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sediments were reworked by waves and longshore
currents in an open water setting, but wave energy
must have been low enough to allow for a wide
diversity of organisms to thrive. The appearance of
mixed brackish-marine palynomorphs (this study)
at locality N2 may indicate locally lower salinity or
lower sedimentation rates in the northern area. The
thinner bedded and extensively bioturbated muddy
sandstone strata in most of the northern localities
suggest generally lower sedimentation rates than
along the southern localities.
In the southern area, the maximum flooding sur-
face MFS5 is represented by a condenced section
formed by the finest-grained distal marine facies
below upward-coarsening units (Fig. 5A). In the
northern area the MFS5 is defined by the top of the
well-cemented bed of fossiliferous hardground
(FA6b; Figs 7 and 13A). The WDDL element is trun-
cated below the SU3/TS6 surface, except at locality
N1 where the WDDL element facies appears to pass
directly into offshore marine mudstone (FA7b) of
the Sortehat Formation (architectural element SORT;
Fig. 7). The area of locality N1 is therefore consid-
ered to be located between two incised valleys.
of coarse sediments on the subaerial unconformity.
This process was accompanied basinward by
regressive ravinement scouring into the under-
lying marine strata (Fig. 13B and E). During the
subsequent rise in relative sea-level, transgressive
ravinement and deposition took place along the
same surface, forming the transgressive ravine-
ment surface (TS6). Hence, the deposits above the
unconformity surface records retrogradational
depositional architecture. In general, the incision
is considered to have been controlled by 1) rate of
decrease in accommodation space; 2) rate of sedi-
mentation; 3) distance from the sediment source;
4) type of underlying substrate; and 5) the energy
system present (fluvial, tides, waves). The com-
bined SU3/TS6 surface defines the lower bound-
ary of the overlying allostratigraphic unit 8, which
also is typified by the presence of incised valleys
(see next section).
Allostratigraphic unit 8
Description: Retrogradational architectural
elements succession - Incised valley system 3
and the Sortehat Formation
Subaerial unconformity SU3 and
transgressive surface TS6
At localities S3 to 6, the sandstone-dominated
allostratigraphic unit 8 is 10 to 50 m thick, at
least 30 km wide and overlies the SU3/TS6 sur-
face (Fig. 7). At locality S3, the allostratigraphic
unit 8 is composed of an up to 10 m thick single
unit of middle to upper shoreface sandstone
facies association (FA4a) with abundant cm-size
to dm-size sideritic concretions and sandy tidal
channel infill facies associations (FA3a, 3b and
3c) (Table 2). North of locality S3, the allostrati-
graphic unit 8 is composed of laterally shifting
sandy tidal channel infill facies associations
(FA3a, 3b and 3c) and large-scale tidal inclined
heterolithic strata facies associations (FA2a and
2b) (Table 2). At locality S5, the allostratigraphic
unit 8 is dominated by tide-influenced sandy
heterolithic delta front facies association (FA5a),
compound heterolithic subtidal dune facies
association (FA3c) and a single laterally contin-
uous bed of tide-influenced heterolithic prodelta
mudstone facies association (FA5b) (Figs 7
and 12B; Table 2). At locality S6, the allostrati-
graphic unit 8 is dominated by sandy tidal chan-
nel infill facies associations (FA3a, 3b and 3c;
Table 2).
No sandstone-dominated allostratigraphic unit
8 is observed at locality N1. At localities N2 to
4, the up to 45 m thick and less than 16 km-wide
Description
The sharp unconformity on top of the shaly WDDL
element sandstones of allostratigraphic unit 7 is
overlain by thin beds of conglomerates containing
extrabasinal pebble-sized quartz clasts, few centi-
metres-long belemnites and marine shell frag-
ments. At localities S3 to 6, field mapping revealed
that the unconformity defines an up to 50 m deep,
irregular and northward-deepening incision (Fig. 7).
The unconformity is not identified at locality N1,
whereas at N2 it is overlain by an up to 10 cm thick
conglomerate bed with angular rip-up mud clasts,
floating rounded gravel to pebble size quartz clasts
and belemnite rostra fragments (Fig. 13E to G),
similar to the conglomerate bed at localities S3 to
6. At locality N2, the incision measures up to 45 m,
decreasing to a few metres along the localities N2
to 4 and disappearing north of N4 (Figs 7 and 13A).
Interpretation: Subaerial unconformity SU3
and transgressive surface TS6
It is interpreted that the incision of SU3 took place
during a fall in relative sea-level that caused flu-
vial erosion into marine deposits and deposition
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