Bulletin of Volcanology

, 77:18 | Cite as

Calibrating the pTRM and charcoal reflectance (Ro%) methods to determine the emplacement temperature of ignimbrites: Fogo A sequence, São Miguel, Azores, Portugal, as a case study

  • Alessandra PensaEmail author
  • Massimiliano Porreca
  • Sveva Corrado
  • Guido Giordano
  • Raymond Cas
Research Article


The emplacement temperatures of three ignimbrites belonging to the 4.6-ka Fogo A plinian eruption sequence in São Miguel Island (Azores, Portugal) were determined using partial thermal remanent magnetization (pTRM) of lithic clasts and reflectance (Ro%) of charcoal fragments embedded within the deposits and collected at the same localities close to each other. The Fogo A sequence is characterised by a complex stratigraphy consisting of a thick plinian deposit interbedded with two intraplinian ignimbrites (here named “pink” and “black” intraplinian ignimbrite, respectively) and capped by a final ignimbrite (here named “dark brown” ignimbrite). A total of 140 oriented lithic clasts from the three ignimbrites were collected from 15 localities distributed along the northern and southern flanks of the volcano. The pTRM analyses show different paleomagnetic behaviours, which correspond to different emplacement temperatures of the ignimbrites. The emplacement temperatures of the pink and black intraplinian ignimbrites inferred from pTRM analysis were respectively ≥400 and ≥600 °C; the temperatures of the dark brown ignimbrite are lower, estimated between 300 and 350 °C. Thermal estimations of three key sites were compared with the results of the analysis of reflectance (Ro%) measured on eight specimens derived from charcoal fragments collected from the pink intraplinian ignimbrite and the dark brown ignimbrite. Results indicate Ro% values between 1.61 and 1.37 for the pink intraplinian ignimbrite, whereas fragments collected from the dark brown ignimbrite show Ro% values between 0.85 and 0.50. No charred wood was found in the black intraplinian ignimbrite. Ro% values indicate that charcoal fragments in the pink intraplinian ignimbrite reached temperatures of 380–460 °C, whereas the Ro% values of the dark brown ignimbrite indicate slightly lower temperatures of 330–350 °C. TRM and Ro% results are comparable and validate the use of both methods. Greatest accuracy in the determination of emplacement temperatures of ignimbrites is achieved when both methods can be applied at the same locations.


Ignimbrite emplacement temperature Thermal remanent magnetization Charcoal reflectance Fogo A eruption sequence 



We would like to thank Roma Tre University for use of the paleomagnetic and reflectance facilities and CVARG Centre, University of Azores, São Miguel, for the kind hospitality during the field work. We particularly thank Prof. N. Wallenstein for useful indications about the stratigraphy of Fogo A and Prof. M. Mattei and Dr. F. Cifelli for their support for paleomagnetic measurements. We are also grateful to the reviewers of this manuscript (M. Ort, J. Hower and Anonymous Reviewer) as well as the editor (S. Fagents) for the detailed and constructive comments, which have resulted in a much improved paper. This research forms part of the PhD research of A. Pensa at Monash University, supported by discretionary research funds of Emeritus Professor R.A.F. Cas.


