Naslov
Tufa growth at the Zrmanja and the Krupa rivers and possibilities for palaeoclimate reconstruction, Croatia

Autori
Barešić, Jadranka ; Sironić, Andreja ; Borković, Damir ; Horvatinčić, Nada ; Krajcar Bronić, Ines ; Faivre, Sanja ; Buzjak, Nenad ; Veverec, Iva

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
5th regional meetimg on Quaternary geology dedicated to geohazards and Final conference of the LoLADRIA project "Submerged Pleistocene landscapes of the Adriatic Sea" : abstracts / Marjanac, Ljerka - Zagreb : Hrvatska akademija znanosti i umjetnosti (HAZU), 2017, 3-3

ISBN
978-953-347-190-7

Skup
5th regional meetimg on Quaternary geology dedicated to geohazards

Mjesto i datum
Starigrad, Hrvatska, 09.11.2017. - 10.11.2017

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
tufa ; Zrmanja river ; Krupa river ; radiocarbon dating

Sažetak
Tufa deposits along the two karst rivers were dated with the aim of reconstructing palaeoenvironment and palaeoclimate settings from fresh-water carbonates. The Zrmanja river (69 km long) is located in the Dinaric karst, the NW Dalmatian plateau, and flows into the Adriatic Sea. The Krupa river is a tributary of the Zrmanja river. Both rivers are characterized by calcium carbonate precipitation in water streams forming tufa barriers. This work presents analyses of of the Zrmanja river physico-chemical parameters important for authigenic carbonate precipitation in form of tufa, as well as isotopic analyses of dissolved inorganic carbon (DIC) and fresh and old tufa deposits. Water samples were taken at 9 locations along the Zrmanja river and at 3 locations along the Krupa river including springs of both rivers and the confluence of the Krupa to the Zrmanja river. Measured values of temperature, pH, and concentrations of carbonate and calcium ions revealed conditions favourable for tufa precipitation in a downstream flow of both rivers (ISAT, saturation index of CaCO3 ≈5). Tufa does not precipitate at springs where ISAT <1. Radiocarbon activities (a14C) of dissolved inorganic carbon (a14CDIC) from the Zrmanja river showed increase from ≈78 pMC at springs to ≈90 pMC downstream, and δ13CDIC values showed no trend (-12.8 – (-11.4) ‰). On the contrary, δ13CDIC from Krupa river showed slight downstream increase (-14.2 – (-13.3) ‰), while a14CDIC remained almost constant (≈88 pMC). Old tufa deposits were found at 6 locations at canyons of both rivers. The old tufa a14C values showed the range from 85 pMC (≈1 m above water level) to almost 0 pMC, older than 50, 000 BP (≈30 m above water level). Two samples from the oldest tufa deposits were dated by the U-Th method and the obtained age was ≈130, 000 y in both cases. The recent tufa a14C value sampled from stream was 83 pMC, very similar to a14CDIC from same location (Gazin Kuk, 87 pMC) and could be regarded as initial radiocarbon activity of tufa. Results of 14C dating of tufa deposits obtained by two measurement techniques (benzene synthesis – liquid scintillation counting – LSC-B, and graphite synthesis – accelerator mass spectrometry – AMS) showed similar results for dates <12, 000 BP. Tufa deposits which were dated to >25, 000 BP by LSC-B method did not show satisfying concordance with results obtained by AMS technique indicating very heterogeneous precipitation of tufa deposits. Nevertheless, acceptable results obtained from 14C and U-Th dating indicate that tufa precipitated during the Holocene and the interglacial stage MIS5.

Izvorni jezik
Engleski

Znanstvena područja
Kemija, Interdisciplinarne prirodne znanosti, Geografija

POVEZANOST RADA