Tephrochronology: Methodology and correlations, Antarctic Peninsula Area

Mats Molén Thesis in Physical Geography 30 ECTS Master’s Level Report passed: November 9 2012 Supervisor: Rolf Zale Tephrochronology: Methodology and correlations, Antarctic Peninsula Area

Abstract

Methods for tephrochronology are evaluated, in the following way: Lake sediments <500 years old from three small Antarctic lakes were analysed for identification of tephras. Subsamples were analysed for a) grain size, and identification and concentration of volcanogenic grains, b) identification of tephra horizons, c) element abundance by EPMA WDS/EDS and LA-ICP-MS, and d) possible correlations between lakes and volcanoes.

Volcanogenic minerals and shards were found all through the sediment cores in all three lakes, in different abundances. A high background population of volcanogenic mineral grains, in all samples, made the identification of tephra horizons difficult, and shards could only be distinguished by certainty after chemical analysis of elements. The tephra layers commonly could not be seen by the naked eye, and, hence they are regarded as cryptotephras. Because of the small size of recent eruptions in the research area, and the travel distance of ash, most shards are small and difficult to analyse.

Nine possible tephra horizons have been recorded in the three lakes, and preliminary correlations have been made. But because of analytical problems, the proposed correlations between the lakes and possible volcanic sources are preliminary. Table of contents

1. Introduction ...... 1 1.1. Advances and problems of tephrochronology ...... 1 1.1.1. General observations ...... 1 1.1.2. Difficulties in tephrochronology work ...... 2 1.1.3. The current research ...... 4 1.2. Identification of shards and chemical analyses of ashes ...... 4 1.2.1. Optical polarizing microscope ...... 4 1.2.2. Analyses of major, minor and trace elements ...... 5 1.2.2.1. General description of instruments used in tephrochronology ...... 5 1.2.2.2. Instrument limitations ...... 6 1.2.2.3. Necessary data for chemical analyses ...... 6 1.2.3. What elements are analysed? ...... 7 1.2.3.1. Major elements ...... 7 1.2.3.2. Minor/trace elements ...... 7 2. Area description and earlier work ...... 8 2.1. Geography of lakes and environment in the research area ...... 8 2.2. Former research and correlations of the tephras in the research area ...... 11 2.3. Volcanoes in the research area ...... 13 2.4. Tephras in other Antarctic lakes and marine sediments in the wind catchment area . . . 14 3. Materials and methods ...... 15 3.1. Pretreatment of samples ...... 15 3.2. Subsampling for grain size, grain and tephra identification, and chemical analysis ...... 16 3.2.1. General description of subsampling procedure ...... 16 3.2.2. Statistics ...... 16 3.2.3. Subsampling for chemical analysis ...... 17 3.2.3. Analysis by WDS, EDS and LA-ICP-MS ...... 17 3.2.3.1. Instruments and calculations ...... 17 3.2.3.2. Mounts and transferring of samples ...... 19 3.2.4. Step by step analyses of LA-ICP-MS-results ...... 20 4. Results ...... 22 4.1. Tephra horizon identification ...... 22 4.2. Chemical analysis - WDS followed by LA-ICP-MS, testing a method ...... 24 4.3. Chemical analysis - EDS ...... 34 4.3.1. Midge Lake ...... 34 4.3.2. Lake Boeckella ...... 35 4.3.3. Hidden Lake ...... 35 5. Discussion ...... 56 5.1. Measuring grain size and concentration of volcanogenic grains ...... 56 5.2. Identification of volcanogenic grains and tephra horizons ...... 57 5.2.1. Cryptotephras, statistics and background populations ...... 57 5.2.2. Volcanogenic mineral grains ...... 58 5.3. Chemical analysis ...... 59 5.3.1. General discussion ...... 59 5.3.2. WDS and LA-ICP-MS data ...... 60 5.3.2.1. General, problems ...... 60 5.3.2.2. Single grain analysis ...... 60 5.3.3. EDS data ...... 61 5.3.3.1. General ...... 61 5.3.3.2. Midge Lake ...... 62 5.3.3.3. Lake Boeckella and Hidden Lake ...... 62

5.3.3.4. FeO/MgO and SiO2 - alternative interpretations? ...... 63 5.3.3.5. Pretreatment of samples and spread of data ...... 64 5.4. Hypothetical age correlations from depth of tephra horizons ...... 65 6. Conclusions ...... 67 6.1. Current research ...... 67 6.2. Suggestions for future research ...... 68 7. Acknowledgments ...... 68 8. References ...... 69 9. Appendices ...... 77 Appendix 1. Grain size analysis, tephra horizon identification, and statistical analysis . . . . . 77 Appendix 2. Subsample description for WDS, LA-ICP-MS and EDS analysis ...... 84 Detailed description on how to mount grains for chemical analysis ...... 86 Appendix 3. Grouping of WDS-analysis-data in shards/minerals ...... 87 Appendix 4. Instruments/methods used in tephrochronology for chemical analysis ...... 92 Methods for chemical analyses ...... 92 Non-chemical methods to identify tephras ...... 94 Appendix 5. Examples of earlier published geochemistry data from tephras, mainly from the research area ...... 94 Deception Island, samples and age ...... 94 Published geochemistry analyses of volcanic eruptives ...... 95 Appendix 6. Different statistical methods used in tephrochronology work ...... 112

Supplementary material with raw data, in excel (CD) • Appendix 5. (Raw data for table A5:2 and table A5:3.) • EDS- final-after-recalc-CD. (All EDS-data, after conversion from atomic percent to weight percent.) • EDS-original-recalculated-1-26-CD. (Recalculation of EDS-data 1-26, from atomic percent to weight percent. Also, some short thoughts and discussions included.) • EDS-original-recalculated-27-89-CD. (Recalculation of EDS-data 1-26, from atomic percent to weight percent. Also, some short thoughts and discussions included.) • EPMA-190412-is-all-cd. (All original WDS-data, uncut.) • EPMA-EDS-publish-cd. (All data used for figs. 12-19.) • LA-ICP-MS-only-compare-mg-si-al-ti-CD. (Comparison of WDS to LA-ICP-MS, all data.) • LA-ICP-MS-original-publish-CD. (All data used in comparison of LA-ICP-MS-analysis.) • Midge Lake-1-calculations-CD. (All calculations of grains/g dry weight and statistics.) • Lake Boeckella-uppdaterad-OK-CD. (All calculations of grains/g dry weight and statistics.) • Hidden Lake-calculations-30samples-mats-original-CD. (All calculations of grains/g dry weight and statistics.) Finally, the word “tephromancy” refers to divination by the inspection of sacrificial ashes, requiring supernatural insight to foresee the future. David J. Lowe 2011 (

1. Introduction

1.1. Advances and problems of tephrochronology

1.1.1 General observations

Earth history, climate and land forms, are important parts of the areas of Quaternary geology and physical geography. To try to get all history in order, and to try to find out what happened and why something happened, to help us for future choices, everything has to be tied together in some way. Therefore it is necessary to find a method for binding scientific data together, a glue which everything else fits into. The subject of correlating volcanic eruptions, i.e. tephrochronology, may be often be that glue. Also, volcanic ash has become a hazard, not only for jet planes during eruptions, but also for general health care, as small volcanic glass particles are transported very far and easily get stuck in the lungs of animals and humans (Lowe 2011). In this last case the current research may help to trace wind paths for transport of small ash particles.

Tephrochronology is, as the name indicates, dating by the help of tephra, i.e. by volcanic eruptive fragments. Today, tephrochronology has become one of the most important methods of correlation of distant areas and finding isochronous strata, to knit everything together in the late Quaternary, a method better and less troubled by contextual and statistical limitations than radiometric dating (Pyne-O´Donnell 2010). Much of this research area is concerned with finding, identifying, correlating and dating volcanic ashes, also called tephras (other volcanic eruptives are also included under the label tephra, but in the current work we are mainly concerned with volcanic ashes). Volcanic ash is composed mainly of glasses (also called shards) and minerals (including quartz and feldspars), and a small amount of rock fragments (Nakagawa and Ohba 2002, Ohba and Nakagawa 2002, Dunbar and Kurbatov 2011). A review of the of the area of tephrochronology was published by Lowe (2011) and of tephrochronology in Antarctica by Smellie (1999a).

