Notas finales tercer periodo
OBJETIVOS DE APRENDIZAJE
Table 3.8 An example of D2 statistics from canconical DFA: Rk samples from Lake
Rotokare are compared to selected M05 samples of edifice location 2 (see Figure 2.1 and Appendix 4).
M05-61 M05-67 M05-69 M05-70 M05-74 M05-75 M05-78 Rk-25 0.419 3.502 15.019 11.512 16.588 10.886 14.183 Rk-26 0.085 2.476 13.173 9.615 14.876 9.024 12.301 Rk-27 0.687 1.286 8.673 5.250 9.015 4.561 7.411 Rk-29 1.348 1.222 6.687 3.731 6.813 3.411 5.649 Rk-30 2.413 0.228 6.278 5.994 9.930 5.768 6.382 Rk-31 5.830 0.925 1.896 3.042 5.210 3.438 2.421 Rk-32 13.354 8.822 7.013 8.807 11.065 10.987 8.809 Rk-33 13.332 5.573 0.585 2.182 1.559 2.660 0.653 Rk-34 5.600 2.557 4.565 3.143 3.485 2.234 3.178 Rk-35 8.532 2.698 0.929 2.151 3.332 2.871 1.420 Rk-36 7.679 2.493 1.051 0.469 1.387 0.513 0.428 Rk-37 7.098 2.421 1.590 0.520 1.391 0.344 0.680 Rk-39 10.798 3.472 1.493 2.542 4.110 2.602 1.487 Rk-40 9.047 2.661 0.317 1.121 2.126 1.532 0.388 Rk-41 15.212 7.533 1.165 1.580 0.547 2.039 0.659 Rk-43 5.991 1.321 1.714 1.364 2.658 1.133 1.150 Rk-44 6.287 1.087 1.559 2.584 4.236 2.766 1.811 Rk-46 10.449 3.147 0.218 1.682 2.489 2.041 0.431 Rk-47 6.933 1.806 3.882 4.673 5.670 3.794 3.374 Rk-48 6.741 1.629 1.402 1.909 2.909 1.956 1.266 Rk-49 20.936 14.149 6.209 4.823 1.807 4.870 4.483 Rk-50 16.008 9.714 4.068 2.151 0.264 1.693 2.068
The titanomagnetite dataset from the well dated lacustrine deposits (see 3.2 – 3.12 and Chapter 2 for further details) are used as the reference dataset for canonical DFA analyses of those titanomagnetites from the edifice deposits. The D2 values of the canonical DFA are listed in Appendix 4 and an example is given in Table 3.6. The D2 statistic of these datasets is highly dependent on the spread of compositional data from each tephra within the reference dataset. With larger compositional spreads, there is a higher likelihood that unknown tephras will fit into several groups and the resulting D2 will be relatively small. To overcome this problem, and identify likely matched tephras from one or more deposits, all D2 statistics from each deposit were grouped and a 95 percentile found. Any compositions that had a D2 statistic within this percentile were classified as having similar titanomagnetite compositions (Appendix 4). Using these datasets and also forcing stratigraphic order within the each of the profiles, correlation of the lacustrine records to the sampled edifice tephras was achieved (Appendix 4). Individual eruptions can be distinguished on the basis of this technique. Temporal groupings of possible correlatives are also observed, and are discussed further in Chapter 4 (4.7-4.15). Each of these temporal groupings of similar titanomagnetite compositions appears to represent the eruption of a chemically distinct magma “batch”. Within the lake records, eight magma batches were identified. Figure 3.11 groups the correlations made by canonical DFA into these defined magma batches. This shows the 12 main stratigraphic profiles defined in Chapter 2 and is hinged upon the first identifiable scoria-bearing basaltic-andesite eruption, termed the Manganui-A (Alloway et al. 1995), which on correlation to the Rotokare core occurred c. 3100 yrs B.P.
Figure 3.12: Correlation diagram of edifice stratigraphic sites identified in Chapter 2.
Each site is correlated to the better-dated eruption records of Lakes Umutekai and Rotokare by canonical DFA on titanomagnetite compositions. The correlations are simplified and grouped into the temporally defined eruption of the magma batches as identified in Chapter 4.
