Channel development in the chalk of the Tor Formation, North Sea: evidence of bottom current activity - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 555

3000

N S

3100

3200

3300

3400

3500

3600

3700

3800

2.5 km

3900

3000

N S

3100

3200

3300

3400

3500

F

3600

3700

Truncation
Onlap
Interpreted limit of the
channel structure

Top Ekofisk Fm
Top Tor Fm

3800

2.5 km

Middle Tor SB

3900

Top Magne Fm
Top Thud Fm
Top Narve Fm
Top Blodøks Fm
Base Hidra Fm

F Fault

Fig. 3. Reflection configuration and terminations within the seismic units of the Chalk Group (cf. stratigraphy in Fig. 2);
note the location of the studied channel.

upper boundary of the Tor Formation (light green
horizon of Figs 3, 5, 6 and 7) and the base of the
Danian clay-rich Ekofisk dense zone.
Biostratigraphic dating of the Tor Formation is
based on nannofossil and microfossil data docu-
mented in well reports, from the cored intervals of
well 2/4-12 (Martsolf, 1994), wells 2/4-A8 and
2/7-4 (Bailey et al ., 1999) and well 2/7-14 (Young &
Yang Logan, 1994). The biostratigraphic dates indi-
cate that the upper sequence is upper Maastrichtian,
corresponding to the UC19 and UC20 nannofossil
zones (Fig. 2) (Bailey et al ., 1999). Biofacies are

dominated by planktonic and benthic foraminifera.
In well 2/7-14, radiolarians have been noted in the
intervals 3278 m to 3290 m and 3308 m to 3310 m.
Ostracods, Inoceramus bivalve fragments and
scaphopods are also present but do not provide
useful biostratigraphic datings.

Seismic evidence of the channel

Seismic amplitude mapping of the top Tor
Formation reflector reveals a distinctive strong
negative amplitude in the region adjacent to wells