tivity on the carmel faul

Seismic events in Denya Cave
Broken speleothems from Denya Cave yielded break ages that seemed to cluster at
specific times (e.g. ~10-12ka, ~20-24ka, ~29-32ka, ~37-40ka etc. see Table 4 and Figs,
17,18). This indicates that the ages are not random and that certain events affected the
whole cave simultaneously. When considering seismite types, each age cluster is also
classified according to its credibility as a precise indicator of a seismic event.
Single sample dating was not possible for Denya Cave seismites and therefore criteria
for creating sample age clusters through three-dimensional isochron plots were
established, yielding a corrected age for all seismite samples of the same age. This in turn,
established statistical means to discern ages of seismic events, which caused damage in
Denya Cave. Criteria for viable isochrons are based on morphological, special and
chemical factors. Seismic events discerned from Denya Cave seismites, using all
aforementioned criteria and three dimensional isochron plots are: 5.03±0.87ka,
10.42±0.69ka, 20.8±3.0ka, 29.1±3.3, 38.0±2.7ka, 57.9±5.2ka, 137±29ka, 147.6±5.4ka
and 160±45ka (Figs. 38, 39).
4.2.2 Isochron age cluster dating
As mentioned above, all seismite samples that plotted on isochron lines were used for
age calculations. In this study the criteria for establishing a reasonable isochron (see ch.
3.3-Age cluster dating) encompass not only geochemical criteria, but also take into
account structural features within the cave and stratigraphic considerations in the
speleothem sample laminae.
Table 7 shows that calculations using isochrons give average ages, causing some
samples to appear older, whereas a single correction would always cause them to be
younger (e.g. correction factor 1.8 ; Table 7). Essentially this means that the ages of
sample clusters are only significant when the samples are considered as a group. Since the
sampling technique is not as accurate as the actual results from the MC-ICP-MS, it seems
reasonable that any age of a seismic event obtained from this kind of research would
result from averaging individual sample ages.
When using three dimensional isochron calculations all samples are considered, even
those otherwise discarded because of their high detrital content. Those samples add to the
number of samples included in the average and yield more accurate ages because they
better constrain the isochron line.
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