3.12 Conclusions
The compositions of titanomagnetite microphenocrysts are unique to most individual magmas and magma batches erupted from Mt. Taranaki. Hence the correlation of eruptions from this volcano can be made on the basis of these compositions, using multi-parameter statistical techniques such as Principal Component Analysis (3.2-3.13) or Canonical Discriminant Function Analysis. The compositions of the titanomagnetite phenocrysts are not always unique to a single eruption, but always relate to a compositionally and temporally defined magma batch. Therefore the methods identified here need to be used in conjunction with detailed field descriptions, physical characteristics of the deposit, and/or geochemistry of other mineral phases in order to correlate all units.
3.13 References
Alloway B, Lowe DJ, Chan RPK, Eden D, Froggatt P (1994) Stratigraphy and Chronology of the Stent Tephra, a C-4000 Year-Old Distal Silicic Tephra from Taupo-Volcanic-Center, New-Zealand. NZ J Geol Geophys 37: 37-41.
Alloway B, Neall VE, Vucetich CG (1995) Late Quaternary (post 28,000 year BP) tephrostratigraphy of northeast and central Taranaki, New Zealand. J R Soc NZ 25: 385- 458.
Bebbington MS (2007) Identifying volcanic regimes using hidden Markov models. Geophys J Int 171: 921-942.
Bebbington MS, Lai CD (1996a) On nonhomogeneous models for volcanic eruptions. Math Geol 28: 585-600. DOI 10.1007/BF02066102.
Bebbington MS, Lai CD (1996b) Statistical analysis of New Zealand volcanic occurrence data. J Volcanol Geotherm Res 74: 101-110. DOI 10.1016/S0377-0273(96)00050-9.
Bebbington M, Cronin SJ, Chapman I, Turner MB (2008) Quantifying volcanic ash fall hazard to electricity infrastructure. J Volcanol Geotherm Res, 177: 1055-1062 doi:10.1016/j.jvolgeores.2008.07.023.
Best MG (2003) Igneous and metamorphic petrology. Blackwell Science. Malden.
Bronk-Ramsay C (2003) Oxcal Program v. 3.10: Oxford Radiocarbon Accelerator Unit, Oxford. Buddington AF, Lindsley DH (1964) Iron-titanium oxide minerals and synthetic equivalents. J
Petrol 5: 310-357.
Burt ML, Wadge G, Scott WA (1994) Simple stochastic modelling of the eruption history of a basaltic volcano: Nyamuragira, Zaire. Bull Volcanol 56: 87-97.
Carey S, Sparks RJS (1986) Quantitative models of the fallout and dispersal of tephra from volcanic eruption columns. Bull Volcanol 48: 109-125.
Cole JW (1990) Structural control and origin of volcanism in the Taupo Volcanic zone. Bull Volcanol 52: 445-459.
Connor CB, Hill BE (1995) Three nonhomogeneous Poisson models for the probability of basaltic volcanism: application to the Yucca Mountain region, Nevada. J Geophys Res 100: 10107-10125.
Cronin SJ, Neall VE, Stewart RB, Palmer AS (1996a) A multiple-parameter approach to andesitic tephra correlation, Ruapehu volcano, New Zealand. J Volcanol Geotherm Res 72: 199-215.
Cronin SJ, Wallace RC Neall VE (1996b) Sourcing and identifying andesitic tephras using major oxide titanomagnetite and hornblende chemistry, Egmont volcano and Tongariro Volcanic Centre, New Zealand. Bull Volcanol 58: 33-40.
Cronin SJ, Neall VE, Palmer AS, Stewart RB (1997) Methods of identifying late Quaternary rhyolitic tephra on the ring plains of Ruapehu and Tongariro volcanoes, New Zealand. NZ J Geol Geophys 40: 175-184.
Cronin SJ, Bebbington MS, Lai CD (2001) A probabilistic assessment of eruption recurrence on Taveuni volcano, Fiji. Bull Volcanol 63:274-288. DOI 10.1007/s004450100144.
