Geologica Acta: an international earth science journal ISSN: 1695-6133 [email protected] Universitat de Barcelona España

PUIGURIGUER, M.; ALCALDE, G.; BASSOLS, E.; BURJACHS, F.; EXPÓSITO, I.; PLANAGUMÀ, LL.; SAÑA, M.; YLL, E. 14C dating of the last Croscat volcano eruption (Garrotxa Region, NE Iberian Peninsula) Geologica Acta: an international earth science journal, vol. 10, núm. 1, 2012, pp. 1-5 Universitat de Barcelona Barcelona, España

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How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 ARTICLE IN PRESS 9 8 7 6 5 4 3 2 1 .geologica-acta.com o c . a t c a - 5 a - c 1 i g , o 2 l 1 o 0 e 2 g w. h w c w r 9 a 0 t M 7 a 1 , 0 e 1 0 n 0 i º 0 l N 0 n . o , 5 0 0 e 1 1 l . / b l 4 a o 4 V l 3 i 1 , a . a v A 0 t 1 c A : I a O c D i g o l o e G KEYWORDS at that time. The ages that we report are the youngest obtained for volcanic activity in the Iberian Peninsula. Iberian the in activity volcanic for obtained youngest the are reconstruction report climate we and that analysis ages palynological The time. our between that with at ages accord gavein are samples and BP, The cal made. years were 15710 volcano and Croscat 13160 the of deposits fall pyroclastic volcanic under f h Grox (E bra Pnnua. Four Peninsula). Iberian (NE Garrotxa region volcanic the the in eruption of last the of study geochronological a of results the present we shortnote, this In M. PUIGURIGUERG.ALCALDEE.BASSOLSF. BURJACHSI.EXPÓSITOLL.PLANAGUMÀM.SAÑAE.YLL 2 Institut CatalàdeRecercaenPatrimoniCultural,UniversitatGirona,SpainE-mail:[email protected] Geochronology. Carbon-14. Croscatvolcano.Quaternary. Olot.Spain. 5 Institut CatalàdePaleoecologiaHumanaiEvolucióSocial(IPHES),Tarragona, Catalonia,Spain 1 14 3 4 Parc NaturaldelaZonaVolcànica delaGarrotxa,SpainE-mail:[email protected] C datingofthelastCroscatvolcanoeruption Institució Catalana de Recerca i Estudis Avançats (ICREA). Barcelona, Catalonia, Spain (Garrotxa Region,NEIberianPeninsula) 7 6 Universitat AutònomadeBarcelona,SpainE-mail:[email protected] Tosca. Equipd’educacióambiental,SpainE-mail:[email protected] 2 F. BurjachsE-mail:[email protected] 1 E-mail: [email protected] E-mail: [email protected] Axial. GeologiaiMediAmbientSL 3 14 S B A aayi o ognc atr otie i plesl located palaeosols in contained matter organic of analysis C T C A R T 4 5 6 7

