Scientific Webinars

An introduction to OSL Dating and luminescence signals

Dr Gloria I. López – National Research Centre on Human Evolution (CENIEH) Recanati Institute of Maritime Studies (RIIMS) at the University of Haifa, Israel

“To see the World in a grain of sand… hold infinity in the palm of your hand and eternity in an hour” might be one of the best poetic descriptions for Luminescence Dating… sure, back in 1803, William Blake could not have imagined such scientific achievement! As a matter of fact, Optical Dating or OSL (Optically Stimulated Luminescence) has been one of the fastest growing dating methods since its development in 1985, in terms of protocol development, instrumentation and use. Who would have thought that a single ray of sunshine and the natural radioactive decay ever present in the environment would be allies for OSL signals to shine! As it uses two of the most abundant mineral grains available on the surface of the Earth (quartz & feldspars), OSL has a multitude of applications in addition to the ability to assign numerical ages to numerous environments and sedimentary deposits from the depths of the ocean to the highest peaks. In this presentation we will go over the basics of OSL Dating, and consider some of the major challenges, as well as the advantages. We will have a glimpse at the latest developments and applications, with a special focus on sedimentological and stratigraphical issues. One thing to bear in mind: OSL might not be used only for dating! The in-depth analysis of luminescence signals may give unforeseen insights into transport-deposition processes and events of both natural and anthropogenic origin.

A guide to Earth, life, and terrestrial carbonates for the intergalactic sedimentologist

Dr Alex Brasier – University of Aberdeen

If there were a guide book for the intergalactic sedimentologist then this would be the heavily-read chapter on terrestrial carbonates (principally those formed in soils, lakes, streams and springs). A reviewer might say that the examples used – although spanning a huge time range – are rather Earth-focussed. This largely reflects the travel budget of the author. But they would hopefully also say that this chapter is much more widely applicable to other planets, and that it contains beautiful pictures of all types of terrestrial carbonates. Readers would agree that hot-springs are great for holidays, but even the humble calcrete nodule can be invaluable for studying the co-evolution of life and environments on a planet.

Observing turbidity currents in the wild: New insights from direct field-scale measurements

Dr Mike Clare – National Oceanography Centre

Avalanches of sediment in the ocean, called turbidity currents, are among the volumetrically most important sediment transport processes globally. Due to their fast speeds, turbidity currents can break critical infrastructure, and transport organic carbon and nutrients far into the deep-sea, thus sustaining deep-sea ecosystems. Until recently, we have largely had to rely on the deposits that they left behind or small-scale flows held ‘captive’ in the laboratory to understand turbidity currents. New developments in technology now enable detailed and direct measurements of powerful flows at field scale to complement these studies. Here, we present recent measurements gathered by a large consortium of researchers from a range of shallow to deep-marine settings worldwide that provide new insights into the internal anatomy of these these flows, how they initiate, evolve and interact with the seafloor.

Clinothem architecture and sediment distribution in exhumed basin margin successions

Miquel Poyatos Moré – University of Oslo

Clinothems are the building blocks of basin margin successions, and can be subdivided into three physiographic segments: shelf (topset), slope (foreset) and basin floor (bottomset). These segments are defined according to the position of sedimentary transition zones, like the shelf-edge rollover and base of slope. These are zones with breaks in clinoform gradient, and their stratigraphic record and trajectory provide information about the balance between accommodation versus sediment supply, and sedimentary process interactions. However, the complete record of individual clinothems is rarely documented, mainly due to outcrop or subsurface dataset limitations. The Karoo Basin, in South Africa, exposes exhumed basin-margin scale clinothems with local across-strike control, which allows a) to provide sub-seismic characterization of topset-foreset-bottomset deposits along the same basin margin clinothem; b) to locate sedimentary transition zones and study the facies distribution both down depositional dip and across depositional strike; c) to establish the sequence stratigraphy of a margin transitioning from erosional- to accretionary-dominated; and d) to discuss wider implications for stratigraphic models of basin evolution.

