PhD thesis: Disentangling time from siliciclastic sedimentary rocks

Tore Aadland’s PhD thesis titled “Disentangling time from siliciclastic sedimentary rocks”, successfully defended on 13 March 2019, is now available in the ARCEx intranet.

Summary:

This PhD project aims at improving our understanding of the distribution of time in siliciclastic sedimentary rocks. Our ambition is to develop source-to-sink method- ologies that takes advantage of sediment accumulation rate measurements derived from modern depositional systems. Three scientific papers that addresses various aspects of this problem has been prepared. The first paper addresses the time-scale dependence of sedimentation rates from a mass-balance perspective and shows that the non-linear relationship between the lengths, areas and volumes of growing objects require that time-averaged sedimentation rates are time-scale dependent when the rate does not capture all the directions the deposit has grown in. This provides a model by which to interpret anomalies in the stratigraphic completeness of sedimentary deposits. It offers a way to evaluate if this scaling effect is enough to explain the time-scale dependence of empirical sedimentation rate data. In the second paper we use Google Earth Engine to analyse Landsat 4, 5, 7 and 8 thematic mapper derived top-of-atmosphere corrected reflectance images acquired in the period 1984-2015 and generate a compilation of progradation rates for some of the deltas in an established dataset with catchment, climate and fluvial discharge properties. The result is a statistical model that given the water discharge and the suspended sediment load of a modern fluvial system predicts the progradation rates occurring at the fluvial entry points of the associated deltaic systems. In paper three we use the Upper Santonian to Middle Campanian Blackhawk Formation deposits in eastern Utah and western Colorado as a natural laboratory to test if we can use the model of modern progradation rates derived in paper two to understand the time captured by shoreline progradation recorded in ancient siliciclastic rocks. By comparing the progradation distances recorded within the sedimentary rock with modern progradation rates we could demonstrate that we need 40±30% of the time available, as constrained by biostratigraphic data, to account for the observed progradation. In summary; paper three outlines a source-to-sink methodology with potential application in reservoir mapping and greenfield exploration that is guided by the model of time-scale dependent sedimentation rates presented in paper one and uses a progradation rate model presented in paper two.

Reference: 

Aadland, Tore (2019): Disentangling time from siliciclastic sedimentary rocks. A dissertation for the degree of Philosophiae Doctor, March 2019. University of Bergen. [intranet]