De la Cruz-Reyna S, Carrasco-Nunez G (2002) Probabilistic hazard analysis of Citlaltepetl (Pico de Orizaba) volcano, eastern Mexican volcanic belt. J Volcanol Geotherm Res 113: 307-318.
Devine JD, Rutherford MJ, Norton GE, Young SR (2003) Magma storage region processes inferred from geochemistry of Fe-Ti oxides in andesitic magma, Soufriere Hills Volcano, Montserrat, WI. J Petrol 44: 1375-1400 (DOI:10.1093/petrology/44.8.1375).
Donoghue SL, Vallance J, Smith IEM, Stewart RB (2007) Using geochemistry as a tool for correlating proximal andesitic tephra:case studies from Mt. Rainier (USA) and Mt. Ruapehu (New Zealand). J Quat Sci 22: 395-410. DOI: 10.1002/jps.1065.
Druce AP (1966) Tree-ring dating of recent volcanic ash and lapilli, Mt. Egmont. NZ J Bot 4: 3- 41.
Eliasson J, Larsen G, Gudmundsson MT, Sigmundsson F (2006) Probabilistic model for erutpions and associated flood events in the Katla caldera, Iceland. Comp Geosci 10: 179- 200.
Fergusson GJ, Rafter TA (1957) New Zealand C14 measurements – 3. NZ J Sci Technol B38: 732–749.
Fleming CA (1976). The Quaternary record of New Zealand and Australia. In: Suggate, R.P., Cresswell, M.M. (Eds.), Quaternary Studies. R Soc NZ, Wellington, pp. 1–20.
Freer R, Hauptman Z (1978) Experimental study of magnetite-titanomagnetite interdiffusion. Phys Earth Planet Int 16: 223-231.
Froggatt PC, (1983) Toward a comprehensive Upper Quaternary tephra and ignimbrite stratigraphy in New Zealand using electron microprobe analysis of glass shards. Quat Res 19: 188-200.
Grant-Taylor TL, Rafter TA (1971) New Zealand radiocarbon measurements – 6. NZ J Geol Geophys 14: 364-402.
Grönvold K, Oskarsson N, Johnsen SJ, Clausen HB, Hammer CU, Bond G, Bard E (1995). Ash layers from Iceland in the Greenland GRIP ice core correlated with oceanic and land sediments. Earth Planet 135: 149–155.
Hunt JB, Hill PG (1993) Tephra geochemistry: a discussion of some persistent analytical problems. Holocene 3: 271-278. DOI: 10.1177/095968369300300310.
Jiang R, Murthy DNP (1995) Modelling failure data by mixture of two Weibull distributions: a graphical approach. IEEE Trans Reliab 44:477-488.
Jiang R, Murthy DNP (1998) Mixture of Weibull distributions- parametric characterization of failure rate function. Appl Stoch Mod Data Analysis 14:47-65.
Kohn BP (1970) Identification of New Zealand tephra-layers by emission spectrographic analysis of their titanomagnetites. Lithos 3: 361-368.
Johnson RA, Wichern DW (1992) Applied Multivariate Statistical Analysis (3rd Ed), Prentice
Hall Inc, New Jersey.
Lees CM, Neall VE (1993) Vegetation response to volcanic eruptions on Egmont Volcano, New Zealand, during the last 1500 years. J R Soc NZ 23: 91-127.
McGlone MS, Neall VE, Clarkson BD (1988) The effects of recent volcanic events and climate changes on vegetation of Mt. Egmont (Mt. Taranaki), New Zealand. NZ J Bot 26: 123- 144.
McGlone MS, Neall VE (1994). The late Pleistocene and Holocene vegetation history of Taranaki, North Island, New Zealand. NZ J Bot 32: 251-269.
Marzocchi W, Sandri L, Gasparini P, Newhall C, Boschi E (2004) Quantifying probabilities of volcanic events: The example of volcanic hazard at Mount Vesuvius. J Geophys Res 109: B11201.
Neall VE (1979) Sheets P19, P20, and P21. New Plymouth, Egmont and Manaia. 1st ed. Geological map of New Zealand 1:50,000. 3 maps and notes. New Zealand Department of Scientific and Industrial Research. Wellington.
