Quantitative analogue flume‐model study of river–shelf systems: principles and verification exemplified by the Late Quaternary Colorado river–delta evolution

Abstract

Physical modelling of clastic sedimentary systems over geological time spans has to resort to analogue modelling since full scaling cannot be achieved within the spatial and temporal restrictions that are imposed by a laboratory set‐up. Such analogue models are suitable for systematic investigation of a sedimentary system's sensitivity to allocyclic changes by isolating governing parameters. Until now, analogue models of landscape evolution were mainly qualitative in nature. In this paper, we present a quantitative approach. The quantitative experimental results are verified and discussed by comparison with high‐resolution data from the Colorado river–shelf system of the Texas shelf that we used as a prototype. The model's dimensions are proportionally scaled to the prototype, except for a vertical exaggeration. Time is scaled using a Basin Response factor to maintain a similar ratio between the period of change and the system's equilibrium time for model and prototype. A Basin Fill factor was used to compare the ratio between the time‐averaged sedimentation rate and the rate of change in accommodation space of model and prototype. The flume‐model results are in the form of sediment budgets that are related to shelf cannibalism and fluvial supply, which are compared with the ancestral Colorado river–delta evolution of the last 40 kyr. Model and prototype have similarities in delta evolution in response to one cycle of sea‐level change. With sea‐level change as the isolated variable, the flume model generates a significant supply pulse caused by headward erosion of the shelf in response to the sea‐level fall. This pulse adds to the yield of the hinterland. The supply induced by sea‐level change persists during the early rise, although its rate declines. A similar trend is observed on the east Texas shelf. We argue that shelfal and fluvial degradation cycles induced by sea‐level changes can significantly influence the timing and amount of sediment supply to basins and must therefore be taken into consideration.

Signatures of climate vs. sea-level change within incised valley-fill successions: Quaternary examples from the Texas GULF Coast

“…In fact, correlations between onshore and offshore records, such as that presented above for the Texas coastal plain and shelf records, demonstrate that long-held concepts of incision and complete sediment bypass during falling sea-level are not realistic, and that incision updip is not necessary to produce the volume of sediments required to produce systems tracts farther downdip. Van Heijst et al (2001) drew similar conclusions through experimental flume studies, and comparisons with the OIS 3 record of the Colorado River offshore.…”

Diffusive evolution of experimental braided rivers

“…The question of the statistics of channel network establishment was explored in a pioneering paper by Howard et al [6], in which the authors showed that braided channel paths exhibit scaling relationships similar to those derived from random walk models. At a larger scale, diffusion has been invoked as a useful tool to model landscape evolution in a variety of field and laboratory settings, including braided river equilibrium profiles [20,21,[25][26][27][28]. These macroscopic applications of diffusion to braided river evolution have not, however, been linked to underlying stochastic dynamics as in classical Brownian motion [29].…”

Towards a sequence stratigraphic solution set for autogenic processes and allogenic controls: Upper Cretaceous strata, Book Cliffs, Utah, USA

“…However, the results of numerical and physical stratigraphic modelling experiments are not straightforward to compare with outcrop and subsurface geological data, and have only sparingly been used as a basis to interpret observations made on such data (e.g. Muto & Steel 1992, 2002Van Heist et al 2001;Paola & Martin 2012). In this paper, I re-examine the stratal architectures exposed in continuous, large-scale outcrops of marginal-marine and shallow-marine strata (late Cretaceous Star Point Sandstone, Blackhawk Formation, lower Castlegate Sandstone and related strata exposed in the Wasatch Plateau and Book Cliffs, Utah and Colorado, USA), from which widely applied conceptual models of high-resolution sequence stratigraphy that invoke a relative sea-level control were developed during the 1980s and 1990s (e.g.…”