Page 28 - Studia Universitatis Hereditati, vol 13(2) (2025)

Core JAZ 2 Chronology ments from Lošinj Channel. The opening of
Through units 1 to 7, 23 to 140 cm depth in core, the channel should have had an influence on
signal intensities progess with depth from 8.73 the sedimentary record in Osor Bay. The shal-
x 10 to 1.53 x 10 counts, spiking to 4.88 x 10 4 low south side of the channel, where the mod-
3
4
counts at the base of unit 7, at 142 cm depth in ern harbour is located, is unsuitable for the de-
core (table 4). OSL intensities are more heterog- tection of environmental and human-induced
enous through unit 8, fluctuating around 7.90– changes because of dredging activities over
7.41 x 10 counts. Across the unit 8–9 boundary, time and the lack of stratification of cultural
4
there is a step-change in intensities from < 7.4 x layers.
4
10 to > 1.5 x105 counts, coinciding with the tran- Osor Bay Prior to 5.5 cal ky BP (3500 cal BC)
sition from marine to terrestrial sediments. The
aim was to date marine transgression, so samples In marine environments, organic carbon
28 were taken either side of this bounday at 142 cm (TOC) and C/N are generally considered
depth in core (base of marine sequence) and 171 proxies for the relative contribution of terres-
studia universitatis hereditati, letnik 13 (2025), številka 2 / volume 13 (2025), number 2
cm depth (top of terrestrial sequence). Table 4 trial vs. marine organic matter and shifts in pri-
and table 5 list the palaeodoses and environmen- mary productivity. Ratio of total organic car-
tal dose rates for these samples, together with the bon and total nitrogen (C/N) has been largely
corresponding depositional ages. Further details used discriminate different origins related with
are provided in Appendix. sediment organic matter. Generally, the value
of C/N ratio for organic matter of marine de-
rived organic matter is less than 7, organic mat-
Discussion ter of soil has a ratio 8–20, and the ratio that
Geological Perspective on Osor Bay and Lošinj exceeds 20 is characteristic for organic mat-
Channel ter of terrigenous origin (Meyers, 1994). A low
The analysis of coastal marine sedimentary re- C/N ratio (<8) is found in the marine sedi-
cords can be used to assess the impact of human ments in the core OSOR 2 in the sediment suc-
intervention over time on the surrounding en- cession from the base of the core to a depth of
vironments. High-resolution land and bathym- 200 cm, three centimetres below the dated in-
etric maps were produced by merging airborne terval at 195–197 cm (5.6–5.3 ky cal BP / 3672–
laser scanning (ALS) and high-resolution multi- 3364 cal BC). The sediment geochemistry and
beam sonar data, providing a holistic interpreta- lithology (changes in grain size) indicate sta-
tion of the geomorphology of the town of Osor ble consistent hydrodynamics and the increase
and its surroundings. of carbonate content and decrease of insoluble
The core OSOR 2 was cored at a depth of residuum suggesting a low contribution of ter-
30 m on a gentle shoreface slope close to town rigenous soil input/washout from the land sur-
of Osor but also close to the artificial channel, face. The concentration of organic carbon and
that connects Osor Bay with Lošinj Channel. the C/N ratio correspond to those in the Hol-
The total sediment succession at the coring lo- ocene marine sediments of Lošinj Channel
cation is approx. 3.5 m thick, and the core pene- (TOC < 1.5% and C/N < 10) (Brunović et al.
trated 2.9 m of the sediment succession. The lo- 2020).
cation of the core was chosen to allow access to The base of the core did not reach the car-
an undisturbed sedimentary succession, which bonate bedrock and according to the relative
could record events related to the Osor site, sea level data from Brunović et al. (2020) for
but also to detect possible changes in the sedi- Lošinj Channel the shoreline, 30 m below the
ment records related to the construction of the present sea level was attained at approx. 9.0 cal
channel and the influx and transport of sedi- ky BP. This would indicate that the sediments