Neall VE, Stewart RB, Smith IEM (1986) History and Petrology of the Taranaki Volcanoes. R Soc NZ Bull 23: 251-263.
Neall VE (1999) Stony River at the Blue Rata Reserve. Report to the Taranaki Regional Council, Taranaki, pp 13.
Perkins WT, Fuge R, Pearse NJG, Wintle AG (1994) Trace-element analysis of volcanic glass shards by laser ablation inductively coupled plasma mass spectrometry: application to tephronological studies. Anal Geochem 9: 323-335.
Platz T, Cronin SJ, Stewart RB, Smith IEM, Foley SF (2006) Magma changes during ascent and its impact on eruptive style: a study from Mt. Taranaki andesites, New Zealand. Geophys Res Abstracts 8: 00514.
Platz T, Cronin SJ, Smith IEM, Turner MB, Stewart RB (2007) Improving the reliability of microprobe-based analyses of andesitic glasses for tephra correlation. Holocene 17: 573- 585 DOI: 10.1177/0959683607078982.
SAS Institute Inc. (2004) SAS® Enterprise Guide® 3.0 Administrator: Users Guide. Cary NC:
SAS Institute Inc. 160 pp.
Shane P (2005) Towards a comprehensive distal andesitic framework for New Zealand based on eruptions from Egmont volcano. J Quat Sci 20: 45-57.
Simkin T, Siebert L (1994) Volcanoes of the World (2nd edition) Tucson: Geoscience Press, 369 pp.
Smith DR, Leeman WP (1982) Mineralogy and phase chemistry of Mount St Helens tephra set W and Y as keys to their identification. Quat Res 17: 211-227.
Smith VC, Shane P, Nairn IA (2005) Trends in rhyolite geochemistry, mineralogy, and magma storage during the last 50 kyr at Okataina and Taupo volcanic centres, Taupo Volcanic Zone, New Zealand. J Volcanol Geotherm Res 148: 372-406.
Srivastiva MS, Carter EM (1983) An introduction to Applied Multivariate Statistics. Elsevier Science Publishing Co Ltd, New York.
Stokes S, Lowe DJ (1988) Discriminant function analysis of late Quaternary tephras from five volcanoes in New Zealand using glass shard major element chemistry. Quat Res 30: 270- 283.
Stokes S, Lowe DJ (1988) Discriminant function analysis of late Quaternary tephras from five volcanoes in New Zealand using glass shard major element chemistry. Quat Res 30: 270- 283.
Stokes S, Lowe DJ, Froggatt PC (1992) Discriminant function anaysis and correlation of late Quaternary rhyolitic tephra deposits from Taupo and Okataina volcanoes, New Zealand, using glass shard major element composition. Quat Int 13/14: 103-117.
Stuiver M, Pearson GW (1992) Calibration of the 14C time scale 2500-5000 BC. In: Taylor RE, Long A, Kra RJ (eds) Radiocarbon dating after 4 decades: an interdisciplinary perspective, Springer, New York, pp 19-33.
Tomiya A, Takahashi E (2005) Evolution of the magma chamber beneath Usu Volcano since 1663: A natural laboratory for observing changing phenocryst compositions and textures. J Petrol 46: 2395-2426.
Turner MB, Cronin SJ, Bebbington MS, Platz T (2008a) Developing a probabilistic eruption forecast for dormant volcanos; a case study from Mt. Taranaki, New Zealand. Bull Volcanol 70: 507-515. DOI: 10.1007/s00445-007-0151-4.
Turner MB, Cronin SJ, Smith IEM, Bebbington MS, Stewart RB (2008b) Using titanomagnetite textures to elucidate volcanic eruption histories. Geology 36: 31-34. DOI: 10.1130/G24186A.1.
Ward, G. K.; Wilson, S. R. (1978) Procedures for comparing and combining radiocarbon age determinations: a critique. Archaeometry 20: 19-31.
Westgate JA, Gorton MP (1981) Correlation techniques in tephra studies. In Tephra Studies, Self S, Sparks RSJ (eds). D Reidel:Dordrecht, pp. 73-94.
