Page 116 - Physical Principles of Sedimentary Basin Analysis

98 Burial histories

= N, η = 0 (basin surface)
N
i

η i

i+1 (horizon)
layer i, thickness Δζ i
i (horizon)

ζ i

i=1, ζ =0 (basement boundary)
1
Figure 5.3. The ζ-coordinate (ζ i ) of each horizon, the ζ-depth (η i ) of each horizon and the net layer
thickness ζ i .

We will now look at how net layer thicknesses can be initialized in order to reproduce the
present-day formation thicknesses.
The net thicknesses can be obtained from the observed layer thicknesses starting from
the basin surface by processing layer by layer. The real depth from the basin surface down
to horizon i is z i . The height from the basement up to horizon i, measured as net sediment,
is ζ i . The horizons are numbered starting from the basement (i = 1) up to the basin surface
(i = N). The net thickness of each layer is denoted ζ i , and the real (observed) thickness
of each layer is z i = z i+1 − z i , where the lowest layer is i = 1. The top layer is
i = N −1, because there is always one horizon more than there are layers (see Figure 5.3).
The ζ-coordinates of the horizons are related as follows to the net layer thicknesses:
ζ i+1 = ζ i + ζ i , (5.7)

and using that ζ 1 = 0weget
i−1

ζ i = ζ k . (5.8)
k=1
The ζ-depth (the net depth) from the basin surface down to a horizon is denoted η i , and we
have
η i = η i+1 + ζ i , (5.9)

and using that η N = 0weget
N−1

η i = ζ k . (5.10)
k=i