Dewatering Structure in Trench T1
Kanari et al. (2020) report that Trench T1,
excavated in the
Elat Sabkha, revealed
liquefaction
deformation but no visible
fault trace. The uppermost Unit A is
disturbed by modern agriculture, like the
plow furrows seen in Trench T3. Beneath it lies Unit B,
a sand unit with no sharp boundary from the
disturbed soil above, followed by Unit C, a
laminated sequence of alternating silt and clay.
Below these, Unit D contains interbedded
medium-grained sand with
ripple laminations,
coarse sand lenses, and very fine sand.
Kanari et al. (2020) identify in Unit D clear
evidence of
fluid escape structures,
including contorted and disrupted beds and
ball-and-pillar structures. These features are
interpreted as evidence for a
dewatering structure formed by earthquake-
induced liquefaction rather than surface faulting.
Kanari et al. (2020) note that the
liquefaction deformation in Unit D is capped by the flat-lying
laminated sediment of Unit C. Because Unit C was
deposited after the deformation, its
radiocarbon date
provides a
terminus ante quem for the liquefaction
feature. Two
charcoal samples from the same location in Unit C (ET02)
yielded ages of 690 ± 25 and
675 ± 25,
calibrated to 1269–1389 CE.
Kanari et al. (2020) therefore conclude that
the dewatering structure formed sometime before
the late 13th to late 14th centuries, during an
earthquake that produced strong enough shaking to
mobilize
saturated sand but did not leave an
identified
surface rupture in Trench T1.
Kanari et al. (2020:12–14) suggest that this
T1
paleoliquefaction
may record the
1212 CE earthquake, since no surface rupture
attributable to that event was recognized in the
T3 trench and the T1 liquefaction occurred before
1269–1389 CE. At the same time, they note that it
could instead be the same event as E1, which they
correlate with the
1068 CE earthquake, or another event within
that time window. Thus, the dewatering structure
in Trench T1 is best interpreted as evidence for
strong seismic shaking in the Elat Sabkha before
1269–1389 CE, probably representing either the
same earthquake as E1 or a different event such as
1212 CE, but without enough stratigraphic control
to distinguish between those alternatives.
