2026 CSDMS meeting-019
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Sediment Partitioning and Shoreline Response to GIA-Driven Basement Deformation in Arctic Deltas
Viet Bui,
(he/him),University of Florida Gainesville Florida, United States. buiv@ufl.edu
Jorge Lorenzo-Trueba, University of Florida Gainesville Florida, United States. jlorenzotrueba@ufl.edu
Tamara Pico, University of California Santa Cruz Santa Cruz California, United States. tpico@ucsc.edu
Emma MacKie, University of Florida Gainesville Florida, United States. emackie@ufl.edu
Jerry Mitrovica, Harvard University Cambridge Massachusetts, United States. jxm@eps.harvard.edu
In the Arctic, post-glacial isostatic adjustment (GIA) generates spatial gradients in vertical land motion that directly modulate accommodation space and sediment partitioning across deltaic systems. For the Mackenzie Delta (Northwest Territories, Canada), prior GIA modeling indicates strong vertical land motion gradients aligned with the primary direction of delta growth, with inland rebound uplift and offshore peripheral bulge subsidence producing spatially variable relative sea-level (RSL) trajectories along the N–S axis of progradation over small spatial scales (~40 x 40 km) and millennial timescales. Perpendicular to this direction of growth, vertical land motion varies more subtly along the east–west (lateral) axis. Superimposed on these GIA-driven patterns, the delta prograde over a strongly asymmetric pre-existing bathymetry shaped by the Mackenzie Trough, which imposes a persistent westward tilt on the basement surface.
To understand how spatially variable basement motion and inherited bathymetry jointly influence delta evolution, we develop an extension of a reduced-complexity, moving-boundary model derived from heat-transfer physics that explicitly incorporates time-dependent basement deformation driven by GIA. The model resolves shoreline migration and sediment partitioning between the fluvial region and the submerged offshore domain, operating at a level of complexity suited to data-limited Arctic settings and emphasizing first-order geometric observables that reflect sediment partitioning and RSL variability.
Applying the model to the Mackenzie Delta, we find that north–south uplift–subsidence gradients exert a primary control on sediment partitioning between subaerial and subaqueous domains, amplifying shoreline retreat and offshore sediment storage. In contrast, east–west variations in sediment thickness arise primarily from lateral bathymetric relief associated with the Mackenzie Trough rather than differential GIA forcing. Together, these results highlight the coupled roles of GIA-driven accommodation change and pre-existing topography in shaping Arctic delta morphology and stratigraphy.
