Scientific Webinars

Recent time-lapse bathymetric data from modern deep-water channels reveal steeper gradient steps or knickpoints that can migrate rapidly upstream at rates of 100s m to kms per year. But what sort of fingerprint might these leave in the geological record? The knickpoints can erode down metres to 10s metres and hence should exhume relative stiff substrates, they typically have a vee-shaped planform and hence should perturb the flow field of turbidity currents passing over them, and as they migrate rapidly upstream, the flow state should evolve ‘at a point’ from supercritical as the higher gradient knickpoint migrates past followed by a hydraulic jump zone and then subcritical flow. In this talk, we will review the characteristics of a range of curious small scale (10s cm) scour-and-fill structures in the axial sandy facies filling Bashkirian turbidite channels in the upper (and more proximal) Ross Sandstone Fm, western Ireland, and consider a possible link to cyclic steps and knickpoint migration.

The length and dimensions of submarine channels can rival or exceed the largest rivers on land, and they produce the largest sediment accumulations on Earth.  However, there were previously no direct flow-measurements at the end of a submarine channel in the deep-sea. This led to the assumption that sediment transport to the end of submarine channels occurred for only a small (< 0.5%) fraction of the time, via infrequent but unusually powerful and erosive ‘canyon-flushing’ flows. However, here we show the termination of the Congo Submarine Channel is active for ~15% of the time, during a 14-month period without canyon-flushing flows, with individual flows lasting for a week to a month. This is despite the channel’s termination being situated >1,000 km from shore (measured along the channel-axis) at a water-depth of ~5 km. The flux of sediment from the end of this submarine channel rivals that supplied by the Congo River to its head. Frequent, sustained and exceptionally (~100%) efficient transfer of sediment and organic carbon transfer thus occurs over extremely long distances. This leads to unusual deep-sea ecosystems, and rapid (~10 km/yr) submarine channel extension due to a previously unknown mechanism involving non-erosional mud-flows rather than coalescing erosional scours.

A turbidity current measured at the end of the Congo Canyon-Channel at 5,000m water depth and some 1,000 km from the coastline

Interpretation of past environments from carbonate rocks is a challenging endeavor. Remains of different groups, taphonomy, chemical, and physical processes all result in an integrated hodgepodge which may be interpreted in more than one way. But this ambiguity is rarely fully acknowledged or accounted for. This talk will examine the inherent non-uniqueness in carbonate facies and what we can still infer from them, nevertheless.

Dryland fluvial systems exhibit interesting sedimentary facies and the spatial extents and downstream variations in sedimentary architecture can be quantified. However, reservoir models capturing the detail and variations of these depositional systems are limited. In this webinar we will travel (virtually) to the southwestern USA to examine the Lower Jurassic Kayenta Formation and investigate how the detailed sedimentary architecture of this dryland fluvial system can affect reservoir characterisation and fluid migration for CO2 storage.

The Lower Mississippi River near Natchez, USA, has experienced a prolific series of floods over the past 15 years that have resulted in overbank sedimentation in the embanked floodplain. Analysis of overbank sediment samples following floods coupled with floodplain sediment cores indicates that depositional thicknesses, rates, grain sizes, organic carbon, and nutrient concentrations vary with sub-basin inputs, flood magnitude and duration, and historical trends associated with land-use and flood mitigation efforts.

Investigating taphonomic processes affecting calcareous remains of invertebrates near the sediment-water interface and in the mixed layer in Holocene and Anthropocene marine environments on the basis of postmortem age-frequency distributions is informative about how mixing and disintegration change downcore, how they affect preservation potential and stratigraphic resolution, and whether taphofacies can be informative about how much time do the skeletal-bearing deposits actually contain (taphonomic clock). This talk will several approaches that can be used to assess the taphonomically-active zone, with empirical examples from the northern Adriatic Sea and the southern California shelf.

Sediments have long been a source of invaluable information about the Earth’s life history. The advent of ancient sedimentary DNA has opened a new window into this history. New opportunities include tracking the distribution of specific species across time and space and reconstructing entire ecosystems dating back as far as 2 million years. Today, the field is on the cusp of taking another transformative step in studying the past —tracking evolutionary processes of a broad spectrum of organisms, from viruses and bacteria to higher plants and animals. Achieving this breakthrough depends on developing novel wet lab and computational methods. Sedimentary microfossils lie at the centre of these efforts. Diverse, abundant, and well-preserved in various depositional environments worldwide, microfossils originate from organisms across the tree of life. As such, microfossils hold the potential to provide an unprecedentedly detailed study of evolutionary histories from sediments. However, this potential comes with challenges, including the complexities of isolating microfossils from sediments at scale and efficiently retrieving their DNA. This talk will introduce the exciting opportunities and practical challenges of working with microfossil DNA, with pollen as a case study, and provide an overview of the methodological developments underway.

Over the last three years, I have made more than 500 visits to a new dam project, located 15 km west of Calgary. New findings resulting from fieldwork on terrestrial deposits of the uppermost Cretaceous include a marine incursion, two new regional lowstand events, a new structural interpretation supported by some stunning drone data, and fossils ranging from dinosaurs to invertebrates to a new family of fossil plants. All this plus a bed of giant oncoids flagging up the K/Pg boundary, with everything underpinned by classic sedimentology. The project showcases Alberta’s Historical Resources Act in action on a major construction project.