Scientific Webinars

Submarine-channel meandering and salt-basin filling

Jacob Covault - The University of Texas at Austin

Many continental margins show submarine-channel patterns that resemble meandering rivers on land. How exactly do submarine channels evolve and disperse sediment and dissolved loads throughout the ocean? Do submarine channels migrate in a way that is similar to rivers? Whereas platforms like Google Earth Engine have enabled broadly accessible, global-scale analysis of rivers in Landsat imagery, this is difficult to do underwater. We used 3D seismic-reflection data to interpret the evolution of some of the largest submarine-channel systems ever recorded offshore Brazil. The margin offshore Brazil has complex topography, with many salt domes that have steered and deflected the submarine channels since the Cretaceous. We applied our experience in mapping and interpreting the time-lapse evolution of rivers in Landsat data to analyze the evolution of the submarine channels offshore Brazil. Our results show that early during the evolution of the submarine channel it migrated like a freely meandering river. However, as the submarine channel expanded toward nearby salt domes, its migration pattern fundamentally changed. With nowhere to expand further, the submarine channel translated downstream to produce a pattern characteristic in rivers that are confined by banks resistant to erosion.

A Jurassic Lost World: seismic imaging of the drowned topography at the base of the Louann Salt (Gulf of Mexico) reveals how the evaporite giant was deposited

Frank Peel and Gillian Apps - Bureau of Economic Geology

3D seismic imaging of the base of the giant Bajocian Louann Salt evaporite reveals, in exquisite detail, the nature of the pre-salt landscape. An arid desert terrain contains a network of incised rivers (wadis) flowing into a large, incised, meandering river, in turn flowing into a large lake in the middle of the basin. This lake was >1km deep, and its surface was ca. 750m below Bajocian sea level. At 170MA, a connection to the Tethys Ocean was opened, and the desert basin was flooded, allowing deposition of the salt in a deep-water basin. Simple calculations indicate that salt deposition was extremely rapid, with the entire multi-km thickness of salt deposited in a few tens of thousands of years.

Investigating heterogeneous geochemistry of brines and sediments from the Salar de Llamara: A case study from a polyextreme environment

Amanda Oehlert – University of Miami

The Atacama Desert is home to a variety of extreme environments. It includes salt flats, with wide ranging age, chemistry and styles of mineral deposition. One of these extreme environments is the Salar de Llamara which contains more than 400 saline lagoons and peripheral ponds locally called “Puquios”, with a diverse range in brine chemistry and sedimentation styles which appear to result from the complex interplay between physical, chemical, and biological processes. In this talk, the major characteristics of the Puquios will be presented, and heterogeneity of lagoon chemistry and five sediment cores will be evaluated to provide insight into environmental reconstruction of extreme environments.

Late Early Jurassic environmental perturbations: a shallow-water perspective

Stéphane Bodin – Aarhus University

Neritic environments, host of the highest marine biodiversity, are particularly sensitive to environmental changes. Their study allows us to understand how carbonate-producing ecosystems cope with climatic upheavals, but also shed important light on the evolution of critical parameters such as global sea-level fluctuations during these contorted times. This presentation will focus on the late Plienbachian – early Toarcian time interval, which is marked by repeated drastic environmental changes, out of which the Toarcian OAE stands as one of the most extreme environmental change of the Mesozoic. By looking at an exceptionally preserved geological record in the Central High Atlas Basin of Morocco, the role and weight of different environmental factors (such as seawater temperature, oxygen and nutrient levels, carbonate saturation state, sea-level change, etc.) on neritic carbonate production and demise will be discussed.

Seds Online Great Debate: The Recent Really is the Key to the Past

Jeff Peakall, Shahin Dashtgard, William McMahon, and Cathy Hollis

Seds Online Great Debate

Topic: The Recent Really is the Key to the Past

Arguing for the motion: Jeff Peakall (University of Leeds) and Shahin Dashtgard (Simon Fraser University)

Arguing against the motion: William McMahon (University of Cambridge) and Cathy Hollis (University of Manchester)

What does a glacial deposit really look like, and what is “normal” in Earth’s sedimentary record of glaciation?