Ash flocculates in air and fall quicker to the ground than fluid dynamic models suggest, and most ash fall within a day of eruption (Rose and Durant 2009). The 31-62 µm size fraction become proportionally dominant in distal regions (Rose and Durant 2009). Ash also sink quickly in water, as density currents or floccules (Macquaker et al. 2007, Schieber et al. 2007), with the highest rate recorded as 3730 m within three days (Lowe 2011).

The central observation, which the research area of tephrochronology is built upon, is the fact that different magmas and, hence, ashes, often display individual chemical characteristics, which make correlations between different remote sites possible. This holds especially for REE:s (rare earth minerals, i.e. the 15 lanthanides and scandium and yttrium) and other trace elements in volcanic glass shards (Shane and Froggatt 1994, Allan et al. 2008, Kraus and Kurbatov 2010), but minerals which have solidified in the magma before

1 the eruption may also be used (Sarna-Wojcicki 2000, Nakagawa and Ohba 2002). As volcanic ashes are transported very long distances and settle quickly, they form large isochronous time planes. It is not uncommon with transport distances of 6000 km of small quantities (Narcisi et al. 2005). Some ashes are transported 5000 km in a matter of days, and some even 12 000 km (Lowe 2011). Tephras in Antarctica are thought to have been transported c. 4000 km from volcanoes on Deception Island and other South Shetland Islands (which is especially relevant for the current research), or e.g. 6000 km from the Andes (Narcisi et al. 2005).

Silicic eruptions are often more explosive and generate much more fine ash than basaltic eruptions (Sarna-Wojcicki 2000, Pearce et al. 2007, Durant and Rose 2009), which is especially relevant if you find silicic tephras in places where there are no known volcanoes with acidic eruptions nearby. The latter is the case when tracing bimodal eruptions from Iceland, where the acidic phase can be traced over much larger portions of Europe than the basaltic phase (Lane et al. 2012, see also Tomlinson et al. 2010). Also, the basaltic phase may be more dense than the silicic phase (Lane et al. 2012).

1.1.2. Difficulties in tephrochronology work

Sometimes, however, the difficulties in tephrochronology are numerous, and it may be felt as if you are on a “deception island”. But the area of tephrochronology is far from as bad as the area of “tephromancy”. One major problem is that researchers use different methods of analyses and analyse different or not specified material, e.g. bulk samples (which is problematic because of possible contamination from the country rock, and that the chemical content may vary with distance; Pearce et al. 2007), unspecified shards, basaltic (usually brown or black) glass or silicic/acidic glass (e.g. Hodgson et al. 1998, Fretzdorff and Smellie 2002, Blockley et al. 2005, Lee et al. 2007 and pers. comm. David J. Lowe 2011). Bulk sediment samples, which may contain indigenous and extraneous mineral grains, are known to be less siliceous than their corresponding glass shard fraction (Fretzdorff and Smellie 2002). Hence, the area of tephrochronology has not been “standardized”. This made e.g. six tephrochronologists to reanalyse their earlier c. 10 papers, and other researchers former published data, in a reinterpretation of a tephra in Beringia to be mono-eruptive and not from many eruptions (Preece et al. 2011). Therefore it is important to report all analytical conditions and try to follow more recent “standard” methods and report in detail which methods are used, because otherwise the results may sometimes be more dependent on laboratory procedures than real data (Hayward 2012, Lowe 2011, Kraus et al. in press 2013).

An even bigger problem then the laboratory procedure may be the identification and interpretation of tephras, especially in marine and lake sediments. Small size of volcanic eruptions, wind directions, winter conditions and other environmental influences, may hamper the possibility to correlate different tephras. Many tephras are invisible for the naked eye, and these are called cryptotephras (Lowe 2011). Hence, Sarna-Wojcicki (2000) published a generalized flow chart for tephra identification, with more complicated and expensive methods to use if tephras could not be recorded easily. For example, in marine sediments at a depth of 3290 m below the sea surface, nearly half of 70 tephras were interpreted to be reworked and repeated, with up to 8 meters of sediment between the first and second occurrence of the same tephra. And e.g. in three cores within a few hundred meters distance from eachother only eight tephras are present in all three cores, and 22 of c. 37 tephras in one core are preserved only in this core (Allan et al.2008). An observation that

2 many tephra horizons are detected in lake sediments but few of these same horizons are recovered in marine sediments (Hodgson et al. 1998, Moreton and Smellie 1998), may indicate that many tephras in lakes may be from the same eruption but have been reworked by e.g. rainwater which have transported tephras first deposited on land. Tephra deposition may be patchy on a scale of meters, repeatedly reworked, and sometimes is lagging for hundreds or even thousands of years, which make the method less optimistic in at least some cases - more so in arctic climate because of catchment traps in e.g. snow, lake ice or glaciers (Davies et al. 2007, Lee et al. 2007, Hillenbrand et al. 2008, Rose and Durant 2009, Pyne- O´Donnell 2010, Preece et al. 2011, Lowe 2011, Kylander et al. 2011). Some researchers believe that glass shards have sunk downward 30 cm (or “3000 years”) in organic-rich sediments and stopped in a more dense layer, with the appearance of being a tephra layer (Enache and Cumming 2006; see also Davies et al. 2007).

In arctic climates there is none or little vegetation which bind the ashes to the ground. Therefore ashes can be transported and accumulate in small e.g. bedrock or glacial depressions, or within permanent snow during many years (e.g. Davies et al. 2007). These accumulations may be emptied en masse during a violent rain storm or a temperature maxima followed by heavy melting, by overflowing of running water, and then followed by deposition of the material over large areas of the bottom of a small lake. As there is often nothing in arctic climate lakes which bind the sediment to the lake bottoms, and sediments have not accumulated and stabilized during a long time period after deglaciation of the area, the sediments are often unstable. Hence, many tephras in lake sediments on King George Island, in the Antarctic Peninsula area, are believed to be reworked in gravity flows (Lee et al. 2007), and gravity flow deposits have been observed in the sediment cores from the Antarctic lakes of the current research (pers. com. Rolf Zale 2012). There are also many other problems of correlation (Dunbar and Kurbatov 2011, Lowe 2011).

In small lakes, similar to those analysed in the current research in the Antarctic Peninsula area, but in Scotland, systematic coring and tephrochronology has been conducted for more than 30 years (Pyne-O´Donnell 2010). It was found that the supposed areal continuity of tephras was exaggerated. The tephra deposits are dependent of inlet, outlet, catchment area, depth, morphometry, seasonal ice coverage etc. Even in the deepest parts of the lakes the tephra distribution may be patchy. In three small lakes, six different tephra layers were located, but only three of them were detected in all lakes. In one lake, sized c. 180x125 m, with a large catchment area (c.285:1), three inlets and one outlet, an ash layer was detected which was not observed in cores meters away. Three different tephra layers were situated in somewhat different places of the lake, however they were thickest close to the inlet and there were few shards at the far margins of the lake. A smaller lake, sized c. 120x45 m, with no inlets or outlets, with a catchment area not much larger than the lake itself, showed most shards in the deepest parts. In a third lake, sized c. 80x80 m, with catchment area c. 25:1, with two possible paleoinlets and a single outlet, most of the tephra was deposited at the inlets (Pyne-O´Donnell 2010). This research from Scotland underlines that deposits of volcanic ash have similar problems of interpretation as all kinds of sediments. It is not a “one time observation, one explanation” subject.

