Jökull - 01.01.2012, Page 124

A. Schomacker et al.
Figure 8. Section 2 in a Little Ice Age marginal moraine ridge at Sólheimajökull. The lower panel illustrates
the composition of the moraine and a simple model of formation. The small box to the left of the persons in
the lower panel indicates the sample location of the organic material. DmC(m2)1: Diamict, massive, coarse-
grained, sandy-gravelly, matrix supported with moderate clast content, loose and not compacted. DmM(m3)3:
Diamict, massive, medium-grained, silty-sandy, matrix-supported, clast-rich, firm and difficult to excavate.
Modified from Krüger et al., 2010. – Snið í jökulgarð frá Litlu-ísöld. Neðri myndin sýnir samsetningu garðsins
og myndun. Litli ferningurinn til vinstri við teiknuðu manneskjurnar á neðri myndinni sýnir hvar sýni til ald-
ursgreininga var tekið í aflöguðu mólagi.
the till slab, small-scale deformation was observed in
layers of sand, silt, and organic material. The top
layer of the backslope, crest, and the foreslope, and
the space beneath the dipping till slab, consists of a
coarse-grained, matrix-supported, loose diamict with
moderate amount of angular to sub-rounded, striated
clasts. This diamict is interpreted as melt-out till (Paul
and Eyles, 1990; Krüger and Kjær, 1999; Krüger et
al., 2010).
The architecture, sedimentology, and the saw-
tooth morphology of the moraine ridge indicate that
it was formed along an advancing and laterally ex-
tending ice margin by a combination of thrusting and
dumping (Krüger et al., 2010). The architecture of
section 2 implies that pre-existing basal till was de-
tached and shoved up during the advance to form
the moraine ridge. Simultaneously, layers of sand,
silt, and organic material were deformed, and debris
melted out of the base and was dumped off the ice
front to form the loose diamict on top. Hence, the de-
formed organic layer observed beneath the dipping till
slab predates the formation of the moraine ridge.
Datings
Two samples of organic material were collected from
the organic layer beneath the moraine ridge in section
2 and submitted for 14C dating (Table 3). The sampled
material is moss which was most likely deposited in
ponds or peat bogs. The samples yielded ages of AD
1512 and AD 1539 providing maximum ages of the
moraine. This indicates that the organic material was
122 JÖKULL No. 62, 2012