  1. Aramaki S, Akimoto S (1957) Temperature estimation of pyroclastic deposit by natural remanent magnetization. Am J Sci 255:619–627CrossRefGoogle Scholar
  2. Arroyo JM, Rigueiro C, Rodríguez R, Hampe A, Valido A, Rodríguez-Sánchez F, Jordano P (2010) Isolation and characterization of 20 microsatellite loci for laurel species (Laurus, Lauraceae). Am J Bot 97(5):26–30CrossRefGoogle Scholar
  3. Ascough PL, Bird MI, Scott AC, Collinson ME, Cohen-Ofri I, Snape CE, Le Manquais K (2010) Charcoal reflectance measurements: implications for structural characterization and assessment of diagenetic alteration. J Archaeol Sci 37:1590–1599CrossRefGoogle Scholar
  4. Ascough PL, Bird MI, Francis SM, Thornton B, Midwood AJ, Scott AC, Apperley D (2011) Variability in oxidative degradation of charcoal: influence of production conditions and environmental exposure. Geochim Cosmochim Acta 75:2361–2378CrossRefGoogle Scholar
  5. Bardot L (2000) Emplacement temperature determinations of proximal pyroclastic deposits on Santorini, Greece, and their implications. Bull Volcanol 61:450–467CrossRefGoogle Scholar
  6. Bardot L, McClelland E (2000) The reliability of emplacement temperature estimates using palaeomagnetic methods, a case study from Santorini, Greece. Geophys J Int 143(1):39–51CrossRefGoogle Scholar
  7. Bardot L, Thomas R, McClelland E (1996) Emplacement temperatures of pyroclastic deposits on Santorini deduced from palaeomagnetic measurements: constraints on eruption mechanisms. Geol Soc Lond, Spec Publ 105(1):345–357CrossRefGoogle Scholar
  8. Booth B, Croasdale R, Walker GPL (1978) A quantitative study of five thousand years of volcanism on São Miguel, Azores. Philos Trans R Soc A Math Phys Eng Sci 288(1352):271–319CrossRefGoogle Scholar
  9. Burden RE, Chen L, Phillips JC (2013) A statistical method for determining the volume of volcanic fall deposits. Bulletin of Volcanology 75(6):1–10Google Scholar
  10. Bursik MI, Sparks RSJ, Gilbert JS, Carey SN (1992) Sedimentation of tephra by volcanic plumes: 1. Theory and its comparison with a study of the Fogo A Plinian deposit, São Miguel (Azores). Bull Volcanol 54:329–344CrossRefGoogle Scholar
  11. Capaccioni B, Forjaz VH, Martini M (1994) Pyroclastic flow hazard at Agua de Pau Volcano (São Miguel Island, Azores Archipelago) inferred from the Fogo A eruptive unit. Acta Vulcanol 5:41–48Google Scholar
  12. Chadima M, Hrouda F (2006) Remasoft 3.0 a user-friendly paleomagnetic data browser and analyser. Travaux Geophysique XXVII:20-21Google Scholar
  13. Cioni R, Gurioli L, Zannella E (2004) Temperatures of the A.D. 79 pyroclastic density current deposits (Vesuvius, Italy). J Geophys Res 109(B02):1–18Google Scholar
  14. Correia M, Maury R, Arai F (1974) Mesure par leur Pouvoir Refecteur, des temperatures de carbonisation des bois fossilises dans les formations volcaniques. Bull du Centre de Recherches de Pau 8(2):527–536Google Scholar
  15. Di Chiara A, Speranza F, Porreca M (2012) Paleomagnetic secular variation at the Azores during the last 3 ka. J Geophys Res 117(B7):1–16CrossRefGoogle Scholar
  16. Di Vito MA, Zanella E, Gurioli L, Lanza R, Sulpizio R, Bishop J, Tema E, Boenzi G, Laforgia E (2009) The Afragola settlement near Vesuvius, Italy: the destruction and abandonment of a Bronze Age village revealed by archaeology, volcanology and rock-magnetism. Earth Planet Sci Lett 277(3–4):408–421CrossRefGoogle Scholar
  17. Downey WS, Tarling DH (1991) Reworking characteristics of Quaternary pyroclastics, Thera (Greece), determined using magnetic properties. J Volcanol Geotherm Res 46(1–2):143–155CrossRefGoogle Scholar