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2 1 4 3 6 5 8 7 ARTICLE IN PRESS 9 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 ARTICLE IN PRESS 9 8 7 6 5 4 3 2 1 . l a t e R E U G I R U G I U P . M “LaPomareda”, resulted in 11.500 flow from the secondary cone the Croscatof volcano, called thermoluminescenceanalysis of basanite the on carried out geochronological information Croscat the volcano one of is volcanic region of the Garrotxa, because remains of this of remains because Garrotxa, the of the region in volcanic possible been not has itself eruption volcanic the OUTCROPS AND SAMPLING e.g., Smithsonian Global Volcanism Program).lyactive ornot (those with eruptions older than 10000 years; has implications for the classification of theand Europeanarea asrifts, volcanicalrobust knowledge of the youngest activity ingof the regional evolution of the volcanism in the Garrotxa isotopes for the first time. Aside fromto an the increased Croscat volcano understand and these allow dating withet radioactive al., 1986). Here we report the findings of palaeosols related NE Iberian Peninsula (Fig. 1) and is part of the magmatic activ INTRODUCTION farprecluded dating by the Ar-Aror lowKvolcanism, and the lack of carbonised remains have so canism in the Garrotxa area. The combination of a younghave age,been very few age determinations of the quaternary vol stratigraphic and geomorphologic observations (Fig.traditionally 2). Thereconsideredyoungestbeingthe judgingas from most recent of the peninsula, and the Croscatal.,1983). volcanicThevolcano activity hasaround probablyOlot beenis the Massif, the Rhine Valley and Eiffel in Germanyity of (e.g.,the European Araña riftet which goes through the French Central FIGURE 1 ) 9 2 0 1 7 0 1 2 0 ( 0 0 5 0 - 0 1 . 5 , 0 ) 1 1 / ( 4 0 4 1 3 1 , . a 0 t 1 c A : I a O c D i g o l o e G aig f abncos ln mte poue by produced matter plant carbonaceous of Dating The volcanic region of the Garrotxa (Olot) is located in the Geographical situation oftheCroscatvolcano. years+1.100 BP (Guérin 14 Ctechniques. Theonly - - - - period inwhichtheuseof a to attributable volcanoes of deposits fall pyroclastic the under or lavaflows under either found been not have type and the second (Torn-07) to a depth of 25 metres. In the In metres. 25 of depth a to (Torn-07) second the and metres 16.80 of depth del total a Pla to (Torn-06) first at the Torn: recovery core complete and drilling rotation using obtained were Croscat the of mantle pyroclastic the beneath palaeosol of Twosamples matter. organic in rich favoured the accumulation of sediments that are potentially little undergone change has and, at the same time, the shape record of a depression has sedimentary its result, a As volcano. Croscat the of eruption the before erosion major mantle emittedbythisvolcano. pyroclastic by filled and Torn, and Mallola Martinyà, de of the Croscat volcano formed by the volcanoes of the Puig eruption the to prior complex volcanic a to corresponding conditions. The Pla del Torn is a closed, concave depression necessary the fulfilled Croscat, the of cone volcanic the of the eruption. to anterior material the fossilizes layer volcanic the since carbon, modern by contaminated not is carbon located the that assures mantle) pyroclastic the below 15metres and depth where the pre-volcanic deposit is found (between 12 the hand, other the On occurred. not had palaeosol the of erosion that sediment guarantees maximum organic with point an a at sample obtain pyroclastic to and essential was palaeosol it the deposit, between time of period minimal a the find To obtain deposit. this would of quem we ante terminus deposit, fall pyroclastic the below directly surface palaeosol the dating by that is hypothesis 4). The and 3 (Fig. Croscat the of volcanicbelowcone the FIGURE 2 hsorpial, hs ra a nt ey rn to prone very not was area this Physiographically, The area of Pla del Torn, located a few metres to the NE just Wedeposited organicsediments date to proceeded Photograph oftheCroscat volcano. 14 C datingoftheCroscatvolcanoeruptions 14 C ispossible. 2 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 ARTICLE IN PRESS 9 8 7 6 5 4 3 2 1 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 ARTICLE IN PRESS 9 8 7 6 5 4 3 2 1 deposit (Fig. 5). The four samples were analysed with the with analysed were samples four The 5). (Fig. deposit volcanic the beneath located column palaeosol the the from obtained in depth different at samples sediment four METHODS several months. hs, eae osat uig the during constant became phase, h srtgah ad rpe vlms ugs that suggest volumes erupted and stratigraphy The blankets. The blankets. first phreatomagmatic first scoria averageof to range short a of was eruption the of duration violent Strombolian phases, producing phases, Strombolian violent y h peeig phreatomagmatic preceding the by ascent rate initially increased at the western side of the 14 poor a such subsequent of that quality were Torn-07 in obtained samples The metres. 12.30 at intercepted was zone edaphic the second theanalysed from obtained the in while metres, 15 of depth a at waslocated palaeosol material the sample, first neatd ih a with interacted magma the which after explosions, Strombolian to shifted agr phreatomagmatic larger ocn euto satd ih fissural with started eruption volcano they couldnotbeused(Table 1). the emission of a lava a of emission the phase, and finally decreased until the end the until decreased finally and phase, in scoria in a-ih mr primitive more gas-rich, . l a t e R E U G I R U G I U P . M ) 9 2 0 1 7 0 1 2 0 ( 0 0 5 0 - 0 1 . 5 , 0 ) 1 1 / ( 4 0 4 1 3 1 , . a 0 t 1 c A : I a O c D i g o l o e G FIGURE 3 pyroclastic mantle of theCroscatvolcano. C AMS method in the Beta Analytic Radiocarbon Dating aicro dtn ws ple o a eune of sequence a on applied was dating Radiocarbon codn t D Tala t l (09 te Croscat the (2009) al. et Traglia Di to According

cone eruptions (Cimarelli et al., 2010), i.e., during i.e., 2010), al., et (Cimarelli eruptions cone

cone products of the Croscat complex revealthat complex Croscat the of products cone Field photograph of the level of silts and clays beneath the beneath clays and silts of level the of photograph Field

activity subsequently shifted into a second, a into shifted subsequently activity

hlo aufr ytm pooig the promoting system, aquifer shallow

cone. Bubble number density values

hs. h arvl f relatively a of arrival The phase. flow and consequent breaching of breaching consequent and flow 14

hs. h euto edd with ended eruption The phase.

