Page 30 - Studia Universitatis Hereditati, vol 13(2) (2025)

best visualised on the diagram in figure 9. The point human signatures on nutrient inputs to
distribution is complex and differs within Zone the coastal area. However, although multiple or-
2. Subzone 21 exhibits a trend of gradual increase ganic matter sources have been identified in nat-
of terrestrial organic carbon into the bay from 5.5 ural coastal sediments, widely used mixing mod-
cal ka BP to 2.2 cal ka BP (3500–200 cal BC). els have only two end-members, terrestrial and
The positive correlation between TOC and N marine sediments (Ogrinc et al. 2005). Future re-
is typical of natural environments and terrestri- search should focus on d15N content of the core
al plants. In Zone 22 (from 2.2 cal ka BP to 1.5 OSOR 2 which could be used to track agricul-
cal ka BP) this correlation does not exist: organic tural and urban point sources. In summary, ter-
carbon is increasing, and nitrogen is decreasing. rigenous material has lower values for d15N and
This is probably a consequence of the large input d13C than estuarine and marine organic mat-
of charcoal from human activities in Osor. Car- ter (Ogrinc et al. 2005). The geochemical change
30 bon and nitrogen associations suggest that an- through the OSOR 2 core reflect a complex his-
thropogenic activity in the Osor area was grad- tory of environmental change generally caused
ually intensifying through Subzone 21 and then by the anthropogenic influence of Osor.
studia universitatis hereditati, letnik 13 (2025), številka 2 / volume 13 (2025), number 2
intensified in amount and peaked after 2.2 cal ka
BP. During this period (Subzone 22), the altered Osor Channel and the Town’s Maritime
C/N signature is possibly a consequence of more Accessibility from Archaeological Perspective
advanced technologies of firing used compared The dating of the opening of the Osor Channel
to the period of Subzone 21 or a change in source for maritime use is an important issue in all ar-
of organic matter. chaeological disputes concerning the maritime
accessibility of Osor. As mentioned in the in-
Environmental Changes in Osor Bay Marine troduction, it is widely accepted that the chan-
Sediments After 270–584 cal AD nel was created by humans during the Iron Age
The geochemical record of Osor Bay marine sed- or Roman period. However, the results obtained
iments dramatically and abruptly changes after during the last two years of research contradict
70 cm (1.7–1.4 cal ky BP/270–584 cal AD), the this archaeology-based interpretation.
source of organic carbon is different than in Sub- Sediment core OSOR 2 has the potential to
zone 22, with a trend indicating a gradual demise serve as a possible sedimentary record for deter-
of dominantly terrestrial derived organic carbon mining the timing of the opening of the Osor
towards primary marine production of organic Channel. However, geochemical and sedimen-
matter (fig. 11). The change in CN ratio indicates tological analyses have not yet succeeded in es-
a progressive change in sources of organic mat- tablishing this event’s precise timing. Material
ter and increased deposition of inorganic carbon transported by currents from the Lošinj Chan-
(carbonates; fig. 10). The lower C/N ratio is most nel shelf area could carry specific fossils (ostra-
probably a consequence of several factors includ- cods and foraminifera) or plant remains from
ing decreased vegetation cover and loss of wood- the marshes on the southern side of the chan-
land surrounding Osor. The depositional envi- nel. Once the correct proxy has been identified,
ronment through this period was less influenced it may be possible to precisely date the opening
by anthropogenic activities although higher nu- of the Osor Channel.
trient loading can be detected in the youngest Current state of research and the gradual in-
sediments indicated by an increase in nitrogen crease in terrestrial organic carbon and the initial
14
content (fig. 10 and fig. 11). Resolving the com- initial C data imply that an increased contribu-
plex system of anthropogenic influence of Osor tion, potentially due to human activities such as
in the future would be through an evaluation of deforestation, may have begun as early as 5621–
the contribution from each source and to pin- 5313 cal BP (3672–3364 cal BC). It is also plausi-