Chapter Four:
Eruption Classification and Identification of Cyclic Volcanic
Processes at Mt. Taranaki.
This chapter consists of two parts. Firstly, a technique to distinguish two-end member eruption states using titanomagnetite textures is examined. The technique was applied to the deposits from Lake Umutekai and resulted in the identification of a periodic eruption rate from the volcano. The second part of the chapter examines the possible magmatic-system processes that are likely responsible for causing eruption periodicity.
4.1 Introduction
In the previous chapter, methods of andesitic tephrostratigraphy were developed to enable the combination of two or more records from differing sectors of the volcano and thus generate more accurate estimates of eruption frequency. Developing a full eruption record from andesitic volcanoes may, however, be an impossible task, since they produce a wide array of eruption products with highly varying deposition areas that often never overlap (e.g., lava-flows vs. tephra falls). To overcome this obstacle, it is more statistically valid to identify one particular eruption style, develop the best possible record for it, and then use this sub-sample of the eruption frequency as a proxy for the overall eruption frequency.
The first part of this chapter consists of the manuscript ‘Using titanomagnetite textures to elucidate volcanic eruption histories’ by: Michael B. Turner, Shane J. Cronin, Robert B. Stewart, Mark S. Bebbington and Ian E.M. Smith, published within Geology, (January 2008; vol. 36: 31-34). This manuscript outlines a method of using titanomagnetite textures to identify tephra-producing eruption styles in the context of two simplified end-members states: 1) fast magma-ascent eruptions, typically producing sub-plinian events and 2) slow-ascent eruptions, typically resulting in effusion of lava-
domes, deposition of associated block-and-ash-flows and co-pyroclastic flow ash falls. By using this method, it is shown that the frequency of sub-plinian eruptions at Mt. Taranaki is highly periodic, with a cyclic variation in eruption frequency that is of around 1500 years in amplitude.
The contributions of each author to the study were as follows:
Michael .B. Turner: Principal investigator:
Carried out: Field description and sampling
Laboratory preparation
Optical microscopy
Technique development
Electron microprobe analyses
Manuscript preparation and writing
Shane J. Cronin: Chief advisor:
Aided the study by: Assistance in the field
Discussion of methodology and results
Editing and discussion of the manuscript
Ian E.M. Smith, Robert B. Stewart: Advisors:
Aided the study by: Discussion of methodology and results
Editing and discussion of the manuscript
Mark S. Bebbington: Statistical advisor:
Aided the study by: Produced Fig. 4.5; the smoothed annual
eruption rate curve from Taranaki.
Editing and discussion of the manuscript
The second part of this chapter aims to identify the underlying causes of this periodic eruption frequency at Mt. Taranaki. By using titanomagnetite compositions as a proxy for the geochemistry of the magma just prior to eruption, it is demonstrated that the eruption frequency is parallel and in phase with an overall cyclic pattern of magma
evolution. This implies a genetic link between the two and has significant implications for developing possible time-variable hazard forecasting models from similar reawakening volcanoes.
The manuscript: ‘Cyclic magma evolution and associated eruption frequency at andesitic volcanoes and its implications to eruption forecasting: a case study from Mt. Taranaki, New Zealand’ by: Michael B. Turner, Shane J. Cronin, Robert B. Stewart, Mark S. Bebbington and Ian E.M. Smith will be submitted to Earth and Planetary Science Letters. The contributions of each author to the study were as follows:
Michael .B. Turner: Principal investigator:
Carried out: Field description and sampling
Laboratory preparation
EMP and XRF analyses
Manuscript preparation and writing
Shane J. Cronin: Chief advisor:
Aided the study by: Assistance in the field
Discussion of data, results and models
Editing and discussion of the manuscript
Ian E.M. Smith, Robert B. Stewart: Advisors:
Aided the study by: Discussion of data, results and models Editing and discussion of the manuscript
Mark S. Bebbington: Statistical Advisor:
Aided the study by: Produced Fig. 4.7; the smoothed, annual
eruption rate from Mt. Taranaki.
Discussion of data, results and models