Zoltán Sylvester

@zzsylvester.bsky.social

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Research professor at UT Austin | geology | sedimentology | rivers | python | mountains | running | opinions are my own | he/him zsylvester.github.io

Title slide of the talk; the title is "The strange ordinariness of high-frequency signal preservation in the stratigraphic record".
High‐resolutionmulti‐beambathymetrydataoftheupperIndusFan -- Figure 2 from Kunnummal et al., 2026, JGR Earth Surface
"Can Al discover a new oil field?" was the keynote talk at The Geological Society of London's Al in the Geosciences conference yesterday. "Leaving hydrocarbons in the ground is suboptimal" is a literal quote from the talk. I attended the conference as both a speaker and a panelist. I was surprised to find that I was the only person in the (quite large) audience willing to speak up on the issue of climate change in response. As the UK's learned society for Earth Science, the Geological Society surely has a real responsibility to raise awareness of climate change, and to act. Geological knowledge supports society in so many ways, and so many of those are compatible and necessary for achieving global sustainability goals. We have a responsibility to celebrate endeavours that bring us closer to a sustainable future, rather than those that push such a future further from our reach.
Interdune muddy pond deposits with desiccation cracks in early morning light, surrounded by dune sands with two scales of ripples that are nicely highlighted by the low-angle light
Screenshot from a course evaluation form in which a student wrote "I really loved his jokes"
Formation of bounding surfaces with the migration of simple dunes (A) and the migration of draas (B). Illustration by Gary Kocurek; figure 1 in “First-order and super bounding surfaces in eolian sequences - Bounding surfaces revisited”, Sedimentary Geology, 56 (1988), 193-206.
A plot showing measured curvatures and migration rates along a meandering river and correlated using dynamic time warping. The two curves are quite similar, although the migration rate curve is shifted downstream by about two channel widths.
The rig is needed when you want to extract longer cores
The diffusion-assisted particle reconstruction model (DPRM) framework for 3D particle reconstruction from a single 2D image - Figure 1 from Zhu et al., 2025
Leonardo DiCaprio’s character in the movie “One Battle After Another”, saying “I don’t remember any more of this code speak”
Chart from the Strava app showing how my weekly relative efforts have changed during the last few months
The cover of the book “The Welch Land Illustrated Guide AI - A deep dive into modern AI”
One of the classic views of The Wave, an erosional feature carved into the Navajo Sandstone, largely into one foreset of cross bedding that shows seasonal cycles
Looking from above at the ~60 m wide neck left between the two bend segments. Flow is toward the top of the image on the left side, and toward the bottom of the image on the right side.
An image of gravel, with the largest grains shown in yellow, and the smallest ones in purple.
A cutting board built from pieces of wood of different colors do that it looks like stratigraphy cut by three normal faults. There is a dyke as well that pre-dates the faulting.
Two laminated pieces of core from the Castile Formation with alternating light and dark colored laminae that can be matched over a distance of 24 km
No Kings rally at Zilker Park, Austin; the city skyline in the background and a sign that says ‘Chinga tu MAGA’ in the foreground
Marathon times over the years
Sketch of superimposed small bedforms on a larger longitudinal / oblique bedform, with the smaller bedform crests being roughly perpendicular to the trend of the large dune. From Rubin and Hunter (1985).
Title and abstract of the Science paper by David Rubin and Ralph Hunter - Title: Bedroom Alignment in Directionally Varying Flows; Abstract: Many kinds of sediment bedforms are presumed to trend either normal or parallel to the direction of sediment transport. For this reason, the trend of bedforms observed by remote sensing or by field observations is commonly used as an indicator of the direction of sediment transport. Such presumptions regarding bedform trend were tested experimentally in bidirectional flows by rotating a sand-covered board in steady winds. Transverse, oblique, and longitudinal bedforms were created by changing only two parameters: the angle between the two winds and the proportions of sand transported in the two directions. Regardless of whether the experimental bedforms were transverse, oblique, or longitudinal (as defined by the bedform trend relative to the resultant transport direction), they all had trends that yielded the maximum gross transport across the bedforms. The fact that many of the experimental bedforms were neither transverse nor parallel to the resultant transport direction suggests that transport directions cannot be accurately determined by presuming such alignment.
Red and white cross bedding of the Navajo Sandstone, with evidence for smaller dunes migrating over larger bedforms - see the 'compound crossbedding' and 'superimposed-bed form cycles' obvious at the end of the animation (terminology of Rubin and Hunter, 1983)
Block diagram of a modeled meandering river, with the stratigraphy visible in the cross section in the front and scroll patterns are present on the point bars. Flow is away from the viewer.
Wedge-shaped grain flow deposits shown in orange color; the rest of the rock consists of either grain fall layers or wind ripples. Black-and-white square in middle is 20 cm across.
Histogram aligned with PCA main axis (matplotlib figure from the book "Scientific Visualization: Python + Matplotlib" by Nicolas Rougier)
Photo of fluvial gravel from Barton Creek, Austin, Texas (A), output of the segmentation (B), size distributions of the major and minor grain axes (C), and the area-weighted size distributions (D). Major grain axis lengths are shown in blue, minor grain axis lengths in orange.
Thick black line is the centerline of the Beni River in Bolivia. Circles that are tangent to the centerline represent the radius of curvature ag the location. Smaller circles = higher curvatures.
A simple model of river meandering shows how cutoffs lead to concave bank deposition (counter point bars)
Two oxbow lakes of similar orientation, filled with yellow-brown muddy water, and surrounded by a dense, dark green forest.
Moqui marbles line up in elongated patches that parallel eolian bedding in the Navajo Sandstone
Orthophotomosaic (derived from a drone model) showing large-scale eolian cross bedding in the Navajo Sandstone, with the typical Navajo colors
Eolian cross bedding in the Navajo Sandstone
The meandering planform of the Purus River (a tributary if the Amazon), shown as white wiggles on a black background. The width of the river and the size of the meanders are increasing downstream (top to bottom, left to right).
A few semi-transparent grains of sand on a black background, with a frosted texture characteristic of wind abrasion
White sandstone with polygonal weathering above deformed cross bedding and large blocks that are mostly red