The pattern of sediment sequestration is an important controlling factor in basin evolution. Sediment budgeting differs from place to place. Unless the surface changes are related to deep subsurface 'controls', the futuristic extrapolation of the pattern of accommodation space generation and the resident time of rivers in different locations is difficult to predict. To achieve this goal multiscale interrelationship must be known. What is the best way to do this?
First you need to categorize basins according to whether they have rivers that run through them and exit to oceans, or whether they are closed, and the water and
materials enter, but the water exits by evaporation or by subsurface movement.
Basins in conjunction with parallel Mountain ranges are lateral compression
wave forms. The mountains move upward and are vertically unconstrained,
but the downward movement of the basins is vertically constrained by the
crustal layers below. The result is taller mountains and shallower basins.
Rivers remove material from the basin, while mountains feed material to the basin.
The closed basins of the Western United States are an easier study in that the
material remains in an essentially closed system. The oldest basins and shortest
mountain ranges are near the western coast of the US. The younger basins,
and taller mountains are farther eastward into the continent. The basins formed by
a sequence or " block roll overs" from west to east over the last 60 million years.
They are still forming in western Colorado along the Western Slope.
There is thus a sequential " snapshot " of basins formations in the western US.
between California and Colorado, without the complicating problems of
material removal by rivers in some of the basins.
Thank you Michael for your practical suggestions regarding classification of basins in the context of closed and open types. Presently, I am dealing with an open type basin. From a few seismic sections across the valley, we have got a general first order idea about the nature of accommodation space variability in the last 15 Ma or so, how some of the particular sites in the fore-deep areas behaved differently. If it is assumed that the first order changes will have similar type of continuation; we are not so sure about the higher order changes. From the surface observations of the fluvial dynamics, we suspect certain changes in the historical scale which are at places different from the first order changes. These shallow subsurface changes are not possible to identify from the seismic sections. Can you suggest means to verify what we suspect?
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