Geo log i cal Quar terly, 2005, 49 (2): 185–194 Lateglacial-Mid dle Holo ce ne stable iso tope recor ds in two coeval stalag mite s from the Bihor Mountains, NW Romania Tu dor TÃMAª, Bogdan P. ONAC and Ana-Voica BOJAR Tãmaº T., Onac B. P. and Bojar A.-V. (2005) — Lateglacial-Mid dle Ho lo cene sta ble iso tope re cords in two co eval sta lag mites from the Bihor Mountains , NW Rom ania. Geol. Quart., 49 (2): 185–194. Warszawa. Oxy gen and carbon stable iso tope records of two sta lagm ites from NW Ro mania pro vide a con tinu ous cli matic record be tween 14.8 and 5.6 ka BP. The chronol ogy is estab lishe d by 21 TIMS uranium serie s ages. Uncer tainties in the isotope chro nology range be tween ±20 18 13 and ±100 yr. The d O val ues are pos i tively cor re lated with tem per a ture, whereas d C fluctu a tions suggest changes in soil CO2 pro duc- tion. Lateglacial depo sition of both stalag m ites started at ~14.8 ka BP. The d18O re cords sub sequently show a slow decline in tem pera - tures until 12.6 ka BP. Three warmer pe riods with incre ased soil produc tiv ity occurr ed at 14.5–13.9 ka BP, 13.6–13.2 ka BP, and 12.9–12.6 ka BP. Lower d18O and high d13C values betwee n 12.6 and 11.4 (11.7) ka BP in dicate a cold and dry clim ate dur ing the Youn - ger Dryas (GS-1). Dur ing the Early Ho lo cene, three short cold inter vals are marked on the d18O profiles at 11.0–10.6, 10.5–10.2 and 9.4–9.1 ka BP. For the rem ainder of the Holo cene sequence , the d18O records show less vari a tion be tween 9 and 7.8 ka BP and grad ual warm ing from 7.6–5.6 ka BP. The speleothem records corre late with the Greenland ice core re cords and with other prox ies throughout Europe and the North Atlan tic region. Tu dor Tãmaº and Bogdan P. Onac, Quater nary Re search Group, “Babeº-Bolyai” Uni ver sity, Kogãlniceanu 1 and “Emil Racoviþã” In - sti tute of Spe le ol ogy, Clinicilor 5, 400006 Cluj-Napoca, Ro ma nia, e-mails: [email protected], [email protected]; Ana-Voica Bojar, Insti tute of Earth Sci ences, Karl-Franzens Uni ver sity, Heinrichstrasse 26, A-8010 Graz, Austria, e-mail: [email protected] (receiv ed: Decem ber 28, 2004; accepte d: April 15, 2005). Key words: NW Ro ma nia, Lateglacial-Mid dle Ho lo cene, sta lag mites, sta ble iso topes, ura nium-tho rium TIMS dating. INTRODUCTION tope pro files on two sta lagm ites from northwest ern Ro mania. The d18O and d13C speleothem re cords show sim i lar i ties with the Green land ice core re cords (Dansgaard et al., 1989; Calcium carbon ate de pos its from caves, such as sta lag mites Johnsen et al., 1997) and are corre lat ed with pol len records, or flowstones, provide in form ati on on the na ture of past cli - lake sed i ments and veg e ta tion dy nam ics (Wohlfarth et al., mates and en vi ron ments. Changes of cli ma tic con di tions were 2001; Björkman et al., 2002; Bodnariuc et al., 2002; Feurdean shown to in flu ence sta ble iso tope geo chem is try dur ing and Bennike, 2004; Magny, 2004). speleothem de po si tion (Hendy and Wil son, 1968; McDermott, 2004). The timing of past cli matic shifts in such con ti nen tal re - cords is im por tant for com pari sons with marine or ice core re- SITE DESCRIPTION cords and for reconstructions of climate variability. U-Th TIMS dating of speleothems provides good preci sion of result s in terms of radio m etric ages and sam ple stra tigra phy The V11 Cave is locat ed in the south eastern part of (Li et al., 1989; Richards and Dorale, 2003). Speleothems Vãrãºoaia Glade (Bihor Mountai ns, NW Rom ania) , at 1254 m dated by TIMS pro vide valuable palaeoclimatic in for ma tion a.s.l. (Fig. 1A). The area is a typ ical karst pla teau with sink - when as soci ate d with other proxies such as d18O and d13C iso - holes and ponors and the vege ta ti on consis ts mainly of spruce to pic com po si tion of cal cite (Dorale et al., 1998; McDermott et stands and alpine herbs (Bodnariuc