Other problems with interpretations of tephras concerns that eruptives a) sometimes are believed to have similar chemical composition from the same, or maybe even different, volcanoes in the same area, for up to tens of thousands of years b) sometimes are heterogenous or bimodal and hence the chemical composition changes during the same

3 eruption c) sometimes display the same chemical signature from different volcanoes, and d) sometimes may change chemical signature even during aeolian transport (Björck and Zale 1996a, Moreton and Smellie 1998, Narcisi et al. 2005, Kuehn and Foit Jr. 2006, Lee et al. 2007, Allan et al. 2008, Hillenbrand et al. 2008, Lowe 2008, Ukstins Peate et al. 2008, Tomlinson et al. 2010, Lowe 2011, Thornalley et al. 2011, Housley et al. 2012, Lane et al. 2012). However, usually it is believed that the chemical composition should not vary with distance from the source (Hodgson et al. 1998). As an example relevant to research in the Antarctic Peninsula area, considering the large variations in F, B, K and P in lavas from Deception Island, Smellie et al. (1992) speculated about open-system fractionation and other means of mixing with “foreign” material. As a trigger for one eruption, influx of a compositionally different magma was suggested, to explain differences in chemical composition of the eruptives (Smellie 2001). See similar explanations of fractionation of magmas in volcanoes in the research area, by Weaver et al. (1979), Fisk (1990) and Keller et al. (1992), in Iceland by Lane et al. (2012) and in other areas by Ukstins Peate et al. (2008). The heterogeneity within single eruptions, where the differences in element ratios is high both in single eruptions and within single grains, is “crowned” with one single grain smaller than 1 mm which display 85% of the total difference in SiO2 from that single eruption - a variation in SiO2-content from 59.2-75.3% inside that single grain (i.e. an eruption traced in the Oligocene of Yemen and Ethiopia, Ukstins Peate et al. 2008).

1.1.3. The current research

The aim of the current research is to evaluate the methods of tephrochronology, as described above and below, to find a reliable method to identify and correlate volcanic tephra horizons in piston cores from lacustrine sediments in the Antarctic Peninsula. The main methods for physical identification and chemical analysis of tephra will be used and evaluated. A time series of c. 500 years, in three small Antarctic lakes, is analysed for tephra horizons and chemical compositions, for possible correlations.

1.2. Identification of shards and chemical analyses of ashes

1.2.1. Optical polarizing microscope

Identification of glass shards is often done with a polarizing microscope. If volcanogenic grains are found in glaciers, the simple method of just melting the ice and collecting a sample can be used. If ashes are found in other environments, e.g. lakes, where there are many physical influences, any collected sample may be a mixture of all kinds of grains from different environments. This is especially relevant where there are active glaciers nearby which crush and grind bedrock and transport rock material, and there is no or little vegetation which bind the ashes and other sediments. Hence, especially in an arctic climate lake environment the methods for identification of volcanic matter is not straightforward. If the tephras are invisible for the naked eye, they are classified as cryptotephras (Davies et al. 2007, Lowe 2011). Also, microscopic sized grains of many origins may have similar physical appearance. Identification by optical polarizing microscope also is not 100% accurate, because some shards, and mineral grains of e.g. quartz and feldspars, have similar optical appearance under single and crossed polarizers.

X-ray fluorescence (XRF) is a method which may be used to quickly find layers of tephra. Usually if there is more than 850 shards/cm3, tephras are detected, but sometimes as little as

4 60 shards/cm3 may indicate a tephra horizon even if there is none (Kylander et al. 2011), and therefore it is still necessary with hand counting of grains.

Magnetic susceptibility (e.g. HIRM/SIRM) is sometimes used to try to find tephras (Björck et al. 1991a, 1993), but magnetic methods are not always a good indicator of tephras, because cross-matching with optical methods do not always conform (Hodgson et al. 1998).

Grain size and grain concentration analysis of volcanic ashes is measured in either shards/g dry weight, shards/0.5g dry weight, shards/g wet weight, shards/cm3, or shards/total grains (Davies et al. 2007, Lowe 2011). The units are the same for volcanogenic mineral grains.

1.2.2. Analyses of major, minor and trace elements

1.2.2.1 General description of instruments used in tephrochronology

There are many methods for analysing grains for chemical elements, but lately a few methods have become more popular (see links to descriptions of the methods in Appendix 4). A SEM (scanning electron microscope) with EPMA (electron probe microanalysis) WDS (wavelength dispersive spectroscopy = measuring X-rays from elements) is the “cornerstone technique” of analysing major elements, in correlation work (Lowe 2011, p. 123). Otherwise a SEM with EPMA EDS (energy dispersive spectroscopy = an alternative method of measuring X-rays from elements) can be used. (Hereafter only the labels WDS and EDS will be used, except if this is not important for the discussion.)

The analysis of major elements should in ideal cases be followed by LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry = evaporating and ionizing the samples and collecting and analysing the generated gases) on the same samples, for minor/trace elements, which is an accurate, simple and rapid method often applied to silicic glass shards (Pearce et al. 2007, Li et al. 2010, Lowe 2011, Jenner and O'Neil 2012a). From a single glass shard, 40 µm in diameter, 30 trace elements can be identified by LA-ICP-MS in between two seconds and three minutes, and with all technical procedures included, c. 150- 200 grains may be analysed during one day (Dussubieux et al. 2009, Lowe 2011, Pearce et al. 2011). For other methods of chemical analysis, e.g. a large sample size is needed, they are problematic if e.g. zircon occur, they can only analyse a few trace elements, or they are more expensive and slower than LA-ICP-MS (Pearce et al. 2007, Li et al. 2010, Lowe 2011, Pearce et al. 2011, and Appendix 4). LA-ICP-MS is more widely available, and problems with the method are known and can be avoided (Jenner and O´Neill 2012b). The main shortcoming of LA-ICP-MS is that a major absolute element ratio needs to be known in the material studied, before an exact analysis can be done.

In 1979 c. 50 elements were tested for, usually 40 were detected, and 18-20 were possible to use in tephrochronological correlation (Sarna-Wojcicki et al. 1979). Today many trace element “working concentrations” are available for LA-ICP-MS (Lowe 2011). Pearce et al. (1997 ) compiled data for 58 elements (data from 60 published works), and this was updated by Jochum et al. (2011) who published values for c. 70 elements as reference/certified values. Perkins et al. (1997) described the development of LA-ICP-MS, and Pearce et al. (2007, 2011) updated the information.

In the LA-ICP-MS the necessary major absolute element ratio is used as internal standard, to

5 turn the raw data into rates, commonly Si-29 or Ca-43. This ratio has to be known from analysis of major elements, from e.g. EPMA. If Ca is less then 1%, Ca-43 can not be used for calibration, and, Ca is not common in acidic ashes. Samples from Deception Island, the probable source of most of the tephras in the research area, are mostly basic (basaltic), but some may be acidic (rhyolitic) - as is seen from the literature from the area. Therefore Si-29 often is a better choice. But, sometimes Si-29 is detector saturated, which make some data unusable (Pearce et al. 2007 ). However, relative element ratios can still be measured, if LA- ICP-MS is the only instrument used (with no former reading of major elements by EPMA), or if the detector is saturated, without knowledge of the absolute content of any element.

