Page 247 - The Geological Interpretation of Well Logs

- FACIES, SEQUENCES AND DEPOSITIONAL ENVIRONMENTS FROM LOGS -
LITH.

3" GAMMA RAY API | SONIC Réit 7
Oo, , , “caliper 100 1590

0 SS
\Y 1 al. g
10m 4 “ y- aR xe
WO
dip 2° ox
N _ Er
20m - 3
bit
size v gep
IWS 7
c15 ma

30m 4 SN UNCONFORMITY a
PEAK 5

Oo OeeeelG a
cc oO

som
Figure 14.19 Anomatous gamma ray peak at an unconformity. The peak corresponds to gap of [5 Ma: its stratigraphic importance
is evident. The radioactivity is probably due to uranium concentrated in phosphatic nodules.

AUNAL
. SHALLOW DENSITY ENV. f
el]e|@] . GAMMA RAY |resisTivITY =| Mason | envs. BREAKS co
e/#)S] =z E Sonte 3 Reig g crcLes SEQUENCES MMENTS
5|z13) 5
° 2 x00} B22 i -

|
w) ic '

5/2 FU deepening bagin sinking?
a3] 2

oS

>
UNCONFORMITY: | _ slight structuration
MAJOR Limit
26 7 =
| progressive
more deepening sea level tise?
marine
LL
<=
= LL FLOODING: =|
3
_ EXTENT? SEQUENCE LIMIT?
« tluvial channel
s FU in core
yg]
6) 3 = co erosion: channel,
<x delta top Isuna
in core

&
- }——4
= u major
\ e della
764 progradalion
LC oe ee MAJOR
PROGRADATION
5
at

&
=z a 4 = | i aur l FLOODING:
8 3 s cv
=
«
8
>
a
5
400m + ist eustatig sea level
a
‘>
2
.
ise
5
MAJOA
SEQUENCE LIMIT
a

Figure 14.20 A completed electrosequence analysis. Lithology, electrofacies and sample data are brought together to give a verti-
cal sequence of depositional environments and an indication of the depositional sequences and major breaks.
*Environments: |, deeper marine; 2, shallow marine; 3, prodelta; 4, delta front; 5, delta top; 6, channel; 7, beach-littoral; 8,
continental; CU = coarsening up, FU = fining up.

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