Research

Reconstructing paleohydraulics from sedimentary deposits

The ability to quantify ancient channel geometries, flow conditions, and sediment transport conditions from sedimentary deposits is a crucial step to characterize ancient landscape dynamics. In the field, I make detailed measurements of channel deposits, and I apply geomorphic and hydraulic models to these measurements to reconstruct channel geometries, flow conditions, and sediment transport conditions. I also develop these methods. To date, this has included (i) developing paleohydraulic reconstruction workflows, (ii) evaluating paleohydraulic reconstruction methods, (iii) upscaling experimental observations to stratigraphy to advance paleohydraulic reconstructions, (iv) developing an empirical method of predicting paleo-planform, and (v) developing a modeling method of predicting ancient river intermittency.

Current/future questions: Can we quantify discharge variability from channel deposits? Can we use channel deposits as a proxy for terrestrial hydroclimate? To what extent can we apply paleohydraulic reconstructions to channel deposits on Mars?

From Lyster, Imperial College London PhD Thesis, 2022.

Ancient landscape evolution

I regularly conduct fieldwork to characterize ancient landscape dynamics. Field data collection involves facies observations, architectural analysis, and detailed measurements that I later use for paleohydraulic reconstructions. In the field, observations can be made at grain, bed, bar, channel, and channel-belt scales. At each of these scales, deposits reflect different timescales and processes of landscape evolution. Therefore, I collect data across multiple observation scales to build a complete picture of how these ancient landscapes evolved. To date, I have worked alluvial fan, fluvial, and deltaic deposits in Utah, Wyoming, and Colorado, USA, the Pyrenees, Spain, South Wales, UK, and more.

Current/future questions: What determines whether environmental signals are preserved at each observation scale? At which scales can we detect landscape response to tectonic or climatic change?

River response to climate change

Understanding how ancient rivers responded to climate change is crucial to predict how modern rivers may respond to current and ongoing warming. I have conducted extensive fieldwork to document and reconstruct river response to the Paleocene-Eocene Thermal Maximum (PETM), a global warming event that occurred ~56 million years ago. I have investigated river deposits that coincide with the PETM in multiple locations, including the (i) Pyrenees, Spain, (ii) Wyoming, USA, and (iii) Colorado, USA.

Current/future questions: Is the sedimentary record of river response to climate change biased to wetter or drier conditions? How did ancient rivers respond to other hyperthermals in Earth history?

Physical sedimentology experiments

Physical experiments allow us to bridge the gap between the timescales recorded in ancient deposits and modern deposits. I set up the new CoLD Group delta basin at The Pennsylvania State University, and I designed and ran a set of experiments to investigate how vegetation impacts delta behaviour. Specifically, I investigated (i) how channel mobility varies between non-vegetated and vegetated deltas, (ii) how sea level rise impacts delta channel mobility for non-vegetated and vegetated deltas, and (iii) how vegetation impacts deltaic stratigraphy.

Current/future questions: Do the differences between non-vegetated and vegetated experimental deltas help us to interpet the pre-vegetation rock record? How does vegetation impact the frequency of alluvial hazards (e.g., avulsions, overbank flows) on deltas?

Modeling land-ocean sediment fluxes

The ability to reconstruct sediment fluxes in ancient catchments is important for understanding the coupling of climate, tectonics, and surface processes over geological timescales. It is also important for identifying major depocentres throughout Earth history. In my work, I leverage palaeogeographies, palaeoclimate model outputs, and numerical models to predict sediment fluxes and erosion rates in ancient catchments. Similarly, I use modern geographies, modern and future climate projections, and numerical models to predict how sediment fluxes and erosion rates in modern catchments may change with ongoing global warming.

Using modern systems to understand ancient systems

Observations from modern river catchments can help us to interpret processes in ancient river catchments. I regularly compile data from literature for  modern systems, and from these data I try to find simple predictors of specific geometries/processes that can be applied to ancient systems. For example, I developed a large database of river planform as a function of channel aspect ratio and channel slope (see figures to the left) which, where data are scarce, can be used to predict ancient channel planform.

I also leverage open access datasets of modern catchments, modern climate, and other parameters to make observations of modern river catchments. I use these datasets to map catchment-averaged characteristics, for example, catchment-averaged discharge variability metrics (see figures to the right). Where appropriate analogs can be identified, I use catchment-averaged modern observations to help interpret processes in ancient river catchments.