Molo Member
Nordland Group,
Kai Formation
Eidvin, Bugge & Smelror: The Molo Formation, article
Name
English/ Norwegian
Molo Member/ Mololeddet
Previous names
"Frøyrygg formation" by Askvik & Rokoengen (1985) and "Molo formation" by
Gustavson & Bugge (1995).
Derivatio nominis
Named from the Norwegian word for breakwater (mole).
Original definition
The member is formally described herein.
Lithology
The lithology varies considerably throughout its distribution area. In most well and
boreholes from proximal parts (including type well
6610/3-1),
the unit consists mainly of
red to yellow coloured sand. Some sections also contain well-rounded, rust tinted
pebbles. In some wells glauconitic sand and mica-rich sand are recorded. In the Draugen
Field (Trøndelag Platform), where the distal part is investigated, the unit contains
glauconitic sand, silt and clay (see reference well
6407/9-5).
Thickness
A total thickness of 206 m in the type well is only sampled with five side-wall cores (Fig.
x). In the reference well a total thickness of 117 m is sampled with ditch cutting samples
at ten meters interval (Fig. x). Some short vibro cores are sampled in the Nordland Ridge
area (Fig. x). Close to its northern boundary (block xxxx/x) the unit reaches more than 500
m (Fig. x).
Geographical distribution
The formation extends from the cost off Møre, along the inner Mid Norwegian shelf up to
the Nordland Rigde and Lofoten area.
Type well
Well name
6610/3-1
Location
WGS84 coordinates: 66°55'29.70"N, 10°54'06.28"E
UTM coordinates:
UTM zone:
Drilling operator name
British Petroleum/Saga Petroleum
Completion date
Interval of type section (m)
From 555 m (base) to approximately 349 m (the top is not sampled and logged in the type
well).
Thickness in type well (m)
Approximately 206 m
Reference well
Well name
6407/9-5
Location
WGS84 coordinates: 64°16'42.35" N, 07°44'14.66"E
Drilling operator name
Norske Shell
Boundaries
Lower boundary (basal stratotype)
The lower boundary is recognised by an abrupt change from greyish claystone
of the
Brygge Formation to grey mica-rich sand of the Molo Member. The lower boundary is at
559 m in the type well section. The boundary is marked by a strong negative spike on the
gamma log, and is also shown by a marked positive spike on interval transit time.
Upper boundary (characteristics)
The upper boundary is not sampled and logged in the type well and it is only recognized
on seismic lines.
Lower and upper lower boundaries in reference well sections
In the reference well the lower boundary is recognized by an abrupt change from grayish
claystone to the Brygge Formation to dark (nearly black) glauconitic sand of the Molo
Member. The boundary is further marked by an increase in the gamma ray response and a
decrease in velocity readings.
The upper boundary is recognized by a marked decrease in velocity readings and a slight
decrease in the gamma ray response into the overlying glacio-marine diamicton.
Age
The member is dated as Early Miocene to Late Pliocene (Eidvin et al. in press).
Depositional environment
The member was deposited in a costal shallow marine to prograding deltaic environment,
probably formed in a wave-dominated environment with extensive long-shore drift
(Rokoengen et al. 1995; Bullimore et al. 2005).
Remarks
References
Bullimore, S., Henriksen, S., Liestøl, F.M. & Helland-Hansen, W. 2005. Clinoform
stacking patterns, shelf-edge trajectories and facies associations in Tertiary coastal deltas,
offshore Norway: Implications for the prediction of lithology in prograding systems.
Norwegian Journal of Geology 85, 169-187.
Gustavson, M. & Bugge, T. (1995). Geologisk kart over Norge, berggrunnskart VEGA,
M 1:250 000. Norges Geologiske Undersøkelse.
Rokoengen, K., Rise, L., Bryn, P., Frengstad, B., Gustavsen, B., Nygaard, E. &
Sættem,
J. 1995. Upper Cenozoic stratigraphy on the Mid-Norwegian continental shelf. Norsk
Geologisk Tidsskrift 75, 88-104.