Sequence stratigraphy of late Paleozoic cyclothems; a signal of sediment undersupply, large-magnitude sea-level changes and low accommodation

Professor Christopher R. Fielding – University of Nebraska-Lincoln

Cyclothems are stratal rhythyms comprising repetitive vertical successions of sandstones, heterolithic (thinly interbedded) sandstones and mudrocks, mudrocks, limestones, and coals, in many cases with pedogenic overprinting of these lithologies. They record repetitive alternations of shallow marine and coastal to nonmarine environments of deposition. They are typical of Carboniferous and Permian paleotropical successions across Euramerica. Controversy endures as to whether cyclothems were formed under external forcing or rather were the product of mainly autogenic processes. Careful mapping and correlation of cyclothem strata and use of a sequence stratigraphic methodology allows a fuller understanding of these enigmatic rhythms. Depositional sequences can be identified and correlated over 100s of km, based on the recognition of regionally extensive disconformity surfaces and the continuity of key marker beds. Erosional surfaces preserve deeply incised valleys, separated by relatively flat interfluves represented by pedogenically modified strata. Sequences bounded by these surfaces are < 2 to > 30 m in thickness, varying considerably in thickness and facies composition but nonetheless preserving predictable arrays of facies that record deepening and shallowing trends. Because of the limited thickness of cyclothems, it is difficult to apply the accommodation succession concept to these deposits. Rather, cyclothem sequences are thin, incomplete, condensed, strongly top-truncated, and have a ragged blanket geometry. Although the term “cyclothem” has been used in a variety of contexts, a definition of the term limited to successions that were deposited (1) on low-gradient pericontinental shelves in paleotropical regions, (2) as far-field products of Gondwanan glacial growth and decay at various timescales, and (3) under conditions of low sediment supply in most cases, and (4) under low accommodation limited by slow, passive subsidence is herein preferred.

Microplastics in sedimentary systems. What we know and don’t know about this new type of sediment particle

Dr Florian Pohl – Durham University

The threat posed by plastic pollution to ecosystems and human health is under increasing scrutiny and the amount of mismanaged plastic waste entering the environment is growing at a staggering rate. In particular microplastics (plastic particles <1 mm in size) have been discovered in every sedimentary system on the planet and thus became a new type of sediment particle. As such, sedimentology represents an important and powerful tool to understand and predict the transport, dispersal, and ultimate fate of microplastics in different environments. However, due to the complex shapes and low densities the transport and sedimentation behavior of this new sediment particle may differ significantly from those of natural sediments. The presence of microplastics in the environments poses new challenges for the field of sedimentology, but may also provide opportunities to better understand the dynamics of sedimentary systems. In this talk I will provide an overview on global plastic-pollution, microplastic as a new and unique sediment particle, and on microplastics in seafloor sediments.

Magnitude and drivers of short term sea level fluctuations in the Cretaceous: a review

Dr Franz van Buchem and Dr Andy Davies – Halliburton – Landmark

Based on a recent review of the literature a data base of absolute values of short term (<3my) Cretaceous sea level rises and falls has been created. This shows an overall amplitude range of 5 to >65m, organised in four broad trends. The potential of aquifer eustasy has been investigated using climate modelling which showed a maximum impact of 5 to 10 meters. This leaves Glacio-eustasy as the key driver for short term high magnitude sea level changes in the Cretaceous.

Building big bioherms from humble Halimeda: insights from a modern analogue

Mardi McNeil – Queensland University of Technology

The Halimeda algal bioherms of the Great Barrier Reef, Australia represent the largest living, actively accumulating Halimeda deposits worldwide. Following the Holocene post-glacial marine transgression, these bioherms kicked off the outer-shelf carbonate factory some 2000 years earlier than the nearby coral reefs. Recent multi-disciplinary work has revealed new insights into their surface geomorphology, subsurface architecture and depositional environment that may be of interest to those working on their fossil counterparts.