Tectonic control on sedimentation, erosion and redeposition of Upper Jurassic sandstones, Central Graben, North Sea - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 487

Table 1. Type A, B and C tectono-sedimentary settings with a number of ield examples.

Tectono-Sedimentary Setting Example Fields / Discoveries

Type A: Hanging Wall Trap Door Setting Flora Field (Hayward et al ., 2003)

Angus Field (Hall, 1992; Spathopoulos et al ., 2000)
NO-2/4-14 Discovery (Mjelde, 1991; Jones et al ., 2013)

Type B: Reactivated Pod Setting Elgin-Franklin Field (Lasocki et al ., 1999)

Fulmar Field (Johnson et al ., 1986)
Clyde Field (Stevens & Wallis, 1991)
Jacqui / Jessica (UK 30/13-3, UK 30/13-7)

Type C: Interpod Setting Kittiwake Field (Wakefield et al ., 1993)

Durward Field, UK 21/16 (Stewart et al ., 1999)
Dauntless Field, UK 21/11 (Stewart et al ., 1999)
Ula Field (Brown et al ., 1992)
Gyda Field (Spencer et al ., 1986)
Nemo discovery, NO-7/7-2

trends are supported by well data, whereas the
extent of deep basin deposits remains sometimes
conceptual because these regions are less cali-
brated by wells. Turbidite deposition is largely
absent, apart from the shallow basin area around
Jacqui and east of Puffin. As an introduction to the
complex relationships between structure and sed-
imentation observed in the Central Graben, the
following sections combine previous observations
of structural setting with those of depositional
controls in order to define and describe several
types of tectono-sedimentary setting (A, B and C).
Practical applications are seen in being able to
identify different styles of deposition occurring in
different structural settings, e.g. correct applica-
tion of analogies; reservoir prognosis based on
structural setting. A number of published exam-
ples of fields or discoveries within Upper Jurassic
sandstones are listed in Table 1 and grouped
according to their type of tectono-sedimentary
setting.

and well documented in the northern Viking
Graben area (e.g. Ravnås et al ., 2000), but are less
common in the Central Graben where the pres-
ence of Zechstein salt and Triassic minibasin
development generally creates a more complex
structural setting.

Type B: Tectono-sedimentary setting

The Type B tectono-sedimentary setting occurred
when Jurassic sediment was able to accumulate
within the same minibasin structures that have
already accommodated Triassic deposition. In such
settings, accommodation space creation for Jurassic
deposition remained significant and thick Jurassic
sandstone successions were developed immedi-
ately overlying thick Triassic deposits. This type of
setting typically occurs within the Central Graben
rift where salt was typically up to 2 km thick. Here,
minibasins continued to develop and ground at a
late stage in the Jurassic (Stewart & Clark, 1999).
Examples of thick Upper Jurassic accumula-
tions deposited in Type B setting include the
Fulmar Formation of Fulmar Field (Johnson
et al ., 1986) and the Franklin Sandstone of Elgin-
Franklin Field (Lasocki et al ., 1999) which host
some of the most important hydrocarbon accu-
mulations of the Central Graben. The Fulmar
(Fig. 10) and Elgin-Franklin fields also display
reworking of previously deposited shoreface
sandstones as turbidite sandstone to areas around
the margins of the collapsing pod, as demon-
strated in correlations of the Fulmar Field made
by Kuhn et al . (2003). It should be noted that a
Type B setting can evolve into a Type A setting.
This is the case for the Fulmar Field where there
exist elements of both settings.

Type A: Tectono-sedimentary setting

Where major faults caused accumulation of Upper
Jurassic shoreface sandstones directly over a
hangingwall trap door, they produced what is
here termed a Type A tectono-sedimentary setting
(Fig. 9). The approximate locations of a few major
Rotliegend-offsetting faults are shown in Fig. 8,
since they influenced Upper Jurassic deposition.
The movement of major Rotliegend fault blocks,
and salt migration, played a fundamental role in
developing the landscape over which Middle
Jurassic fluvial systems and transgressive Upper
Jurassic shoreface sandstones were deposited.
Pure trap door settings of this type are abundant