Research

Process-based alluvial architecture modelling

we evaluate the impact of cyclic and non-cyclic upstream forcing on alluvial stratigraphy through a process-based alluvial architecture model, the Karssenberg and Bridge (2008) model (KB08). We find cyclic alluvial stratigraphic patterns to occur when there is cyclicity in the ratio of sediment supply over water discharge (Qs/Qw ratio), in the precondition that the allogenic forcing has sufficiently large amplitudes and long, but not very long, wavelengths, depending on inherent properties of the modelled basin (e.g. basin subsidence, size, and slope). Larger Qs/Qw ratio amplitudes contribute to weaker downstream signal shredding by stochastic components in the model. Floodplain topographic differences are found to be compensated by autogenic dynamics at certain compensational timescales in fully autogenic runs, while the presence of allogenic forcing clearly impacts the compensational stacking patterns.

Mapping floodplain aggradation cycles in a drone-based photogrammetric model

Here, 44 floodplain aggradation cycles were mapped using an unmanned aerial vehicle (UAV) to develop a photogrammetric model covering a geographic area of ~10 km2 and spanning a stratigraphic succession of ~300 m. They have an average thickness of 6.8 m with a standard deviation of 2.0 m, which is in line with previous studies. Individual floodplain aggradation cycles may change in thickness rapidly when traced laterally, with rates up to 1 m over a lateral distance of 100 m and a maximum of 4 m. Detailed mapping of seven successive cycles reveals differences in their regionally-averaged thicknesses of 3.7 m to 9.7 m, with their coefficients of variation ranging between 17% and 28%. Variogram analysis demonstrates that the thickness of a cycle at one locality is statistically related to that at another locality over an average distance of 1.3 km in the paleoflow direction and 0.6 km perpendicular to the paleoflow direction. Two different metrics suggest that full-compensational stacking occurs after deposition of 6 to 7 cycles, or timescales of ca. 120 to 140 kyr, although strong thickness compensation is shown to start at the subsequent one and two floodplain aggradation cycles, so at ca. 20-40 kyr time scales. 

Sandstone body character, river styles, and geomorphology of the lower Eocene Willwood Formation, Bighorn Basin

Here, we study the characteristics and river styles of sandstone bodies through ca. 300 m stratigraphy in the McCullough Peaks. Sinuous and braided sandstone bodies differ significantly in average thickness (6.1 m versus 9.0 m) and insignificantly in average width (on average 231 m) and paleoflow directions (on average N003). Bighorn Basin margins varied in the early Eocene, with differing tectonic, geological, and topographic characteristics. The observed mixture of river styles may be attributed to differential influences of axial and transverse river systems and/or climate change that controls water discharge and sediment load. An early Eocene geomorphologic reconstruction is constructed summarizing these new and earlier results.

Predictable occurrences of channelized sandstone bodies of different fluvial styles linked to orbital climate forcing 

Here, we place 92 channelized sandstone bodies of different river styles within ca. 300 m georeferenced digital alluvial stratigraphy straddling 44 precession-driven floodplain aggradation cycles. We find some intervals dominated by sinuous channels and some other intervals by braided channels. The age control by the early Eocene carbon isotope excursions related to ETM2 and H2 and the 44 precession-controlled floodplain aggradation cycles, allows comparison with an eccentricity target curve. This strongly suggests that the braided-dominated interval occurs during 405-kyr eccentricity minima and the sinuous-dominated interval occurs during 405-kyr eccentricity maxima. The genetic links between river styles and orbital climate forcing remain to be unlocked. A preliminary model could be to link flashy precipitation and runoff, less dense vegetation cover, and increased  sediment load to eccentricity minima to the braided systems, and more constant runoff and lower sediment loads to eccentricity maxima, similar to previously proposed eccentricity-controlled landscape (in)stability phases.

Locating PETM and evaluating the fluvial response to it in the Rosebank block, North Sea

• Literature study into PETM impact on Qs, Qw, fluvial style, alluvial stratigraphy. 

• Pilot alluvial stratigraphic models of PETM impact on stratigraphy. 

• 13C record to build a record for the PETM in the Colsay 3 stratigraphy. 

• Litholog Colsay 3 cores and alluvial stratigraphic interpretation. 

• Alluvial stratigraphic model focussing on Colsay 1 and 3 reservoir sandstones 

• Report on the uncertainty and potential lines to decrease that

Particle image velocimetry of braided channel initiation

In this paper we investigate how migration patterns of braided rivers change through time and over space in a 37-m long flume basin, using the newly developed topography-based particle image velocimetry (PIV).