple solutions. A comparison of a simple curvature-based model of meandering with measurements from rivers and submarine channels suggests that, in systems unaffected by significant variation in erodibility, migration rates can be predicted relatively well, based on channel curvature alone. Plan-view meandering patterns in nature, both fluvial and submarine, show many of the characteristics of this model: a spatial phase lag between curvature and migration that has a characteristic length and results in autogenic downstream translation of many meander bends and in deposition of counter point bars. If along-channel changes in slope are added to the model, the implications of the 3D geometry for incising and aggrading channels become obvious as well. We use open-source code to visualize the 3D geometry and temporal evolution of the deposits of both subaerial and submarine meandering flows.

Seds Online Great Debate: Sea Level Rise Drowns Reefs

Cecilia Lopez-Gamundi, Elias Samankassou, Edward Matheson, and Peter Burgess

Seds Online Great Debate

Topic: Sea Level Drowns Reefs

Arguing for the motion: Cecilia Lopez-Gamundi, Elias Samankassou

Arguing against the motion: Edward Matheson, Peter Burgess

From calcretes to travertines: are they good neighbours?

Ana María Alonso-Zarza - Director of the Geological and Mining Institute of Spain

Continental carbonates also, controversially, often referred to as ‘non-marine carbonates’ are intriguing and deserve our full attention. These land-formed carbonates contribute to our understanding of the Earth System and its imprint in the so called ‘critical zone’. Climate, biota, CO2 fluxes, parent material, aeolian dust, hydrology and even humans, interplay to form an impressive puzzle in which necessarily calcretes and travertines must be good neighbours.