Page 25 - Studia Universitatis Hereditati, vol 13(2) (2025)

and lithogenic limestone grains, which were re-
moved before the PSA by laser diffraction. The
most abrupt change in the grain-size distribu-
tion is noted in the sediments at depths of 185
and 200 cm (fig. 9). This sedimentary succession
is characterized by silt and clay fractions and the
absence of sand. The oldest sediments below this
abrupt change show a uniform grain size distri-
bution with approx. 60% of sand and 40% silt.
These silty sands indicate high hydrodynamics
as the core is located close to shore (shoreface)
while the finer fractions were transported to the
more proximal environments (to be proved in 25
cores OSOR 1 and OSOR 3).

Organic Carbon and Nitrogen
Organic carbon content (TOC) is generally be-
low 1.0% and TN below 0.1% in the basal section
of the sedimentary succession up to the depth of Dip Your Finger in the Sea...
190 cm. This section is characterised by the uni-
form low content of TOC and TN and was de-
lineated as geochemical Zone 1 (table 2, fig. 10).
Zone two shows a gradual increase in (TOC)
peaking at the 70 cm to 6.7% (Zone 3) and then
abruptly dropping below 3% (zone 3) to the top
of the core. Nitrogen concentrations peaked in
the interval between 155 and 100 cm, and do not
follow the distribution of TOC, although the
general distribution shows the highest TN in
Zone 2 and a small increase in concentrations
in the topmost samples of zone 3. The difference
in the distribution of N in Zone 2 enabled us to
divide Zone 2 into Subzone 21 (from 190 to 120
cm) and Subzone 22 (from 120 to 190 cm).

Table 2: Mean Values of TOC and TN Concentrations,
Inorganic Carbon (TIC) and Insoluble Residuum (%)
Figure 9: Particle Size Distribution (particle diameter in and Subdivision of Core OSOR 2 into Geochemical
mm) in Core OSOR 2 (elaborated by Croatian Geologi- Zones (elaborated by Croatian Geological Survey, 2025)
cal Survey, 2025)
Mean
The sand content varies from 0.03 to 85.62% Zone N% insoluble res.% TOC% INC%
(average 50.74%) and the silt from 14.4 to 89.35% 1 0.06 32.73 0.28 8.39
(average 47.08%), while the clay content rang- 2 0.20 32.80 2.87 8.11
es from 0.09 to 10.63% (average 2.18%) (table
1). In the silt fraction, coarse silts prevail. The 3 0.14 30.13 3.04 8.22
gravel fraction is comprised of marine molluscs Average 0.14 32.17 2.02 8.23