Evidence of sapropel S1 formation from Holocene lacustrine sequences in Lake Vrana in Dalmatia (Croatia)

Holocene hydroclimate changes in continental Croatia recorded in speleothem δ13C and δ18O from Nova Grgosova Cave

“…Comparison of NG-3 and NG-7 stalagmites δ 18 O and δ 13 C time series data (c) with (a) Mean Anomaly Index (MAI) derived from Corchia Cave data (Bajo et al, 2016; Regattieri et al, 2014a), (b) north hemisphere insolation and (d) sea surface temperature (SST) reconstructed from the South Adriatic marine core MD 90–917 (Siani et al, 2013). Black rectangles mark sapropelic layer S1 from Vrana Lake divided into two episodes S1a and S1b (Bakrač et al, 2018) and blue rectangles refers to Malo Jezero Lake (Mljet Island) pluvial phase interrupted from about 7.2–7.1 ka (Wunsam et al, 1999). Gray shading represents events discussed in the text: (I) 9.2–8.8 ka, (II) 7.4–7.0 ka, (III) 4.2 ka event.…”

“…Combined palynological and geochemical analysis of lake sediment core from eastern Adriatic Vrana Lake provides evidence of climate changes associated with deposition of sapropel S1. Specifically, two sapropelic layers (S1a and S1b, Figure 7) were identified, separated by a horizon at 7.9–7.4 cal ky BP that corresponds to the drier climate conditions (Bakrač et al, 2018). Similarly, a pluvial period reconstructed from eastern Adriatic former lake (presently sea bay) Malo jezero (Mljet Island) lasted from 8.4 to 6 ka, but apparently was interrupted by a drier episode from about 7.2 to 7.1 ka (Wunsam et al, 1999).…”

“…Additionally, high d-excess values indicate increased evaporation of the Mediterranean caused by inflow of cold and dry continental air (Bladé et al, 2012) and further intensified by strong winter winds, for example, bora wind in the Adriatic (Davolio et al, 2017). Meanwhile, the lower spring and summer (Fohlmeister et al, 2012a), BUN -Bunker Cave (Fohlmeister et al, 2012b), KAT -Katerloch Cave (Boch et al, 2009), ERN -Grotta di Ernesto Cave (Scholz et al, 2012), COR -Corchia Cave (Zanchetta et al, 2007), CV -Cueva Victoria Cave (Budsky et al, 2019), ASC -Ascunsă (Drăguşin et al, 2014), SPD -Strašna peć Cave on Dugi otok Island (Lončar et al, 2019), MLJ -Mala špilja Cave on Mljet Island (Lončar et al, 2017), and Malo jezero Lake sediment (Wunsam et al, 1999), VRA -Vrana Lake sediment (Bakrač et al, 2018) and marine core MD 90-917 (Combourieu-Nebout et al, 2013); (b) cave survey with marked speleothem (red dots and IDs) and water (W) sampling sites (according to Caving Club Samobor (Surić et al, 2018)); (c) massive speleothem deposition in the chamber where the stalagmites NG-3 and NG-7 were sampled; (d) climate data: average monthly external air temperature (station Samobor, 1981-2019), precipitation (station Rude, 1991-2019 and the relation between precipitation and potential evapotranspiration) (CMHS, 2020). Water balance (potential evapotranspiration) is calculated using the Thornthwaite evapotranspiration model (McCabe and Markstrom, 2007;Thornthwaite, 1948); (e) δ 2 H-δ 18 O relationship of monthly integrated NG drip water (crosses) and rainwater samples (dots) with associated local meteoric waterline (Surić et al, 2020).…”

“…Constantin et al, 2007; Hercman et al, 2020; Onac et al, 2002; Siklósy et al, 2009; Tămaş et al, 2005), and from the Mediterranean area (Budsky et al, 2019; Bar-Matthews and Ayalon, 2011; Moreno et al, 2017; Psomiadis et al, 2018; Regattieri et al, 2014a, 2019; Scholz et al, 2012; Zanchetta et al, 2007), as well as on regional marine and lake core records (e.g. Bakrač et al, 2018; Ilijanić et al, 2018; Siani et al, 2013; Wunsam et al, 1999) in order to provide better insights into the broad regional changes. Contemporary monitoring of the Nova Grgosova site has revealed influences of both Mediterranean and Atlantic air masses (Surić et al, 2018), whose relative importance probably shifted during glacial-interglacial cycles, given the location of the cave in south central Europe but only 120 km from the Adriatic Sea.…”

Speleothem Records of the Hydroclimate Variability throughout the Last Glacial Cycle from Manita peć Cave (Velebit Mountain, Croatia)

“…The Adriatic Sea, located in the northernmost part of the central Mediterranean, is the contact zone of competing continental European and maritime climate influences. Its eastern Croatian coast, rich in karst features, offers good potential for palaeoenvironmental studies, not only speleothem-based [26][27][28][45][46][47][48][49][50] but also based on other proxies and archives [51][52][53][54][55][56][57]. Palaeoenvironmental studies concerning sea-level changes, conducted on eastern Adriatic submerged speleothems, revealed speleothem deposition during cold climate phases, apparently even during the Last Glacial Maximum (LGM) [45].…”