Dan Le Heron – University of Vienna

When we look at modern, Alpine glacial landscapes, we are struck by the abundance of chaotic and poorly sorted material, bearing large boulders. This material is diamict: unsorted, boulder-bearing material that is fashioned into a variety of familiar glacial landforms called moraines, and sometimes streamlined structures (drumlins). Earth has experienced many glaciations, and has a rich record of diamictites stretching from about 2.2 Ga to the present day. However, even superficial investigation reveals that the records of many glacial periods such as the Cryogenian and Late Ordovician are greatly contrasting. Cryogenian rocks crop out spectacularly in places like South Australia, Namibia, Scotland and the western USA. They are associated with no convincing glacially striated pavements anywhere in the world. This is in spite of these being associated with a so-called “snowball Earth”. Spectacular, thick diamictites are interbedded with abundant dropstone-bearing strata and thus testify to a glacial influence, but not all diamictites are glacial and many record mass failures of slopes in a marine environment. By contrast, there is a high abundance of these features recording subglacial erosion in Late Ordovician and Late Carboniferous records. Huge networks of palaeo-ice streams can be mapped from satellite data, to allow detailed ice sheet reconstruction. The deposits of the Late Ordovician glaciation are predominantly sandstone, supercritical flow deposits are abundant, and most of the subglacial record records shearing of soft-sediment rather than “traditional” scratches on bedrock. Examples of these deposits are in Morocco, Algeria, Libya and Saudi Arabia. The Late Carboniferous record includes palaeo-fjord systems (e.g. in Namibia and Argentina) with polished bedrock surfaces that closely resemble Pleistocene fjord systems. Approaching the glacial record often requires “out of the box” thinking, because the present is not always the key to the past. This begs the question as to which glacial period, if any, is truly representative in terms of a glacial sedimentary record on Earth. So, do we really know what a glacial deposit looks like?

The Contourite-Turbidite Controversy after 50 years

Dr Dorrik Stow – Heriot-Watt University

Ever since the contourite revolution of the 1960s the distinction between contourites, turbidites and hemipelagites in modern and ancient deepwater systems has been controversial. This is partly because: (a) the processes themselves show a degree of overlap as part of a continuum, so that the deposit characteristics also overlap; (b) the three facies types commonly occur within interbedded sequences of continental margin deposits; and (c) much erroneous and misleading material has been published over the past five decades. However, the nature of these end-member processes and their physical parameters are becoming much better known, and the occurrence, architecture and seismic attributes are now well established. Good progress has also been made in recognising differences between end-member facies in terms of their sedimentary structures, facies sequences, ichnofacies, sediment textures, composition and microfabric. These characteristics can be summarised in terms of standard facies models, and the variations from these models that are typically encountered in natural systems. Nevertheless, it must be acknowledged that clear distinction is not always possible on the basis of sedimentary characteristics alone, and that uncertainties should be highlighted in any interpretation. Controversy remains and clearly focused new research is much needed.

Fluvial models: how much variability should we see? Lessons from the Huesca and Salt Wash fluvial systems

Dr Amanda Owen – University of Glasgow

Geological models are important in aiding our interpretation of the rock record, particularly where outcrops, or subsurface data, is sparse. Conceptual models have been built and published for distributive fluvial systems (e.g. fluvial fans) where a predictive downstream and temporal changes in fluvial characteristics (e.g. channel body size) are present. However, few studies have assessed how much variability is observed across such systems and therefore should be present within our predictive models. This talk will present work that assesses how much variability can be present within facies models. Focusing on recently collected data from the Huesca distributive fluvial system (Spain) with comparison to the well-documented Salt Wash distributive fluvial system (SW USA).

Coralline algae made simple: tips for using red calcareous algae for paleoenvironmental reconstruction of Miocene carbonates

Dr Giovanni Coletti – University of Milano Bicocca

Coralline algae are one of the most common carbonate producers in shelf environment, occurring from the poles to the equator and from the intertidal zone to the lowest limit of the photic zone. Notwithstanding their abundance (and several attempts throughout the years), they remain a relatively underused instrument for studying shallow water limestones. This is mainly caused by the complicated and ever shifting taxonomy and by the inherent difficulties in dealing with a macroscopic object which requires a microscope for proper identification. This talk aims at providing a couple of useful and time-effective strategies to use coralline algae for paleoenvironmental reconstructions focusing on the Miocene, an epoch where these carbonate producers are particularly widespread and common.