1.2.2.2. Instrument limitations

There have earlier been great differences between different instruments, when analysing produced standards (NIST), e.g. for some elements 50-400% for different methods and laboratories (Pearce et al. 1997, and Appendix 4). So, it is not a good suggestion to make too much of correlations from old data. Dissimilarity between different instruments may still be up to 110%, for low abundance elements (Kuehn et al. 2011). Interlaboratory variation with LA-ICP-MS can still be approximately 20% in relative deviation for most elements (Dussubieux et al. 2009). This is a problem when comparing data from different researchers/laboratories. Interlaboratory variation is more or much more than 30% in relative deviation for P, Fe, As, In, Sn, Sb, Cs and Pb (Dussubieux et al. 2009). There are often large differences between ICP-MS (the method for analysing samples turned into plasma, but using more different and more complicated methods for turning samples into plasma than a laser in the LA-ICP-MS) and WDS, especially for the major element oxides which have high melting points, i.e. Mg and Ca. Mg-oxides often is 2-3 times (i.e. up to c. 300% more compared to the lowest value) higher with ICP-MS (bulk tephra) than with WDS (volcanic glass), and for Ca the ratio is often doubled (Kraus et al. 2013, in press, compare values in their supplementary material). Also, Mg-oxides and heavier oxides of trace elements with high melting point (e.g. all lanthanide oxides have almost similar melting point as Ca- and Mg-oxides, and the actinide oxides of Th and U have even higher melting points; Schneider 1963, Hlaváè et al. 1982, Carniglia and Barna 1992), vary much more than the other major elements (often c. 20%), when comparing tephras with other volcanic material (Kraus et al. 2013, in press, compare values in their supplementary material). It is suggested that more research has to be conducted on the importance of melting points of major and trace elements, and their connection to different eruptive and fractional processes (e.g. incompatible elements like lanthanides are more common in low temperature melts) in the area of tephrochronology (e.g. Goldsmith and Peterson 1990, Gualda et al. 2012, Nelson 2012). But, even though there are still many problems, as more research is done and methods are approving, most differences with LA-ICP-MS from NIST-standards are within 10% (Jenner and O´Neill 2012b).

Also, it is necessary that the analytical methods used (e.g. WDS) will not dissolve Na, which commonly is a problem (Kuehn and Foit Jr. 2006, Hayward 2012, Kuehn et al. 2011, Lowe 2011). If a small electron beam is used, it is often not a problem (Kuehn et al. 2011, Lowe 2011).

1.2.2.3. Necessary data for chemical analyses

When conducting element analysis, sometimes Fe2O3 (total) is calculated, but otherwise FeO

6 (total), and, hence, there are small differences in the results (e.g. compare samples in Fretzdorff and Smellie 2002 to the same samples in Smellie and Millar 2002). A normalisation value between Fe2O3 (t) and FeO (t) is given by Weaver et al. (1979).

The 100-200 µm grain size class is best for WDS/LA-ICP-MS (Stokes et al. 1992, Knott 2007, pers. comm. Dmitry Kuzmin 2012). If only grains 25-80 µm are used it is a high possibility that the preparation methods for the samples have removed both silica and other major and minor elements (Blockley et al. 2005). It is also easier to sample and prepare larger grains. However, recent developments in LA-ICP-MS technique, make it sometimes possible to easy analyse grains as small as 20-40 µm (Pearce et al. 2007, Pearce et al. 2011, Lowe 2011). If shards are as small as 5-10 µm, SIMS (secondary ionization mass spectrometry), or in certain cases LA-ICP-MS, may be used (Lowe 2011, Pearce et al. 2011).

To arrive at a statistically good result, 50 shards per sample may have to be analysed, because of heterogeneities in some tephras, but usually only 15-20 (Lowe 2011).

For WDS the grains have to be mounted in epoxy and polished, for LA-ICP-MS no polishing is needed even though it is important that the grain surface is visible, and for EDS only a double adhesive tape is necessary. EDS is the method which has lowest accuracy (readings less than one atomic percent are uncertain, and readings less than 0.5 atomic percent are not statistically significant and ought to be interpreted as absence of that element; pers. comm. Per Hörstedt 2012), and some researchers even think that EDS may only be used for recognizing different elements (Science Education Resource Center at Carleton College, June 2012). But with the ratios of elements which are measured in tephrochronology, there is no significant difference with EFS for most elements compared to WDS (Kuehn et al. 2011). However, in the current work Mn was never measured with EDS, because it is always less then 0.5 atomic percent. (“Atomic percent” is similar to ppm, but measured in percent, but it only compares the “part” of the elements which are measured, and not all elements in the sample. E.g. the oxygen “part” is not taken into consideration because it is not measured.)

In Kuehn et al. (2011) there is a summary of recommendations to follow for analytical work and for publication of data.

1.2.3. What elements are analysed?

1.2.3.1. Major elements

Almost all researchers analyse for the following major elements, with EPMA: Na, Mg, Al, Si, P, K, Ca, Ti, Mn and Fe. Si, Al and Mn does not vary very much in Deception Island, which is the volcano that is best analysed and the probable source of most recent ashes in the research area, but these elements should always be included to help standardize the methodology of tephrochronology.

1.2.3.2. Minor/trace elements

In lavas and other eruptives (excluding tephras) from Deception Island, approximately dated from the last c. 500 yr, the following minor/trace elements show large differences: a) V, Cr, Ni, Cu, Rb, Zr, Ba and La display more than 50% systematic differences, compared to the lowest content recorded.

7 b) Zn, Sr, Y, Nb, Ce, Nd and Th show more than 20% difference, but not a systematic 50% difference. c) Ga and Pb display smaller difference than 20%.

If we consider the ratios of elements in tephras from volcanoes in the research area, which are used to separate different volcanoes, Zr/Hf, Nb/Y, Th/Yb, Ta/Yb, Sr/Y, Th/Nb and Ba/Th are important (Kraus and Kurbatov 2010, Kraus et al. in press 2013).

Sc, Cs, La, Hf, Ta, Ce, Sm, Eu, Tb, Dy, Yb, Lu and U are suggested as more important by tephrochronology researchers Nelia W. Dunbar (pers. comm. 2011) and Elmira Wan (pers. comm. 2011).

The following REE:s have been used by many different researchers: Sc, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Lu (e.g. Shane and Froggatt 1994, Knott et al. 2007, Allan et al. 2008, Ukstins Peate et al. 2008, Housley et al. 2012, Lane et al. 2012). Other common elements used are Pb and U (Allan et al. 2008, Ukstins Peate et al. 2008, Housley et al. 2012, Lane et al. 2012).

2. Area description and earlier work

2.1. Geography of lakes and environment in the research area

Three small lakes in the Antarctic Peninsula area have been chosen for the current research, and have been cored for e.g. tephrochronology analysis. These are Midge Lake on Byers Peninsula (which is the westernmost part of Livingston Island, South Shetland Islands, northwest of the Antarctic Peninsula; Björck et al. 1993, Björck and Zale 1996a, López- Martínez et al. 1996b, Thomson and López-Martínez 1996) (figs. 1 and 2), Lake Boeckella (Hope Bay) close to the tip of the northern Antarctic Peninsula (Zale and Karlén 1989) (figs. 1 and 3), and Hidden Lake on James Ross Island (just east of the northern part of the Antarctic Peninsula; Zale and Karlén 1989) (figs. 1 and 3).

Earlier work in the area has been conducted by many researchers (see documentation in this paper, and reviews in Smellie 1999a, Kraus and Kurbatov 2010, Lowe 2011 and Kraus et al. in press 2013). There has been a discussion concerning the Holocene glaciation story on Byers Peninsula, which is of importance when interpreting deposition and correlation of tephras, but it appears that the interpretation by Björck et al. (1991a, 1991b), with a warmer climate since c. 4000 yr BP, is best validated (Lee et al. 2007).

Midge Lake is the deepest lake on Byers Peninsula. It is sized 587x112 m (50-65 000 m2 ), 9 m deep, and is surrounded by a rather steep shore, c. 20 m high. The basement is made up of a mix of late Paleozoic to recent eruptives and sedimentary bedrock, at the edge of an intrusive body (Smellie et al. 1995, López-Martínez et al. 1996c, López-Martínez et al. 1996d, Hodgson et al. 1998). It is next to the drainage divide and, hence, has a catchment area not much bigger than the lake (López-Martínez et al. 1996d). It has no inlet but one outlet (Björck et al. 1991b). There is permafrost in the area, but not much evidence of glacigenic erosion and deposition (López-Martínez et al. 1996d, Serrano et al. 1996). The sedimentation rate in the lake is low.

8 Fig. 1 . The research area. The box shows By ers Peninsula, Liv ingston Island, with Midge Lake (see fig. 2). Upper, right star on Trinity Peninsula is next to Hope Bay with Lake Boeckella (fig. 3). Lower star is James Ross Island, with Hidden Lake just south of the star, outside of picture (fig. 3). (Map from SCAR 201 2.)