am, osby decompressed possibly magma, C analysis was not possible and possible not was analysis C

the end of the Strombolian

ciiy doe three drove activity, iln Strombolian violent

aain activity, Hawaiian widespread tephra widespread

of the eruption. the of

the age fortheCroscateruption. the of beginning the at thirteenth millennium cal BP. least This dating confirms a recent at or BP, cal millennium fourteenth the of end the at possibly place, took eruption the Thus, probability). (95% BP cal between years 13.270-13.040 deposited probably very was (14.90m) Torn-06sample the of level silt-clay the sedimentation of part a upper The indicates rate. sequence dated the so other, the from thehighestsample(Fig.7). apart to 20cm due is sample be this also that given could rate, sedimentation it but sample, the to applied differentpre-treatment the of result the be could This rest. the from distant more slightly is 15.10 to corresponds that the strata, and they are very similar in age. Only the dating calibration data go from oldest the to most recent as they and move up through age radiocarbon the both consistent: BP internally cal are results years age The 6). 13.270-13.040 (Fig. probability) (95% and BP cal years 13.160 BP,cal 13.410- BP,years cal 14.110-13.780 years 15.410 samples were, from bottom to top in the sequence: 16.030- RESULTS alkali/acid pre-treatment. with an acid wash, whereas the lower one pre-treated received an acid/ were ones higher three The pre-treatment. in difference a required matter in difference The one. lower the for used was residues palynological a of whereas concentration ones, organic higher three varied: the dated for used be was sediment to material The 2004). al., (Reimer et dating calibrated Florida), (Miami, Laboratory FIGURE 4 the levelofdatedsilts andclays.oftheCroscatvolcano. The four samples are significantly different from each from different significantly are samples four The four the of dating calibrated from obtained results The Field photograph of the pyroclastic level. Located on top of top on Located level. pyroclastic the of photograph Field

14 C datingoftheCroscatvolcanoeruptions 3

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2 1 4 3 6 5 8 7 ARTICLE IN PRESS 9 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 ARTICLE IN PRESS 9 8 7 6 5 4 3 2 1 . l a t e R E U G I R U G I U P . M TABLE 1 nlsd o wih ny or rvdd piu results optimum provided four only were which 16.50m) of and analysed, 14.90 (between samples 12 total, In used. were sediments lacustrine from potentially were that samples only analysis, palynological For Torn-06sample. time of the eruption, corresponding to the upper part of the RECONSTRUCTION PALYNOLOGICAL ANALYSIS AND CLIMATE FIGURE 5 (volcà delCroscat). ) 9 2 0 1 7 0 1 2 0 ( 0 0 5 0 - 0 1 . 5 , 0 ) 1 1 / ( 4 0 4 1 3 1 , . a 0 t 1 c A : I a O c D i g o l o e G Laboratory / number / Laboratory 2 sygma calibrated result (95% probability) calibrated (95% resultsygma 2 Intercept radiocarbon age / calibration curve calibrationcurve ageradiocarbon/ Intercept Sample Torn-06 (depth in meters) (depth in meters) Torn-06 Sample Conventional radiocarbon ageradiocarbon Conventional Pollen analysis of several samples was carried out to the Results oftheagedeterminationusing ytei clm o te aeil sd n h 1 the in used material the of column Synthetic 14 C dating(inyears) 16 030 -15 410 cal BP BP cal 410 -15 030 16 13 260 + 50 BP BP 50 + 260 13 Beta-225 760 760 Beta-225 15 710 cal BP BP cal 710 15 st survey 15,10 15,10 14 110 -13 780 cal BP BP cal 780 -13 110 14

mesophiles, of presence the hand, other the On passed. had Maximum symptom of the beginning of thawing once the Last Glacial warmestthe of areas sheltered the in type) a microclimate, yr-yrpye (Cyperaceae, of presence hygro-hydrophytes the by demonstrated also is which rainfall, and Alnus (Ulmus, trees the resultsthatwehave obtainedbyabsolute ‘GI-1b’ the in temperature event. in drop the indicate would in increase Subsequently,the Tardiglacial.from Bölling-Alleröd of complex interstadial ‘GI-1c’ event of Walker et al. (1999), focused on the classic Sparganium, wherewecouldalsoinclude Apiaceae). of trees could be found (Quercus spp., with coveredgrasses (Poaceae), Asteraceae and meadows/steppes of made was plant landscape This 28.5%. and 72.2 between values AP with 7), al. et Burjachs in (2003). out set protocol the to according and Renault-Miskovsky,and (Girard acetolysis 1969), without (1979), technique Beaulieu and Goeury the to treated according were samples The 15.20m). and 15.00 (between ACKNOWLEDGMENTS FIGURE 6 carried outinPladel Torn. 14.90 15.00 15.05 15.10 T-06 12.500 According to isotope dating, this period belongs to the to belongs period this dating, isotope to According (Fig. landscape open an reveals spectrum pollen The 12 090 + 60 BP BP 60 + 090 12 Beta-244 068 068 Beta-244 13 950 cal BP BP cal 950 13 These results confirm this chronological period and period chronological this confirm results These rpi rpeetto o te eain among relation the of representation Graphic 15,05 15,05 Quercus, 13.500 13 410 -13 160 cal BP BP cal 160 -13 410 13 Acer and 14 C datingoftheCroscatvolcanoeruptions 11 420 + 60 BP BP 60 + 420 11 Beta-245 869 869 Beta-245 13 270 cal BP BP cal 270 13 idct a ices in increase an indicate Salix) 14.500 in the 15.00m sample 15.00m the in Pinus Corylus, as well as riverside 15,00 15,00