Biotic, abiotic, pre-biotic, post-biotic controls on carbonate and phosphate formation

Dr Emilia Jarochowska – Friedrich-Alexander-University

Organisms can produce minerals with highly controlled crystallographic texture, either as a necessity resulting from growth mechanism, or to achieve desired material properties. But they will not shy away from abiotic mechanisms of crystal formation when they can exploit them. What is more, the crystallographic texture of originally highly-controlled biominerals can be altered by diagenesis. As a result, instead of a clearly defined biologically controlled and abiotic minerals, there is a spectrum of textures occurring in nature. In deep-time marine minerals, the crystallographic properties and their preservation may be the key to identifying the biotic origin of a structure and even its biological affinity (microbial or metazoan). This talk will provide a short overview of Electron Backscatter Diffraction and its use in studying fossil carbonates and phosphates, including sample preparation and data analyses important in resolving the processes of their formation.

Tide-dominated and tide-influenced depositional systems

Dr Marcello Gugliotta – University of Bremen

Tide-dominated and tide-influenced systems have been investigated for several decades, attracting the interest of many sedimentologists; nonetheless, these depositional systems remain poorly understood compared to their fluvial-dominated and wave-dominated counterparts. Interpreted tide-dominated successions show mismatches with their modern analogues when comparing grainsize, architectural elements, unit thicknesses and others. Sedimentary structures considered as “tidal indicators” can also commonly be found in non-tidal environments. Yet, they are often used as the only tool to infer a tidal origin for ancient systems, driving the development of (misleading) conceptual and applied models. During this seminar, I will show some examples of modern and ancient tidal systems, discussing some of the problems related to their investigation.

Reconstructing flow properties and depositional environment from sole marks: The first field test

Dr Jaco Baas- Royal Hoilloway, Bangor University

Bedforms and their primary current stratification are used routinely as indicator of flow type and flow strength. It has recently been advocated that sole marks could be used in a similar way, particularly for depositional, non-bypassing, flows. This presentation reveals, for the first time, that predictable relationships exist between sole mark type and size, flow type, deposit type, and depositional environment, based on field data from the Aberystwyth Grits Group (Silurian, West Wales, U.K.)

Do you go with the flow? Contourite and Mixed depositional systems

Dr Javier Hernandez-Molina – Royal Hoilloway, University of London

Along-slope bottom currents, and associated oceanographic processes, can trigger large- and small-scale deep-water processes that interact with other hemipelagic and gravitational processes, generating Contourites and Mixed (or Hybrid?) Depositional Systems, depending on the relative contribution of each type of process behind the scenes. The very recent explosion of examples described in either academic or industry research on the deep-marine sedimentation has no doubt contributed to a better understanding of these systems. New models are being proposed and there is a growing interest in these systems, in their origins, their deposits and evolution, their relationship with deep-sea ecosystems, geological hazard, and even their economic potential. Nevertheless, we lack some essential knowledge about their genetics, interrelations and evolution over time. This talk is intended to present the basic (confirmed or proposed) concepts regarding Contourite and Mixed Depositional Systems, offering examples from modern oceans and ancient records, from 2D and 3D seismic scales to the sedimentary facies scale, highlighting the role of bottom currents in shaping the sea-floor and controlling the sedimentary stacking patterns of deep-water sedimentary successions. Future considerations are then put forth, so that the newly enlightened audience, especially students and young researchers, may more readily to “go with the flow”.

The fingerprint of environmental change in the aeolian sedimentary record

Dr Nigel Mountney – University of Leeds

Aeolian sedimentary systems are sensitive to changes in multiple environmental variables, including climate, sea level, sediment supply and tectonic controls. As such, the preserved sedimentary deposits of aeolian dune fields record a fingerprint of past environmental change. A combined field-based, remote-sensing and modelling approach is used to characterise a variety of different types of aeolian sedimentary system and their preserved successions. A suite of generic models is developed and applied to enable regional palaeoenvironmental reconstructions of desert systems that evolved during different periods in earth history, and in different palaeogeographic settings, in response to changing environmental conditions. These models are applied to predict sediment-system response to future environmental change, especially desertification arising from on-going climate change.

