Future Webinars

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)

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?

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.

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.

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.

Seds Online Student Webinar (SOSW 4): Exploring sediment transport dynamics from source to sink

Presenters: TBD