et al., 2002). The mean an - al., 1999; McDermott, 2004; Wil liams et al., 2005). nual tem per a ture is 5°C and the mean an nual precip i ta ti on ex- In this study we present a recon struc tion of Lateglacial- ceeds 1200 mm at the Stâna de Vale win ter resort (1102 m Mid-Ho lo cene cli mate changes based on con tin u ous sta ble iso- a.s.l), 11 km NW from the cave. The pres ent-day cli mate of the 186 Tudor Tãmaº, Bogdan P. Onac and Ana-Voica Bojar Fig. 1. A — geograph ical lo cation of the V11 Cave; karst areas are marked in black, the gray circle marks the Bihor Moun tains; B — plan and lon gi tudi nal sec tion of the V11 cave show ing the sampling site of sta lag mites S22 and S117 area is pre dom i nantly in flu enced by west-north west oce anic air Sam ple S117 (Fig. 2B) is 48 cm in height (measured along masses, with the South ern Carpathians act ing as a bar rier the growth axes) and is very dif ferent from S22 in terms of against Med i ter ra nean in flu ences. shape and stra tig ra phy. The re peated dis place ment of its The V11 cave formed in Anisian car bon ate rocks: black growth axis was proba bly produced by slid ing over the clayey lime stones (Guttenstein fa cies) and grey dolostones. The cave sub stra tum. On the ba sis of mac ro scopic ob ser va tions, the sam - has 1166 m of survey ed pas sages, a verti cal exten sion of 67 m ple could be di vided into 4 zones with 10 differ ent growth axes (–37 m; +30 m), and it devel oped as a dendrit ic maze on four (Tãmaº and Causse, 2001): main karstification lev els (Damm, 1993; Fig. 1B). The I. 0–9 cm: from the base to a frac ture line covered by subse - speleothems are re stricted to a few sec tors and con sist of cal cite quent de po siti on (growth axes A10–A8); thin growth levels , sta lag mites, sta lac tites, old (fos sil) flowstones and some ar- slightly porous dark brown calcit e; agon ite crystal ag gre gates and crusts. Pres ent-day cal cite de - II. 9–29.5 cm (A7–A5); light brown to white com pact cal - pos its oc cur as soda straws and small active sta lag mites. cite lamina, with a small growth hi a tus at 25 cm, marked by a The two sta lagm ites (S22 and S117), both inac ti ve when thin film of clay. This sequence ended when the stalag m ite sampled, were col lected 200 m away from the cave en trance, at broke (not shown in Fig. 2B); about 60 m below the surface (Fig. 1B). The first one grew on a III. 29.6–36.4 cm (A4–A2); de po siti on resum ed and youn - breakdown block and the sec ond on clay de posit ed on the pas- ger growth layers cov ered the frac ture sep a rat ing zones I and II; sage floor. Sev eral ac tive soda straws from their close vi cin ity yel low ish white, trans par ent, al ter nat ing com pact and po rous were sampled for re cent cal cite and drip wa ter iso to pic anal y- cal cite lev els; ses. The mean an nual temper a ture and the rel a tive hu mid ity of IV. 32.5–48 cm (A1). The sta lagm ite slipped once more the cave air, measured be tween 2003 and 2004, are 6.5°C and over the substra tum and the younger growth lay ers partly cov - 97–98%, re spec tively. ered zone III, in ducing a hi atus of ~0.6 ka. U-Th DATING SAMPLE DESCRIPTION AND ANALYTICAL PROCEDURES The U and Th rati os were measured in peak jump ing mode on a Finnigan-MAT 262 ther mal ion iza tion mass spec trom e ter SAMPLE DESCRIPTION at the Laboratoire des Sci ences du Climat et de l’Environ- nement, Gif sur Yvette, France. De tails of the re search and Sample S22 is a 34 cm-tall sta lag mite con sist ing mostly of chem i cal pro ce dure are given by Tãmaº and Causse (2001). A dense, yellow-brown, low-Mg calcit e laminae, com posed of total of 21 sam ples (12 from S22 and 9 from S117) from the up- large prism atic crystal s, conti n u ously grown from one level to perm ost parts of the two sta lagm ites (15 to 5.6 ka) were se - another and ori ented oblique to the outer surface (Fig.