[First Hit]

Datapages, Inc.Print this page

The Role of Climate Variation in Sequence Stratigraphy: Lessons from Analogue Modelling

Bijkerk, Jochem F.; ten Veen, Johan; Postma, George; Mikes, Daniel

Sequence-stratigraphic models for 5th to 6th order, glacio-eustatic sequences based only on relative Previous HitseaNext Hit-Previous HitlevelNext Hit variations result in simplified and potentially false interpretations. Glacio-eustatic Previous HitseaNext Hit-Previous HitlevelNext Hit variations form only one aspect of cyclic climate variation; other aspects of climate variation (e.g. variations in river run-off) can lead to variable sediment yield, thus adding complexity to sequence stratigraphic patterns normally attributed to Previous HitseaNext Hit Previous HitlevelNext Hit variation.

Based on analogue flume models, a significant impact of discharge is observed on the timing and character of sequence boundaries, as well as on changes in the relative importance (sediment volume expression) of Previous HitsystemsNext Hit Previous HittractsNext Hit. Four deltas, generated under influence of an identical Previous HitseaNext Hit-Previous HitlevelNext Hit curve, but affected by different discharge cycles are generated in the Eurotank Laboratories: (1) constant discharge; (2) high frequency discharge variations; (3) high discharge leading high Previous HitseaNext Hit Previous HitlevelNext Hit by a quarter Previous HitphaseNext Hit; (4) high discharge lagging high Previous HitseaNext Hit Previous HitlevelNext Hit by a quarter Previous HitphaseNext Hit. High frequency discharge variations show little impact on the overall delta architecture and might provide an explanation why 3rd order sequences in seismic generally do not show higher order climatic overprints. When high discharge leads high Previous HitseaNext Hit Previous HitlevelNext Hit, sediment delivery is high during Previous HitseaNext Hit-Previous HitlevelNext Hit rise, which results in the poor development of maximum flooding surfaces. Delta front erosion during Previous HitseaNext Hit-Previous HitlevelNext Hit fall occurs in multiple, small channels and does not result in a single connected, incised valley. In cases that high discharge lags high Previous HitseaNext Hit Previous HitlevelNext Hit, sediment delivery is high during falling Previous HitseaNext Hit Previous HitlevelNext Hit and results in rapid progradation during forced regression. Erosion from incised valleys is strong on the proximal delta top but dampened distally due to rapid progradation and valley backfill. During Previous HitseaNext Hit-Previous HitlevelNext Hit rise, low discharge result in sediment starvation and well-developed maximum flooding surfaces. Because Previous HitseaNext Hit Previous HitlevelNext Hit curves are identical in all models, the differences can be fully attributed to discharge variations.

Discharge variations thus provide an alternative explanation to the amplitude of Previous HitseaNext Hit-Previous HitlevelNext Hit fall for generating either Type 1 or 2 erosional unconformities. Based on the different responses of sediment yield to the delta apex, an influence of Previous HitseaNext Hit-Previous HitlevelNext Hit variations on the fluvial system is also inferred. A case study for scenario high discharge lagging Previous HitseaNext Hit Previous HitlevelTop high stand (scenario 4) is presented.

 

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013