The ichnology of carbonate drifts

Dr Jesús Reolid Pérez – University of Granada

Carbonate drifts are interesting sedimentary environments for understanding past palaeoceanographic and palaeoecologic conditions. Carbonate drifts are typically studied at large scale with seismic profiles or a meter scale by sedimentological analysis, however the study of the bioturbation on such deposits can provide more detailed information about the palaeoenvironmental conditions at the seafloor.

Fates of World Major River-Derived Sediments to the Sea: Along-shore vs Cross-shelf Transport

Dr J. Paul Liu – North Carolina State University

Recent extensive geological and geophysical surveys over the world major river-dominated sea margins indicate that many rivers have developed largest proximal subaqueous deltas, with asymmetrical prodelta lobes, and elongated or detached distal masses of sediment. For example, the Amazon River’s sediment disperses >1500 km along the shore within the water depths of 60-70 m, and reaching the Orinoco River mouth; The Yangtze River sediment has transported ~800 km along the shore into the Taiwan Strait, and Yellow River sediment is deposited more than 700 km into the south Yellow Sea. Beyond the proximal depocenters near their river mouth, both the Yangtze and Yellow systems have developed a 40-m thick distal mud depocenters. The Mekong-derived sediment has also extended >250 km southwestwardly to the tip of the Ca Mau Peninsula, forming a distal mud depocenter up to 22 m thick, and extending into the Gulf of Thailand. Other major river systems, like the Irrawaddy, Mississippi, Nile, Po, Rhone, Pearl, Red, also have a large longshore-transported distal deposit with some typical underwater clinoform features. Only a few of the world major rivers are able to disperse their sediment directly or indirectly to the deep sea through the attached shelf canyon systems, like the Congo and Ganges-Brahmaputra.I will describe the unexpected discovery of pore fluids that, for the first time, appear to represent a direct archive of ancient seawater and to preserve the salinity and isotopic ratios of seawater from a past glacial period, likely the Last Glacial Maximum. These pore fluids were extracted from sediment cores from the Maldives Inner Sea, drilled in 2015 during IODP (International Ocean Discovery Program) Expedition 359 and penetrating late Oligocene to modern sediments. The composition of these fluids carries implications for glacial ocean circulation, water-rock interaction in platform systems, and preservation of carbonate sedimentary geochemistry.

An archive of glacial seawater and implications for carbonate platform sediments

Dr Clara Blättler – University of Chicago

I will describe the unexpected discovery of pore fluids that, for the first time, appear to represent a direct archive of ancient seawater and to preserve the salinity and isotopic ratios of seawater from a past glacial period, likely the Last Glacial Maximum. These pore fluids were extracted from sediment cores from the Maldives Inner Sea, drilled in 2015 during IODP (International Ocean Discovery Program) Expedition 359 and penetrating late Oligocene to modern sediments. The composition of these fluids carries implications for glacial ocean circulation, water-rock interaction in platform systems, and preservation of carbonate sedimentary geochemistry.

Always a White Christmas in the Bahamas: Ocean Chemistry & Hydrodynamics Focus Mud Production on GBB

Dr Sam Purkis – University of Miami

Whitings, or occurrences of fine-grained carbonate within the water column, have been observed in modern environments with salinities ranging from fresh to marine conditions, and thick deposits of lime mud are described throughout the geological record. Despite their ubiquity, the trigger for whitings has been a conundrum under debate for more than eighty years. This talk will review the trigger for whitings atop the Great Bahama Bank and call upon hydrodynamic simulation and geochemical modelling to explore the diverse triggers of the lime mud factory. The results have implications for the interpretation of whitings mud in the geological record, including the geochemical signatures within it.

A microbial ecosystem in the 3.48 Ga Dresser Formation, Pilbara, Australia

Dr Nora Noffke – Old Dominion University

The Archean Pilbara Block in Australia is known to host some of the oldest fossils in Earth history. This presentation focuses on microbially induced sedimentary structures (MISS) in clastic sabkha deposits of the Dresser Formation. Similarities of modern and fossil MISS suggest that already in the early Archean time complex microbial ecosystems existed.