Sedimentation at the Jurassic–Triassic boundary, south-west Barents Sea: indication of climate change - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 209

uplift concurrent with subsidence and deposition
in the offshore areas including the Hammerfest
Basin. Subsequently, Hendriks (2003) presented
apatite fission track analyses indicative of a con-
temporary phase of Late Triassic to Early Jurassic
uplift in the onshore regions from eastern
Finnmark to the Kola Peninsula, with estimated
2.5 km to 3 km of denudation.
This reported evidence for Late Triassic to Early
Jurassic uplift and erosion in onshore areas to the
south of the Barents Sea basins may link to the
transition to more quartz-rich sandstones above
the Snadd Formation. Such a phase of hinterland
rejuvenation may also have played its part in
introducing much coarser clastic material into the
depositional basins, as recorded from the Tubåen
Formation, in particular. It is also tempting to
relate the inferred reduction in basin subsidence
rate (Fig. 12) to concurrent uplift/denudation in
the onshore area to the south; although a clear
genetic (tectonic) linkage cannot be demonstrated
in this study.
With reference to the North Sea area, it is also
noteworthy that Paul et al . (2009) concluded that
rapid Late Triassic uplift in the Caledonides of
southern Norway accounted for provenance varia-
tions in the Keuper sandstones in Germany.
Similar to Hendriks & Andriessen (2002), Paul et
al . (2009) referred to rift shoulder uplift along the
Atlantic rift system to account for the Late Triassic
to Early Jurassic increase in denudation. These
interpretations support a conclusion that hinter-
land rejuvenation played an important role in
changing depositional trends at the Triassic to
Jurassic boundary on the Norwegian shelf; from
the North Sea to the Barents Sea areas.
Furthermore, the Early Jurassic palaeogeo-
graphic reconstructions of Smelror et al . (2009)
suggest that the western part of the Barents shelf
became shielded from sediment input from the
Uralides and Novaya Zemlya by a major marine
embayment developing in the South Barents and
North Barents basins (Fig. 2), in marked contrast to
the dominant Triassic setting with continuous sed-
iment transport across these basins (Riis et al . 2008;
Smelror et al . 2009). Accordingly, it appears that
the Early Norian marine incursion may eventually
have terminated the supply of sediment from the
south-east across the Barents shelf, thus further
enhancing the petrographical changes induced by
hinterland rejuvenations in Fennoscandia.
Finally, shortening of fluvial transport distances
between the Snadd and Tubåen formations can

also be considered. If the primary source for sandy
sediment in the Snadd Formation is located in the
Uralides to the south-east, sediment transport
over approximately 500 km to 1000 km is required
to supply sediment, for instance, to the Bjarmeland
Platform (Fig. 2; see also Riis et al ., 2008). In con-
trast, direct supply of quartz-rich sediment from
the Caledonides of northern Norway into the
Hammerfest and Nordkapp basins would require
transport distances of approximately 100 km
to 200 km or less. As river sediment typically
becomes finer grained downstream, increasing
sediment supply form Fennoscandia across the
Triassic to Jurassic boundary may have also con-
tributed to an increase in the sandiness and over-
all grain size of the Tubåen Formation, as compared
to the Snadd Formation. If the Fennoscandian
hinterland was subject to additional rejuvenation
during Late Triassic to Early Jurassic times, these
effects (increased sandstone content and coarser
grain sizes) would be amplified even more.

Geographic and temporal climatic variations

Late Triassic climates in the south-west Barents
Sea have been addressed by Hochuli & Vigran
(2010), who examined climatic variations from
palynological records, e.g. in the Nordkapp Basin.
These workers found that the entire post-Early
Carnian interval is characterised by a very warm
climate. Furthermore, an abrupt change from dry
to more humid conditions is recorded at the Early
to Late Carnian boundary (i.e. within the Snadd
Formation). Regional occurrence of coal-bearing
strata in the Late Carnian to Early Norian upper
part of the Snadd Formation, as well as the domi-
nant grey colour of the floodplain deposits, is in
good accordance with a humid climate, as coals
(peat) require water-saturated conditions and high
groundwater level to form (e.g. McCabe, 1984).
Furthermore, the sedimentary successions
described here from the Fruholmen and Tubåen
formations (coal-bearing grey beds in the delta
plain) accords with a humid climate throughout
the Norian to Hettangian stages, thus it may seem
that Late Triassic and Early Jurassic climates were
relatively similar in terms of overall humidity.
However, Bugge et al . (2002) have described red
beds from the upper part of the Snadd Formation
in the Nordkapp Basin; and sporadic red/grey
mottled palaeosols also occur in the Fruholmen
Formation in some cored sections (e.g. well
7226/11-1; Fig. 9). Such red colouration would