Fig. 2. The research area, By ers Peninsula, Liv ingston island, with the small Midge Lake (black, formed like a banana) in the middle of the picture (see arrow). (Map from SCAR 201 2.)

9 Fig. 3. Volcanoes referred to in the text by Kraus et al. (201 3, in press) and used in correlations in the current research, and the lakes sampled in the current research. 1 ) Bransfield Island (no samples from v olcanoes from this island hav e been analy sed). 2. Sail Rock. 3) Deception Island. 4) Rezen Peak. 5) Gleaner Heights. 6) Edinburgh Hill. 7 ) Inott Point. 8) Penguin Island. 9) Melv ille Peak. 1 0) Bridgeman Island. 1 1 ) Cape Purv is v olcano. 1 2) Paulet Island. 1 3) Seal Nunataks. ML = Midge Lake on By ers Peninsula. LB = Lake Boeckella in Hope Bay /Esperanza base. HL = Hidden Lake.

Lake Boeckella, 0.12 km2, 9 m deep, is fed by melt water from two nearby glaciers (the closest within 100 m), in a small ice free area of a few square kilometers, in Hope Bay. The lake has one outlet. The area around the lake is rather flat (Zale and Karlén 1989, Zale 1994b, Birkenmajer and Ociepa 2008). The bedrock is including sandstone and eruptives (Birkenmajer and Ociepa 2008). The sedimentation rate in the lake is high.

Hidden Lake on James Ross Island, ca 1 km from Prince Gustav Channel, Weddel Sea, is 2.4 km long, with one outlet. Surrounding bedrock includes sandstones and volcanics (Ineson et al. 1986). In the early 80-ies permanent ice was touching the lake shores on two sides (Ineson et al. 1986). There are layers of till, which are interpreted to be ice-rafted, within the lake sediments (Zale and Karlén 1989). Hence, there is a good chance of recent contamination in the lake, from the surroundings. A warmer climate is registered in this

10 eastern part of the Antarctic Peninsula since c. 4000 yr BP, in accordance with the climatic history of Byers Peninsula (Björck et al. 1996b). The sedimentation rate in the lake is lower than in Lake Boeckella but higher than in Midge Lake (see Appendix 1).

Midge Lake is too far to the northeast to be in the general wind direction from Deception Island, but during local wind changes ashes may reach Byers Peninsula. Both Lake Boeckella and Hidden Lake are in the general wind direction from the volcano which have the only observed large recent eruptions, Deception Island, but they are c. 200 km away from the volcano (Björck et al. 1991a).

2.2. Former research and correlations of the tephras in the research area

In the Antarctic Peninsula area Björck and others have dated and correlated 14 tephra horizons by C-14 and magnetism (HIRM and SIRM), but because of the uncertainties in the C-14-ages (only 19 out of 30 dates were considered reliable) more correlations need to be done (Björck et al. 1991a, Björck and Zale 1996a, Zale 1994a, Gibson and Zale 2006). Most correlations and dating of tephras were made by an interpolated sedimentation curve (e.g. Björck et al. 1991a). In total 23 tephra layers were recorded from three Byers Peninsula lakes - Midge Lake, “Chester Cone Lake” and “Lake Åsa” (table 1). At Byers Peninsula five main “tephra zones” (corresponding to AP2, 3, 5, 10-12 and 14), compromising seven different tephra horizons (AP2, 3, 5, 10, 11, 12 and 14), two of them repeated (AP3 and AP5), were distinguished. But most tephra horizons from other areas close by where not found in the Byers Peninsula lakes, and no tephra horizons were identified in Byers Peninsula, Lake Boeckella or Hidden Lake, from the recent eruptions from Deception Island in 1842, 1912- 1917, 1967, 1969 and 1970 (Björck et al. 1991a). One reason why tephra from these most recent eruptions were not found on Byers Peninsula (Björck et al. 1991a), but in other places on Livingston Island (Pallàs et al. 2001), could be from miscorrelation rising from the C-14- dating problems (Björck et al. 1991a, Björck et al. 1993, Björck and Zale 1996a, Björck et al. 1996a, Björck and Wohlfarth 2001, Zale and Karlén 1989, Zale 1994a, Gibson and Zale 2006, Lowe 2008) or, of course, non-deposition in the area because of different wind directions, or just that there was no deposition of tephra at the points were coring was done (e.g. compare to small lakes in Scotland, above, Pyne-O´Donnell 2010). The latter interpretation is strengthened because Hodgson et al. (1998) recorded two tephras which they considered to be from more recent eruptions, while these two tephra horizons were not detected by the naked eye or magnetic methods in the two cores sampled c. 10-20 meters from eachother by Rolf Zale (pers. comm. 2012). The latter two horizons may be cryptotephras (see Results and Discussion in this work).

Midge Lake has eight identified tephra horizons, whereof one “acidic” (table 1) (Björck et al. 1991a, Björck et al. 1991b, Hodgson et al. 1998). Those relevant to the current research are only the three highest tephras, which are younger than 500 years. 14C-dating of mossrich sediments associated with four of these tephras is used as the guide of correlation in this area (Björck et al. 1991b, also referred to by e.g. Hodgson et al. 1998).

11 Table 1 . Tephra horizon chronology and correlations in the Antarctic Peninsula area. X is “tephra horizon is present”, multiple X:es is that the tephra is interpreted as repeated. Tephras y ounger than AP1 were not recorded when this chronology was constructed. The 20 tephra lay ers in Hidden Lake, Lake Boeckella and Walker Point are interpreted from magnetism: HIRM = high isothermal remanent magnetization (indicator of hematite and goethite), and SIRM = saturation remanent magnetization. (A = Hodgson et al. 1 998. B = Björck et al. 1 991 a. C = Björck and Zale 1 996a. D = Björck et al. 1 993. E = Björck et al. 1 991 c.) Age, C-1 4 BP Tephra Midge Midge Lake Bo- Hidden Chester Lake Åsa Elepha. and appr. AD horizon Lake (A) Lake (A, eckella Lake (B) Cone (B, D) Isl., Wal- cal. y ears B, C) (B) Lake (B) ker P. (B, E)

-20/1 967 - X, 2-3 cm 1 97 0? acidic

33-1 1 0/1 842 X, 3-4 cm or 1 91 2-1 91 7 ?

250/1 7 00 AP1 X, 1 2 cm

450/1 500 AP2 X, 8-9 cm X, 7 cm X X, 28 cm X X

7 50- AP3 X, 1 5-1 6 X, 1 2 cm XX X XX 800/1 200 cm

1 050/900 AP4 X X

1 250- AP5 X, 21 -22 X, 20 cm X X XXX 1 400/7 00 cm

1 850/1 00 AP6 X X X

2050 AP7 X X X

2200 AP8 X

2500 AP9 X X X

2630 AP1 0 X X X

27 1 0 AP1 1 X X X

27 60 AP1 2 X X X

3500 AP1 3 X

47 50 AP1 4 X X X

In Midge Lake and Lake Boeckella AP2 is registered (Björck et al. 1991a, Björck and Zale 1996a). In Hidden Lake piston core, tephra layers are interpreted and correlated with AP1 (200 years) and AP2 (450 years) (table 1) (Björck et al. 1991a). There is no published chemical data from Hidden Lake, but the recorded tephras are correlated with other lakes (Björck et al. 1991a). One tephra layer is recorded as from c. 1700 AD in Hidden Lake, but the most powerful eruption is dated to c. 1641 by ice core chronology and is the only visible eruption recorded in the glacier on James Ross Island. This 1641 eruption is correlated with a tephra in the South Pole Station ice core and other tephras at Plateau Remote, Talos Dome and Amundsenisen in Antarctica (Aristarain and Delmas 1998, Palais et el. 1989, Kraus and Kurbatov 2010). This eruption is believed to be from Deception Island, but there is no known/recorded data of any eruption at Deception Island which corresponds to 1641.

Earlier attempts to correlate Lake Boeckella and Hidden Lake, based on times series and periodicity analysis, has failed (Zale and Karlén 1989).