  18. Fisher RA (1953) Dispersion on a sphere. Proc R Soc Lond 217:295–305CrossRefGoogle Scholar
  19. Froggatt PC, Wilson CJN, Walker GPL (1981) Orientation of logs in the Taupo Ignimbrite as an indicator of flow direction and vent position. Geology 9:109–111CrossRefGoogle Scholar
  20. Hoblitt RP, Kellogg KS (1979) Emplacement temperatures of unsorted and unstratified deposits of volcanic rock debris as determined by paleomagnetic techniques. Geol Soc Am Bull 90(7):633–642CrossRefGoogle Scholar
  21. Hoblitt RP, Reynolds RL, Larson EE (1985) Suitability of non-welded pyroclastic-flow deposits for studies of magnetic secular variation: a test based on deposits emplaced at Mount St. Helens, Washington, in 1980. Geology 13:242–245CrossRefGoogle Scholar
  22. Hudspith VA, Scott AC, Wilson CJN, Collinson ME (2010) Charring of woods by volcanic processes: an example from the Taupo ignimbrite, New Zealand. Palaeogeogr Palaeoclimatol Palaeoecol 291(1–2):40–51CrossRefGoogle Scholar
  23. Jones TP, Scott AC, Cope MJ (1991) Reflectance measurements against temperature of formation for modern charcoals and their implications for the study of fusain. Bull Soc Géol Fr 162:193–200Google Scholar
  24. Kent DV, Ninkovitch D, Pescatore T, Sparks RSJ (1981) Palaeomagnetic determination of emplacement temperatures of Vesuvius AD 79 pyroclastic deposits. Nature 290:393–396CrossRefGoogle Scholar
  25. Lesti C, Porreca M, Giordano G, Mattei M, Cas RAF, Write HMN, Folkes CB, Viramonte JG (2011) High-temperature emplacement of the Cerro Galan and Toconquis Group ignimbrites (Puna plateau, NW Argentina) determined by TRM analyses. Bull Volcanol 73(10):1535–1565CrossRefGoogle Scholar
  26. Martí J, Diez-Gil JL, Ortiz R (1991) Conduction model for the thermal influence of lithic clasts in mixtures of hot gases and ejecta. J Geophys Res Solid Earth 96(B13):21879–21885CrossRefGoogle Scholar
  27. Mastrolorenzo G, Petrone PP, Pagano M, Incoronato A, Baxter PJ, Canzanella A, Fattore L (2001) Herculaneum victims of Vesuvius in AD 79. Nature 410:769–770CrossRefGoogle Scholar
  28. McClelland EA, Druitt TH (1989) Paleomagnetic estimates of emplacement temperatures of pyroclastic deposits on Santorini, Greece. Bull Volcanol 51(1):16–27CrossRefGoogle Scholar
  29. McClelland EA, Thomas R (1990) A palaeomagnetic study of Minoan age tephra from Thera. In: Hardy D (ed) Thera and the Aegean World III. The Theran Foundation, London, pp 129–138Google Scholar
  30. McClelland E, Wilson CJN, Bardot L (2004) Palaeotemperature determinations for the 1.8-ka Taupo ignimbrite, New Zealand, and implications for the emplacement history of a high-velocity pyroclastic flow. Bull Volcanol 66(6):492–513CrossRefGoogle Scholar
  31. Moore RB (1990) Volcanic geology and eruption frequency, Silo Miguel, Azores. Bull Volcanol 52:602–614CrossRefGoogle Scholar
  32. Ort MH, Rosi M, Anderson CD (1999) Correlation of deposits and vent locations of the proximal Campanian Ignimbrite deposits, Campi Flegrei, Italy, based on natural remanent magnetization and anisotropy of magnetic susceptibility characteristics. J Volcanol and Geotherm Res 91(2–4):167–178CrossRefGoogle Scholar
  33. Ort MH, de Silva SL, Ort MH, Jiménez NC, Jicha BR, Singer BS (2013) Correlation of ignimbrites using characteristic remanent magnetization and anisotropy of magnetic susceptibility, Central Andes, Bolivia. Geochem Geophys Geosyst 14(1):141–157CrossRefGoogle Scholar
