Geoscience Reference
In-Depth Information
The Early Jurassic marginal marine Jameson
Land Basin was to the south connected to a rela-
tively narrow and long basin system of the proto-
Norwegian-Greenland Sea. This basin system is
today represented by the tide-influenced and
wave-influenced marine Jurassic succession on
the mid-Norwegian continental shelf (Gjelberg
et al
., 1987; Dalland
et al
., 1988; Skogseid
et al
.,
2000; Brekke
et al
., 2001; Nøttvedt
et al
., 2008;
Mitchell
et al
., 2011).
Ground and aerial photo-mosaics were used to
map large-scale lateral and vertical changes in
texture and structure and the geometry of deposi-
tional units.
DEPOSITIONAL ARCHITECTURE
Key stratigraphic surfaces in the
Neill Klinter Group
The lowest frequency (i.e. higher hierarchy) key
surfaces include three subaerial unconformity sur-
faces (SU), six transgressive surfaces (TS) and five
maximum flooding surfaces (MFS). The SU sur-
faces are extensive, irregular to subhorizontal ero-
sive surfaces overlain by cm-thick to dm-thick
matrix-supported or clast-supported conglomeratic
beds containing extra-basinal quartz pebbles and/or
granules, quartzite and gneiss clasts, coalified wood
and plant debris and marine body-fossil fragments
(Fig. 5A-C). The TS surfaces are extensive, irregular
to subhorizontal surfaces across which a facies of
more proximal character is sharply overlain by
more basinward distal facies (Fig. 5A and D).
Transgressive surfaces are interpreted as marine
ravinement surfaces created by tidal scouring and
coastal onlap. The TS surfaces mostly coincide with
the preceding subaerial unconformities and these
two types of surface together form combined SU/TS
surfaces (Fig. 5A to D). The maximum flooding sur-
faces (MFS) are defined by up to several metres-
thick condensed zones of the most distal lithofacies.
Although the maximum flooding surfaces record
relatively slow transitions from landward to basin-
ward sedimentation, they have been applied as cor-
relative surfaces, in accordance with general
principles of sequence stratigraphic correlation
(Van Wagoner
et al
., 1988; 1990; Posamentier
et al
.,
1988; Posamentier & Allen, 1999; Catuneanu, 2006).
The high frequency (i.e. lower hierarchy) key
surfaces comprise four marine ravinement sur-
faces (MRS) (regressive or transgressive) and
seven flooding surfaces (FS). These surfaces
define local basinward or landward shifts in facies
belts (Fig. 5A, E and F). Correlatability of key sur-
faces varies from a few kilometres to more than
several tens of kilometres.
METHODOLOGY AND TERMINOLOGY
The study was carried out in two outcrop areas
along the eastern coast of Jameson Land (Fig. 1).
The primary dataset consists of 32 measured
sections produced in 8 localities along the over
100 km N-S oriented transect (Fig. 4). In addition,
selected sections from Dam & Surlyk (1998) were
consulted. The measured sections are 30 to 300 m
thick and record grain size, sedimentary struc-
tures, palaeocurrent directions (measured from
dune foresets), nature of bedding, bedding contacts,
lateral variability, trace fossil assemblages and
degree of bioturbation.
In this study, the Neill Klinter Group is divided
into two stratigraphical compartments (Fig. 2)
composed in total of eight allostratigraphic units
(North American Commission on Stratigraphic
Nomenclature, 1983, p. 865; Bhattacharya, 2001).
Allostratigraphic units are defined on the basis of
observed bounding discontinuities representing
changes in relative sea-level, or changes in the ratio
between rate in creation of accommodation space
versus
rate of sediment supply (A/S). Each allostrati-
graphic unit is formed by a certain set of architectural
elements (described below) that in a specific manner
characterise particular stages in the depositional his-
tory of the Neill Klinter Group. Each architectural
element consists of one or more facies associations
and is bounded by key stratal surfaces reflecting bas-
inward or landward shifts of the palaeo-shoreline.
Key stratigraphic surfaces, architectural ele-
ments and their organisation in allostratigraphic
units form the descriptive database for a concep-
tual depositional model and for a transgressive-
regressive (T-R) sequence stratigraphic framework
of the Neill Klinter Group. A 105 km-long correla-
tion profile was formed by combining new field
data, published data and photo-mosaics to
illustrate the T-R sequence stratigraphic framework
for the Neill Klinter Group (discussed below).
Facies and facies associations
A total of 14 lithofacies (labelled F1 to F11) have
been defined in the Neill Klinter Group (Table 1).
The main lithofacies are sand-dominated and
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