12 2.3. Volcanoes in the research area

Most or all tephra layers in the research area probably erupted from Deception Island (fig. 3), which is active today (Björck et al. 1991a). The record of eruptions on Deception Island are dated from max 100 ka to recent, with many eruptions during the last c. 500 years, as documented by Orheim (1972), Pallàs et al. (2001), Smellie (2001, 2002a, 2002c), and Smellie and Millar (2002). (See Appendix 5 for more details.)

Deception Island is c. 45 km south-east from Midge Lake, Byers Peninsula, but not in the wind direction of Byers Peninsula (López-Martínez et al. 1996a, Pallàs et al. 2001). The recent 1967 and 1969 eruptions were very small, and the wind direction was from the west or north, and much ashes from these eruptions could possible not have reached many other islands (Smellie 2002b). However, a small change in wind direction distributed some ashes from the 1967 eruption on Livingston Island (Pallàs et al. 2001). The latest, 1970, eruption was more violent, but even if wind direction was from the south, ashes probably could not have reached Byers Peninsula. But the part of Livingston Island, which is nearest from Deception Island, i.e. Hurd Peninsula, and King George Island further east, received ashfall (fig. 3) (Pallàs et al. 2001).

Other volcanoes or volcanic centers in the research area are Bridgeman Island, Seal Nunataks on Lindenberg and Robertson Island, volcanoes on Livingston Island (Gleaner Heights, Edinburgh Hill, Rezen Peak and Inott Point), Penguin Island, Sail Rock, Brabant Island, Melville Peak and Low Head (the last one dated to 24 Ma) on King George Island, numerous small volcanic centers on Livingston and Greenwich Islands etc., and several submarine seamounts (including Hook Ridge) (Björck et al. 1991a, Smellie 1999b, Fretzdorff and Smellie 2002, Kraus and Kurbatov 2010). Most of these have been active in Holocene or even historical or recent time, and some are still slightly active - e.g. Bridgeman Island had active fumaroles between 1821-1850 and volcanic activity has been observed on a few occasions on Seal Nunataks (Weaver et al. 1979, Kraus and Kurbatov 2010, Kraus et al. in press 2013). Further on, there are many small volcanic centers in the James Ross Island Volcanic Group, including possible recent (< several ka) basaltic volcanos at James Ross Island (e.g. Eugenia, Marina and Elba volcanoes), and at Cape Purvis and Paulet Island, c. 80 km north of James Ross Island (Smellie 1999b, Smellie et al. 2006, Smellie et al. 2008, Kraus and Kurbatov 2010, Kraus et al. in press 2013). The youthfulness of volcanoes in the area is indicated by the observation that all samples which Kraus and Kurbatov collected from ten Quaternary volcanoes in the Antarctic Peninsula area, except from the older parts of Deception Island, are fresh, with a chemical alteration close to zero (Kraus and Kurbatov 2010, Kraus et al. in press 2013). Hence, even if most of the eruptions have not been observed, the data indicate very recent eruptions.

Up until June 2012 no geochemical data from tephras sampled at the volcanoes in the Antarctic Peninsula area had yet been published, but only from other eruptives like lava and scoria (e.g. Kraus and Kurbatov 2010, Kraus et al. in press 2013). But some comparisons where tephra is referred to have been published, e.g. see Pallàs et al. (2001). However, many tephras in ice cores, lakes, glaciers etc., which have been correlated with Deception Island, have been recorded, and many more will be published (e.g. Kraus and Kurbatov 2010, pers. comm. J. L. Smellie 2011, Kraus et al. in press 2013). E.g. different eruptions on Deception Island have been chemically correlated with different tephra layers in glaciers in the Hurd Peninsula area (fig. 3), southernmost Livingston Island, the land area closest to the volcano,

13 just northeast of Deception Island (Pallàs et al. 2001).

Most of the volcanoes in the research area have been chemically distinguished, especially if minor/trace elements are used (Kraus and Kurbatov 2010). Kraus et al. (2013, in press) constructed a “logistics” tree to follow, when trying to identify tephras from different volcanoes in the area. E.g., volcanoes in the northern Bransfield Strait (Penguin Island, Melville Peak and Bridgeman Island) have lower Zr/Hf than all other volcanoes in the area. And, Nb/Y ratios are more than one order of magnitude higher from volcanoes Paulet Island and Cape Purvis (situated east of the Antarctic Peninsula) compared to the volcanoes which are situated west of the Antarctic Peninsula. Th/Yb, Ta/Yb and more element ratios are also higher east of the Antarctic Peninsula. Paulet Island display high Sr-content, and also higher Sr/Y-ratios than its neighbour Cape Purvis. Melville Peak and Penguin Island show highest Mg-content. Sail Rock and Bridgeman Island exhibit high Al-contents. Melville Peak and Bridgeman Island show lower Nb/Y and higher Th/Nb than Deception Island, Penguin Island and Sail Rock. Sail Rock displays higher Th/Yb than Deception Island, and Sail Rock and Melville Peak display lower Ba/Th than Penguin Island.

Deception Island displays the most geochemical compositional spread of all Quaternary volcanoes in the area (Kraus and Kurbatov 2010). Some tephras interpreted to be from Deception Island are believed to be from a bimodal eruption, i.e. the tephras display a thorough mix of brown basaltic and clear siliceous glass and no or few shards with an intermediate chemical composition (Moreton and Smellie 1998). Influx of a compositionally different magma was suggested, to explain differences in chemical composition of some eruptives (Smellie 2001). But, even small eruptions show large compositional ranges, indicating zoned or multiple magmas (Smellie 2002a). But, Deception Island also has erupted magmas with similar compositions at different times in its history, so it is difficult to correlate tephras with special eruptions based only on major elements (Fretzdorff and Smellie 2002).

Another source of tephra in the area is Marie Byrd Land (MBL), c. 3000 km from Byers Peninsula. Even if the wind direction is correct for transporting ash from MBL to Byers Peninsula, tephra layers on Byers Peninsula are sometimes easy visible (up to 20 mm thick, Björck et al. 1991a), so it appears that these can not have been far transported. However, half way between MBL and Byers Peninsula the shards from MBL are ranging from 35 µm to 620 µm, and within 200 km of Byers Peninsula there are still many shards ranging from 32-160 µm (mean grain size is 91 µm and max grain size is 191 µm). But, these deposits are believed to have an age of 100-200 ka, and are interpreted to be from MIS (Marine Isotope Stage) 5-6 (Hillenbrand et al. 2008).

2.4. Tephras in other Antarctic lakes and marine sediments in the wind catchment area

Tephras on King George Island, were divided into basaltic (c. 80%) and silicic glass (c. 20%), after chemical analyses. These two groups of shards were compared within and between eachother, and were believed to be mixed from different volcanoes. It was little variation within the groups, but large variation between the groups. The silicic grains and c. 10% of the basaltic grains have chemical compositions which could not be correlated well with any known source volcano (Lee et al. 2007). The remaining tephras are believed to be from Deception Island, even though the statistical SC-values (Similarity Coefficient) are low - the

14 latter is interpreted as a product of contamination/mixing with ashes from other volcanoes (Lee et al. 2007). But, researchers in the area are discussing a bimodal eruption from Deception Island (Moreton and Smellie 1998, Fretzdorff and Smellie 2002), and some eruptives from Deception Island have high SiO2-content (e.g. Weaver et al. 1979), and acidic ash is transported further, and sometimes thousands of kilometers further, than basaltic ash (Lane et al. 2012); in the case of King George Island it is only a distance of c. 130 km if the source is Deception Island. We may therefore speculate that the mixed tephras on King George Island are at least in part the far transported and therefore winnowed part of ashes from slightly bimodal eruptions.

Several tephras were interpreted from magnetic analyses on Elephant Island, and these were correlated with other areas, based on C-14-dates, but there were no correlation with help of chemical element analysis (Björck et al. 1991c).

