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dynamic interplay between numerous paralic
subenvironments during deposition. The sedimen-
tary architecture reflects both the basinal setting
and the changes in relative sea-level within the
large shallow marine embayment that existed in
Jameson Land in the Early Jurassic.
The structural behaviour of the Jameson
Land Basin during Early Jurassic was of critical
importance for the sediment infill of the basin.
The Devonian to Late Jurassic sedimentary strata
in Jameson Land represent a complex stack of
superimposed basin infill successions represent-
ing successive evolving structural conditions. As
emphasised above, no rift-faults are recognised to
be associated with the structural and depositional
architecture of the Neill Klinter Group. The onlap
of Jurassic strata on Precambrian crystalline base-
ment in Liverpool Land to the east supports the
view that the Neill Klinter Group was deposited
in a sag basin. The sag basin may have formed in
response to thermal cooling subsequent to the
Triassic rifting, similar to the Early Jurassic basins
located on the Norwegian continental shelf (Roberts
et al
., 2009).
Between phases of crustal extension, the
northern Pangean plate experienced regional
changes in sea-level, as documented by T-R
sequences in Triassic to Early Cretaceous rocks
of the Canadian and Fennoscandian Arctic
(Embry, 1989; Johannessen & Embry, 1989; Mørk
et al
., 1989; Riis
et al
., 2008; Midtkandal &
Nystuen, 2009; Glørstad-Clark
et al
., 2010). The
relative sea-level changes that controlled the
sequence stratigraphic development of the Neill
Klinter Group were probably related to regional
vertical lithosphere plate movements associated
with processes in the lower crust or/and the man-
tle causing epeirogenic crustal movements and
may have been combined with local differential
movements along old structural lineaments within
Jameson Land.
Changes in relative sea-level are reflected in the
Neill Klinter Group by basinward-stepping and
landward-stepping depositional architectural ele-
ments comprising the lower and upper strati-
graphic compartments. The lower stratigraphic
compartment of the Neill Klinter Group formed
as an overall prograding wave- to tide-influenced
deltaic depositional system and the upper strati-
graphic compartment as an overall retrograding
series of stacked tide-dominated incised valley
successions and wave-dominated delta deposi-
tional systems (Figs 7, 14 and 15).
Incised valleys and their bounding
unconformities of the Neill Klinter Group
Due to the general high sand content in the Neill
Klinter Group, identification of key stratal sur-
faces depends on the interpretation of deposi-
tional facies and environment. This study has
benefitted much from the previous studies by
Dam & Surlyk (1995, 1998), in particular their dis-
cussion of criteria that can be used to define key
sequence stratigraphic surfaces. However, Dam &
Surlyk (1995, p. 489) concluded that “major
unconformities associated with significant valley
incision have not been observed”.
One main, and new, result of this study is the
identification of three major incised valley sys-
tems. The base of the valley systems is represented
by the combined subaerial unconformities and
transgressive surfaces (SU/TS) that separate regres-
sive elements, proximal or distal, from overlying
transgressive elements. The lithological and strati-
graphical character of conglomerate deposits rest-
ing on these unconformities has been of critical
significance for their recognition. The mixture of
extrabasinal clasts with marine body fossils was
formed when clasts introduced to the basin by
fluvial or/and debris-flow transport were later
reworked by tidal currents that supplied the marine
fossil fragments. Marine body fossils may also have
originated from the substrate incised by the rivers.
From our database, it is not possible to draw
any definite conclusion about the lateral extent of
the subaerial erosional unconformities beneath
the incised valleys. However, the cross-sectional
dimensions of the unconformities in the eastern
Jameson Land outcrop belt indicate that the inci-
sions represent erosional features that may have
affected large parts of the Jameson Land Basin. In
basinward direction towards the west, the incised
valleys, along their respective stratigraphical posi-
tions, may have coalesced and formed regional
subaerial unconformities on a low-gradient ramp
slope, covered by thin gravel and sand sheets.
Several examples of such extensive subaerial
unconformities covered with fluvial deposits are
referred to by Posamentier & Allen (1999, p. 69).
The unconformity beneath the Lower Cretaceous
Helvetiafjellet Formation in Spitsbergen is another
example (Midtkandal & Nystuen, 2009) and simi-
lar regional unconformities have been suggested
to be present within the marginal marine to open
marine Triassic succession in the Barents Sea (Riis
et al
., 2008; Glørstad-Clark
et al
., 2010).
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