12.6 Foreland Basins, Molasse
C PROGRADA TlONRETROGRADATION
CYCLES (PR-RG!
AND
TECTO-SED IMENT ARY
UNITS (TSU)
ONlAP
ANGULAR
UNCONFORMITY
617
SW-NE CROSS-SECTION
j
ISOCHRONES
ALL: FAN FLUVIAl
11 ACTIVE
e
CONGLOMERATES
THRUST BELT
DOMINATED BV
CYCLES
TSU CARBONATES SILICICL.
ALL. FAN
FlUVIAL
PG
RG
VARIATION IN SEDIMENT
COMPOSITION
PG
RG
INACTIVE
THRUST BELT
Fig. 12.37. a Composite Ebro fore land basin between
the southem Pyrenees, the Iberian range, and the
Catalan coastal ranges. (Modified after Coney et al.
1996). b Cross sections of Rioja trough, western
Ebro basin, showing onset of overthrusting from both
north and south (Paleocene) and advanced stage of
basin evolution (Miocene). c Schematic cross section
of southern part of foreland basin demonstrating lateral facies change and the interplay between short
episodes of overthrusting and times of reduced tectonic activity. These processes lead to either
prograding, coarsening-upward or retrograding
TECTONIC
ACTIVITY
PG
fining-upward sequences. Note intervals of non-deposition and erosion as weIl as disconformities, offand onlap features along the basin margin. d,e Cartoons displaying periods of siliciclastics-dominated
sediment supply (tectonicaIly quiet) alternating with
periods rich in the supply of calcareous components
(renewed tectonic activity). The presence or lack of
coarse-grained carbonate particles in vertical sections
indicates progradation-retrogradation cycles. (b-e
Modified after MUrloz-Jimtmez and Casa-Sainz
1997)