In Sombre Lake (South Orkney Islands, c. 800 km east from Byers Peninsula) seven tephra horizons were observed, whereof four acidic and three basaltic tephras (Hodgson et al. 1998). All these tephras are believed to be from eruptions from Deception Island, even if these eruptions are mainly basaltic and not acidic (Hodgson et al. 1998).

In Bransfield Basin/Strait (see fig. 1), in marine sediments, basaltic to basaltic-andesitic glass shards (brownish to black in colour) plot in the geochemical field of Deception Island, except one ash layer which is younger than a few hundred years. It is speculated that this last ash layer is from the subaqueous Hook Ridge even though we do not know the chemical composition of this ridge (Fretzdorff and Smellie 2002).

3. Material and methods

3.1. Pretreatment of samples

Cores of lake sediments were collected from the geographical center and probably deepest parts of three small lakes, with a Russian peat corer (diam. 5-10 cm) or a Livingston-type corer (diam. 9 cm) by Rolf Zale, the Antarctic summers of 1987-1988 and 1988-1989. The lakes were cored in relatively flat areas, and not too close to main drainage catchment or inlets/outlets/shores. (See more details in Zale 1993.)

Samples were pretreated for grain size etc. and geochemical analyses with the methods described by Rose et al. (1996). These methods for separating shards from the bulk sediment are aggressive, including strong acids, also dissolving small parts of the shards (Rose et al. 1996, Blockley et al. 2005). Therefore the ratios between different major and minor elements in the surface layers of the grains may have been altered; but this can sometimes take place even by rinsing in demineralized water (Blockley et al. 2005). But, as the grains were polished before chemical analysis with WDS and LA-ICP-MS, we suspect that the problems from dissolved parts of the shards in the pretreatment process have been diminished. If grain size is larger than 80 µm, and grain rims are not measured, the result should not have changed because of the laboratory treatment (compare to Jochum et al. 2011). The samples analysed by EDS were not polished before analysis, which may have hampered these results (see Discussion, in this work).

15 3.2. Subsampling for grain size, grain and tephra identification, and chemical analysis

3.2.1. General description of subsampling procedure

Subsamples had been taken with a pipette, one drop of water from a stirred water sample, following standardized methods (pers. comm. Rolf Zale 2011). After drying, the subsamples were glued with Canada balsam to glasses for microscopy, and studied by a polarizing light microscope for grain size and grain concentration analysis of volcanogenic grains. No point counter was available (i.e. Lowe 2011).

Silicic shards are clear or slightly brown under a single polarizer but usually turn black/die off when using two nicols (Sarna-Wojcicki 2000, Enache and Cumming 2006, Lowe 2011), as is also the case with grains of different compositions (see Results, in this work). Because it is more difficult to observe something that disappear, than something which glow up, shards are not easy to quickly distinguish and count under a light microscope. It may also be difficult to positively identify shards only by their physical appearance, as grains smaller than c. 180 µm display fewer identifiable surface microtextures (Molén 1992, and see pictures in e.g. Sarna-Wojcicki 2000) and almost all grains recorded in the current research were smaller than 100 µm (Appendix 1). In the samples in the current research, volcanogenic mineral grains in general were apparently more abundant than shards, and they were much easier detected. Volcanogenic mineral grains usually light up and are easily visible, clear white or slightly gray under double polarizers (i.e. - displaying birefringence), and turn to clear or display small brown colour variations during turning off one polarizer to get single plan polarized light. Therefore, identification of possible tephras were done with volcanogenic mineral grains.

Mineral grains with clear cleavage, rugged edges, and conglomerates of grains are probably from bedrock, e.g. mica and feldspar, and therefore not counted. Opaline/biogenic grains, and contaminating rounded grains with no or single fractures from Paleozoic/Mesozoic sandstones, if found, are easily detected by grain morphology and have been removed (e.g. Molén 1992, Sarna-Wojcicki 2000, Blockley et al. 2005, Lowe 2011). Grain size and concentration analysis of volcanogenic mineral grains were read from 129 samples (Midge Lake: 10 samples, Lake Boeckella: 89 samples, Hidden Lake: 30 samples) and analysed with the help of diagrams and statistics (Appendix 1), on sections of sediment cores which could be possible to correlate. More than 40 000 grains were counted. The samples were encrypted during grain analysis, so that there was no possibility of prejudice in the recording of tephra layers during the hand counting of the grains.

3.2.2. Statistics

The numbers of volcanogenic mineral grains, observed during grain size analysis, are graphed in diagrams (figs. 5-7). The peaks and lows in the graphs are analysed with common standard deviation, to find statistically significant peaks which are interpreted as tephra horizons (Results and Appendix 1).

Methods for chemically correlating different tephra samples with statistical methods were studied, but as there was not enough data or too much variance in the analytical data, such statistics could not be used in the current research (Appendix 6, table A6:1).

16 3.2.3. Subsampling for chemical analysis

Subsamples of grains, in grain size mainly 40-100 µm, were collected with a micropipette under polarized light, for chemical analysis with WDS, LA-ICP-MS and EDS, to find out the chemical composition and if any grains were shards. From the possible tephras, first c. 500 volcanogenic mineral grains from 10 samples were hand picked with the help of a polarizing microscope, to chemically analyse and see how many grains were shards (see details in Appendix 2). For the analysis only between c. 150 and 300 grains (depending on how the samples should be analysed), was necessary, to get a statistically valid result, so a surplus was collected if anything should not work in the analysis. As most grains in the samples were close to 20 ìm, it was difficult to find enough grains. Hence, quite a number of grains were around 40 ìm. Every 20 grains took about 2-4 hours to separate and mount. These were separated on three mounts with 5-8 rows of grains on each mount.

For EDS-analysis another 132 grains from three samples were subsampled (again a surplus). The grains where glued at once to the mount, with no epoxy and polishing. The subsamples were separated with thin plastic bristles (e.g. from a tooth brush), in different patterns, then photographed in overview and then more in detail with visible grains, so that the grains should be easily identified after transfer to another instrument (fig. 4).

3.2.4. Analysis by WDS, EDS and LA-ICP-MS

3.2.4.1. Instruments and calculations

Tephras in the three lakes in the current research have earlier been correlated by different means (Björck et al. 1991a), but not with chemical analyses.

To find the elements which are most profitable to analyse for correlational work, chemical analysis from former studies of tephra and volcanoes in the area has been tabulated and discussed (see Introduction, in this work, and Appendix 5).

Elements were analysed by WDS (JEOL JXA-8200, WDS/EDS combined analyser) at the University of Copenhagen and LA-ICP-MS (ESI/NWR213 and a Thermo Finnegan Element II) at the laboratory of GEUS, following standard methods (Pearce et al. 2007, Jochum et al. 2011, Lowe 2011), and a Cambridge Stereoscan S360 EDS system at the EM-platform at the University of Umeå. The grains where coated with carbon before analysis with WDS and EDS.

The LA-ICP-MS was installed at 40% UV, 5Hz, and a 8 ìm laser beam, 213 nm, for 30 s. At larger beams than 8 ìm, i.e. 13 µm and 20 µm, the grains usually popped. It appears that a beam of 8 ìm is possible to use, with still good accuracy in most cases (Pearce et al. 2011). Laser fluency was 2.80 J/cm2. The beam size in the WDS was 10 ìm, and in the EDS beam size was 200 nm.

The following isotopes were used for analyses with LA-ICP-MS: Mg-24, Al-27, Si-29, Sc-45, Ti-49, V-51, Cr-52, Mn-55, Ni-60, Cu-63, Rb-85, Sr-88, Y-89, Zr- 90, Nb-93, Ba-137, La-139, Ce-140, Pr-141, Nd-146, Sm-147, Eu-153, Gd-157, Tb-159, Dy-163, Ho-165, Er-166, Tm-169, Yb-172, Lu-175, Hf-178, Ta-181, Th-232 and U-238.