  34. Paterson GA, Roberts AP, Mac Niocaill C, Muxworthy AR, Gurioli L, Viramonte JG, Navarro C, Weider S (2010) Paleomagnetic determination of emplacement temperatures of pyroclastic deposits: an under-utilized tool. Bull Volcanol 72(3):309–330CrossRefGoogle Scholar
  35. Porreca M, Giordano G, Mattei M, Musacchio P (2006) Evidence of two Holocene phreatomagmatic eruptions at Stromboli volcano (Aeolian Islands) from paleomagnetic data. Geophys Res Lett 33, L21316CrossRefGoogle Scholar
  36. Porreca M, Mattei M, MacNiocaill C, Giordano G, McClelland E, Funiciello R (2008) Paleomagnetic evidence for low-temperature emplacement of the phreatomagmatic Peperino Albano ignimbrite (Colli Albani volcano, Central Italy). Bull Volcanol 70(7):877–893CrossRefGoogle Scholar
  37. Rodríguez-Sánchez F, Guzmán B, Valido A, Vargas P, Arroyo J (2009) Late Neogene history of the laurel tree (Laurus L., Lauraceae) based on phylogeographical analyses of Mediterranean and Macaronesian populations. J Biogeography 36(7):1270–1281CrossRefGoogle Scholar
  38. Sawada Y, Sampei Y, Hyodo M, Yagami T, Fukue M (2000) Estimation of emplacement temperatures of pyroclastic flows using H/C ratios of carbonized wood. J Volcanol Geotherm Res 104(1):1–20CrossRefGoogle Scholar
  39. Scott AC (2010) Charcoal recognition, taphonomy and uses in palaeoenvironmental analysis. Palaeogeogr Palaeoclimatol Palaeoecol 291:11–39CrossRefGoogle Scholar
  40. Scott AC, Damblon F (2010) Charcoal: taphonomy and significance in geology, botany and archaeology. Palaeogeogr Palaeoclimatol Palaeoecol 291:1–10CrossRefGoogle Scholar
  41. Scott AC, Glasspool IJ (2005) Charcoal reflectance as a proxy for the emplacement temperature of pyroclastic flow deposits. Geology 33(7):589–592CrossRefGoogle Scholar
  42. Scott AC, Glasspool IJ (2007) Observations and experiments on the origin and formation of inertinite group macerals. Int J Coal Geol 70(1–3):53–66CrossRefGoogle Scholar
  43. Scott AC, Sparks RSJ, Bull ID, Knicker H, Evershed RP (2008) Temperature proxy data and their significance for the understanding of pyroclastic density currents. Geology 36(2):143–146CrossRefGoogle Scholar
  44. Tanaka H, Hoshizumi H, Iwasaki Y, Shibuya H (2004) Applications of paleomagnetism in the volcanic field, a case study of the Unzen Volcano, Japan. Earth Planets Space 56:635–647CrossRefGoogle Scholar
  45. Walker GPL, Croasdale R (1970) Two Plinian-type eruptions in the Azores. J Geol Soc 127:17–55CrossRefGoogle Scholar
  46. Wallenstein N (1999) Estudo da história recente e do comportamento eruptivo do vulcão do Fogo (S.Miguel, Açores). A valiação preliminar do hazard. PHD thesis (not published) Departamento de Geociências Universidades dos Açores, São Miguel Island (Portugal)Google Scholar
  47. Wright J (1978) Remanent magnetism of poorly sorted deposits from the Minoan eruption of Santorini. Bull Volcanol 41(2):131–135CrossRefGoogle Scholar
  48. Zanella E, Gurioli L, Zannella E, Gurioli L, Lanza R, Sulpizio R, Bontempi M (2008) Deposition temperature of the AD 472 Pollena pyroclastic density current deposits, Somma Vesuvius, Italy. Bull Volcanol 70(10):1237–1248CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Alessandra Pensa
    • 1
    Email author
  • Massimiliano Porreca
    • 2
    • 4
  • Sveva Corrado
    • 3
  • Guido Giordano
    • 3
  • Raymond Cas
    • 1
  1. 1.Monash UniversityClaytonAustralia
  2. 2.Department of Physics and GeologyUniversity of PerugiaPerugiaItaly
  3. 3.Roma Tre UniversityRomeItaly
  4. 4.Centro de Vulcanologia e Avaliação de Riscos Geológicos (CVARG), Departamento de GeociênciasUniversidade dos AçoresPonta DelgadaPortugal

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