3D Geostatistical Interpolation and Geological Interpretation of Paleo-Groundwater Rise in the Holocene Coastal Prism in the Netherlands
Kim M. Cohen, 2005. "3D Geostatistical Interpolation and Geological Interpretation of Paleo-Groundwater Rise in the Holocene Coastal Prism in the Netherlands", River Deltas–Concepts, Models, and Examples, Liviu Giosan, Janok P. Bhattacharya
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Coastal-prism sediments record rising local water levels, forced by sea-level rise. Sea-level rise is the primary driving factor, but the anatomy of the coastal prism is a result of a complex interplay of sea level, subsidence, and upstream controls (essentially sediment load). The sedimentary architecture of a coastal prism is linked to paleo-groundwater rise. Groundwater rise is quantified for the entire Rhine-Meuse delta (extending 120 km inland, 60 km wide) between an 11.0 kyr BP groundwater lowstand and the present highstand, dating series of organic markers (peats) of paleo-groundwater levels at compaction-free locations. The accumulated dataset of paleo-groundwater-level markers (> 300 index points) has a dense spatial and temporal coverage and a predictive quality that enables geostatistical analysis. The combination of this dataset and a carefully designed interpolation method (a form of 3D kriging) reveals the interplay between upstream (climate, discharge) and downstream (sea level, tides) controls on gradients of groundwater level and patterns of groundwater rise. Regional effects due to local controls (differential subsidence, groundwater flow) are also identified.
It is shown that backfilling of the paleovalley continues into the late Holocene, when eustatic rise had ceased, while at the same time the delta is prograding in the backbarrier area. The results corroborate earlier results regarding differential subsidence and postglacial enhanced subsidence rates (relative to long-term background rates) in the delta. Moreover, the 3-D geostatistical interpolation opens possibilities to test and further develop process-based models for deltaic deposition.
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Deltas are amongst the most environmentally and economically important coastal sedimentary environments. Studies of deltas lag behind research in both fluvial and deep-water depositional systems, as well as more geomorphologically oriented land studies. This knowledge lag reflects both a reorientation of the petroleum industry in the last two decades toward deep-water systems, as well as the difficulty of working across the shoreline with the traditional tools used for oceanographic or land-based work. However, deltaic studies are experiencing a renewed focus, because of their global importance in environmental and other societal concerns. This volume stems from a special session: Deltas: Old and New, held at the Annual Geological Society of America conference in October 2002, that was convened to highlight these new directions in deltaic research.