The Impact of the Interaction Between High Frequency Climate Change and Glacioeustasy on Sediment Delivery to Ocean Margins
Chevron, Energy Technology Company, Houston, Texas, U.S.A
Climate and elevation are first order controls on sediment delivery to ocean margins. The largest changes in orbital-cycle-forced climate occur at the scale of procession (~20 kyr, significantly faster than elevation induced climate change. Consequently, a drainage area can be considered steady-state as orbital cycles shift seasonal insolation as much as 30% in as little as 10 kyr, causing major changes in climate, precipitation, runoff & river dynamics.
We have evaluated ~ 100 present day river drainage networks to develop a numerical model to forecast sediment yield for specific climates and elevations in order to investigate the impact on major paleoclimate shifts on drainage basins. The model that was developed has an accuracy of 86% (data/model correlation). Depending on the specific climate cycle affecting a region, river discharge and yield can change by an order of magnitude or more (rainforest to desert and visa versa, for example) over a precession cycle.
The timing of maximum sediment flux to an ocean margin is complicated by the fact that paleoclimate and sediment yield cycles are regional in extent while glacioeustatic cycles have a global signature. Consequently, the regional yield cycle of a fluvial system needs to be put in context with global sea level change to determine the timing of maximum sediment delivery to continental shelves. A global evaluation of fluvial systems shows that the highest sediment yields are not necessarily correlated with any specific phase of glacioeustasy (high, fall, low or rise). The timing of periods of high volume sediment yield relative to eustasy provides a method to forecast episodes of major transport events to deep ocean basins leading to the development of sand-rich submarine fans
AAPG Search and Discovery Article #90079©2008 AAPG Hedberg Conference, Ushuaia-Patagonia, Argentina