Artemisia, where groups and Alisma Acer spp, 13 270 -13 040 cal BP BP cal 040 -13 270 13 15.500 11 260 + 60 BP BP 60 + 260 11 14 Beta-245 868 868 Beta-245 13 160 cal BP BP cal 160 13 C dating. Castanea- 14 cal cal BP datings C Typha- 14,90 14,90 16.500 4 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 ARTICLE IN PRESS 9 8 7 6 5 4 3 2 1 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 ARTICLE IN PRESS 9 8 7 6 5 4 3 2 1 contents ofthistext. Scaillet and M. Ort, who we would like to thank for orienting the S. Mr Costa, F. Mr of annotations and contributions interesting Cimarelli, C., Di Traglia,F.,C., Cimarelli, Taddeucci,scoria Basaltic 2010,. J., Metodología 2003. M.J., Iriarte, J.A., F.,López-Sáez, Burjachs, L., García-Cacho, C., Martín-Escorza, A., V.,Aparicio, Araña, REFERENCES . l a t e R E U G I R U G I U P . M ) 9 2 0 1 7 0 1 2 0 ( 0 0 5 0 - 0 1 . 5 , 0 ) 1 1 / ( 4 0 4 1 3 1 , . a 0 t 1 c A : I a O c D i g o l o e G FIGURE 7 on AP. o te elzto o ti nt w cud on o the on count could we note this of realization the For 2010, 38,439-442. bolian activity. Geological Society of America, Geology, May textures from a zoned conduit as precursors to violent Strom- 11-18. Catalunya, de d’Arqueologia Museu Barcelona, todológicas. da de muestras en arqueobotánica: objetivos y propuestas me- arqueopalinológica. In: Buxó, R., Piqué, R. (eds.). La recogi- cos. Acta GeologicaHispanica,18,1-17. geodinámi- y petrológicos estructurales, caracteres alunya: Cat- de neógeno-cuaternario volcanismo El 1983. X., siot, R., Ortiz, Vaquer,F.,Barberi, R., G., Gas- Ferrara, J., Albert, Pollen diagram of selected taxa from the Pla del Torn deposit. The black dots indicate a presence of less than 1%. Pinus curve is overlay is curve Pinus 1%. than less of presence a indicate dots black The Torndeposit. del Pla the from taxa selected of diagram Pollen Reimer, P.J. et al., 2004. INTCAL04 Terrestrial radiocarbon age cali exemple Un 1986. J.M., Mallarach, G., Bemhamou, G, Ghérin, Goeury, Cl., Beaulieu, J.L. de, 1979. À propos de la concentration techniques Nouvelles 1969. J., Renault‑Miskovsky, M., Girard, Walker, M.J.C., Björck, S., Lowe, J.J., Cwynar, L.C., Johnsen, S., D., Torrente,Gimeno D., Rita, De C., Cimarelli, F.,Traglia, Di published OnlineSeptember2011. revision acceptedDecember2010; Manuscript receivedJanuary2010; de Catalunya. Vitrina, 1,19-26. de fusió parcial en medi continental. El vulcanisme quaternari minéraux, PollenetSpores,XXI(1-2),239-251. du pollen à l’aide de la liqueur de Thoulet dans les sédiments Quaternaire, 4,275-284. du l’Étude pour Française l’Association de Bulletin Rhône). (Istres Cornille l’Abri de final Quaternaire sediments du trois à appliqués Palynologie en préparation de Pleistocene. QuaternaryScienceReviews, 18,1143-1150. Late the for stratotype a core: ice GRIP ‘events’the topic in Wohlfarth,K.L., INTIMATEIso- Knudsen, B., 1999. group, ogy andGeothermalResearch,180,89-109. Volcanolof Journal - Peninsula). Iberian (NE VolcanicField Garrotxa cone, scoria complex Croscat from examples ism: volcanexplosive- basaltic in styles eruptive Changing 2009. bration, 0-26 Cal KYR BP. Radiocarbon, 46-3, 1029-1058. 14 C datingoftheCroscatvolcanoeruptions Bouches du Bouches ‑

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