694
Chapter 13 Diagenesis
DIAGENESIS OF KEUPER SANDSTONES, PARIS BASIN
a GEOLOGICAL MAP
INCREASING SALINITY
OF PORE FLUIDS
C PORE FLUID MIXING
KEUPER BRINES
1st MIXING
(METEORIC W . +
RESIDUAL HALlTE- ____
1
SATURATED BRINEI
~ 0
-_ - - - - - - - - - - ~ -1
... - -
/
//'
-2
I
DOLOCRETE, SILICA,
PALEOKARST /
~ -3
,/~
~ -4
INITIAL
/~
0
KEUPER
~ ~
J: -5
/
b GEOHISTORY ANALYSIS
TERTIARY
1st FLUID MIXING
I
(+ SALINE BRINE I
t-1
a..
UJ
o
CARBONATE
CEMENTS
(LOW-Eh SOLUTIONSI,
PRECIP . OF K-FELDSPAR,
ALBITE , SOME ANHYDRITE,
AND VARIOUS SULFIDES
2
2nd FLUID MIXING
(+ METEORIC W .I
250
200
150
100
TIME (Mal
50
o
CHLORIDE MASS BALANCE
PORE W . /
0 -6
I
"
~
I
~
'0 -7
~
1,/
k
-8+----.--......,.....---'Z.-?llll4--~
o
BASINAL BRINES
20
40
60
MIXING (%1
80
100
METEROIC WATER
Fig. 13.26. Diagenesis of Upper Triassic (Keuper)
sandstones in Paris Basin. a Geological map showing
outcropping basement and Triassic strata along the
margin of the present-day structural basin. An eastem source delivered saline brine and a southem
source meteoric water to the basin center (study
area). The present-day pore water salinity increases
from the southem basin margin via the basin center
to the eastem margin. b Geohistory of Keuper sandstones, phases of fluid mixing, and cement succession. c Pore fluid mixing, derived from oxygen isotopes and chloride mass balance, controlling main
phases in the diagenetic evolution. (After Spöt! et al.
1993, simplified)