Climatic and tectonic controls on Triassic dryland terminal fluvial system architecture, central North Sea - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 34

(A)

Perennial to intermittent streams

Overbank shrubland
vegetation

Calcic palaeosols

(B)

Alternating terminal splay
and lacustrine delta

Variably vegetated to desiccated
distal reaches

Sabkha alternating with lacustrine
shales

Fig. 12. Conceptual depositional model for the Middle and Late Triassic in the central North Sea. (A) Proximal facies were
typically dominated by sand-prone accretionary bar deposits from large, intermittent river systems flanked by well drained
shrubland floodplain. (B) Distal regions were characterised by interbedded floodplain, lacustrine and playa facies
representing conditions of fluctuating desiccation.

may be indicative of the reduced frequency of
sand transporting discharges in the lower reaches
of the Skagerrak Formation terminal systems.
In summary, the general facies composition of
the middle and upper Triassic succession in the
central North Sea is suggestive of a dryland depo-
sitional system which was typically wetter than
that of the lower Triassic (Fig. 12), alternated
between episodic playa desiccation and periods
of deposition along active river courses which
sourced perennial lakes and marshes and supported
a moderately diverse plant and animal population
(McKie & Audretsch, 2005; McKie, 2011).

the south (Mange-Rajetzky, 1995; McKie et al .,
2010; McKie, 2011). There is very little evidence
of northward directed palaeoflow. The extent to
which the Triassic fluvial systems exited the
central North Sea is debatable due to the paucity
of data adjacent to and within the mid-North Sea
High region. However, well data from the north-
ern part of the Dutch sector of the North Sea,
which would be immediately downstream of the
central North Sea fluvial systems, generally shows
limited evidence of major fluvial activity and
typically comprises mud-prone playa (Bunter
Shale and Keuper formations) or marginal marine,
mixed carbonate-clastic sabkha or lagoonal facies
(Muschelkalk Formation). These facies either
represent the distal termination of the central
North Sea systems or, if the mid-North Sea High
region had acted as a physical barrier, then the
systems must have been fully contained within
the central North Sea and terminated within this
region. There is no evidence that the river systems

Terminal character of the Triassic
fluvial systems

The provenance and palaeocurrent data for the
central North Sea fluvial systems are indicative of
lateral drainage from the UK and Fennoscandia,
which converged into an axial drainage towards