17 Fig. 4. Mount for EDS, with plastic bristles in a pattern. Upper picture is ov erv iew of sample LB88. Lower picture is closeup of the lower left area of upper picture. Quite a few grains are v isible, some grains in one line touching the left side of the upper left bristle, two grains a the bottom of the same bristle, and quite a few grains in the open area in the middle of the photograph. A large triangular ty pical shard with a circular imprint of an air bubble, is v isible in the lower part of this open area. (See arrow; i.e. grain MM1 9.)

18 The samples analysed by WDS may be recalculated to 100% weight, because water and other light volatiles will usually disappear from the sample and also can not be analysed by most methods (Sarna-Wojcicki 2000). Some authors dispute that the samples shall be recalculated to normalisation (Lowe 2011). In Europe researchers commonly do not normalise the data, but North Americans do normalise (Pearce et al. 2007). The problem with normalisation is that you do not measure what is in the sample, but only what does not disappear, and even if you will get a better agreement between different samples after normalisation, in the end this may be the wrong result (Hunt and Hill 1993). Another minor problem with EPMA-analysis is that phosphorous and some other light elements, which usually have a lower ratio than 1%, and, hence, do not change the ratios of the other elements very much if these light elements are analysed or not, are measured in some papers, and not in others, but the ratios are still summed up to 100%. In the current work the samples are not normalised. Also, the total percentage measured by WDS may often be more than 100%. Some authors discard these (Kraus et al. 2013, in press), but at least for the EDS data it is a mathematical calculation problem (pers. comm. Per Hörstedt 2012).

During recording of the EDS data, at first a preliminary visual analysis was done of the data on the computer screen of the instrument, to see what elements were present in the grains that were recorded. If a grain showed no similarity to a shard, it was not analysed. Grains with possible similarities to shards were analysed. The analytical data is compared to samples from volcanoes and other places documented by many other researchers, in the Result section, with the help of common scatter diagrams used by many other tephrochronologists.

The EDS data has to be changed from atomic percentage of elements, to oxide weight percentage similar to the WDS data (see Supplementary material, CD). The EDS can not detect the difference between Fe2+ or Fe3+, but in the current work all was converted to FeO

(t). The maximum error in weight percentage of Fe, if all Fe was in the form of Fe2O3, instead of FeO, is less than 10%, and it is less than 1% for each single other oxide. Also, if the four minor elements recorded with EDS, which are not often measured by WDS, i.e. P, S, Cl and Zn, are subtracted, the percentages of the other elements almost do not change because these minor elements have such low abundances. Including all the conversions, these are still minor errors, except for Fe, compared to all other uncertainties. But, a 10% possible difference for Fe is still not that important when comparing different volcanoes, and taking other sources of error into account (e.g. interlaboratory differences).

3.2.4.2. Mounts and transferring of samples

Mounts were glued with epoxy, polished and covered with carbon at GEUS, Copenhagen (see details of mounting procedure in Appendix 2). The last mount, mount 3, had to be polished and covered with carbon three times, as it was glued askew, and grains were inside the epoxy and impossible to measure with WDS. This mount was also filled with air bubbles, and no grains inside air bubbles, and no grain at all from mount 3, could be measured with LA-ICP- MS, and about half of the grains had disappeared in the gluing and polishing process.

Transfer from one instrument to another often is a problem (e.g. Admon et al. 2005, Kuehn and Froese 2010). One reason for this is that the physical appearance of the grains are different in different instruments. During subsampling with a micropipette, in a drop of water, the grains appear slightly different than during grain size analysis when grains are

19 inside of Canada balsam. In a stereo microscope with very high magnification, because the light is from above and not from below, the appearance also is different. In the WDS the grains show up very different from when studied under the optical microscope, but the difference in physical appearance between WDS and LA-ICP-MS is the largest. After moving the mounts to the LA-ICP-MS-instrument, it was very difficult to find the grains again. The appearance was often totally different, and easily visible grains in the WDS often seemed almost like nothing in the LA-ICP-MS. Also, the analysis and recording of the physical positions of grains on the mounts, in the WDS, was done in a much smaller magnification than was possible for the LA-ICP-MS. So, grains which were easily found in the WDS were very difficult to find in the LA-ICP-MS, as the image area on the screen became c. 25 times larger to search, i.e. showing a much smaller area in a much higher magnification.

3.2.5. Step by step analyses of LA-ICP-MS-results

Kraus et al. (2013, in press), conducted the most thorough research in the Antarctic Peninsula area, to find differences in major and trace element compositions, from different volcanoes. All their raw data is published in their supplementary material, which make it easier to compare their research with other published data. From the analysis done by Kraus et al. (2013, in press), the “logistics” tree show how to compare chemical data to find out the source volcano of the tephras in the research area. Two volcanoes may be very similar in some “less important” chemical content, but different in others. Therefore, if the “logistics” tree by Kraus et al. (2013, in press) is used, and source volcanoes is the goal, it is necessary to compare similarities/differences in the correct order. Otherwise wrong volcanoes and tephras may be lumped together, and we can not separate them. The “logistics” tree construction by Kraus et al. (2013, in press) will be followed below, for the nine identified possible volcanic glass shards analysed by LA-ICP-MS in the current research. Following this, the same grains are analysed with the help of scatter diagrams, comparing the same element ratios as in the “logistics” tree.

In the current research the single sample of a lava collected by Kraus et al (2013, in press) from Rezen Peak, is not used in the correlations, because this single sample is not very different from other samples in the area, it is a lava sample, and it is not possible to use for any secure correlations.

Description of “logistics” tree analysis, as shown in table 2. 1. To separate tephras from the Larsen Rift volcanoes, east of the Antarctic Peninsula, from the Bransfield Strait volcanoes, west of the Antarctic Peninsula, Nb/Y is the element ratio which display the highest difference and therefore is best to use. In the Larsen Rift volcanoes Nb/Y is >0.87, and in the Bransfield Strait the same ratio is <0.4. 2. After the first separation, to west or east of the Antarctic Peninsula, the Larsen Rift volcanoes are further separated into a) Paulet Island or b) Cape Purvis and Seal Nunataks, mainly based on Sr and Sr/Y. 3. Cape Purvis and Seal Nunataks are then separated, based on quite a few chemical signatures (see table 2). Seal Nunataks actually are 16 individual volcanoes, and therefore have a large variability in chemical composition, and are not easily separated. 4. To separate Bransfield Strait volcanoes, in the first step, Th/Nb ratios need to be used. This separate Bridgeman Island and Melville Peak from all the other volcanoes. 5. To separate Bridgeman Island and Melville Peak from eachother, Sr/Nb is the most important ratio.

20 6. To separate Inott Point/Rezen Peak/Penguin Island from Deception Island/Sail Rock, Sr/Y is used. (But, e.g., Sr/Y can not be used to separate Deception Island/Sail Rock from Melville Peak/Bridgeman Island volcanoes because they display similar Sr/Y. Hence, if Sr/Y is used first, these volcanoes will not be separated in this “logistics” tree.) 7. Inott Peak is not easily separated from Rezen Peak/Penguin Island but Nb/Y may be used. 8. To separate Rezen Peak from Penguin Island, it is necessary to use many ratios and elements, as the differences are not that large. 9. To separate Deception island from Sail Rock the ratios of Th/Ta, Th/Yb and, in many cases, Ba/Th, are those which display largest differences and therefore are most distinctive.

Table 2. “Logistics” tree, only display ing the main chemical “signals” (simplified after Kraus et al. 201 3, in press). (Numbering as in the text abov e.) ACTION NO.

1 . Separate Bransfield Bransfield: Nb/Y <0.4 Larsen: Nb/Y >0.87 Strait and Larsen Rift

2. Larsen Rift, Paulet Isl., Paulet Isl.: Sr >940 ppm, Sr/Y = Cape Purv is and Seal Nunataks: Sr <7 00 Cape Purv is and Seal 33-39 ppm, Sr/Y <29 Nunataks

3. Cape Purv is and Seal Cape Purv is: Sr = 500-7 00 ppm, Seal Nunataks: Sr = 350-600 ppm, Sr/Y =

Nunataks Sr/Y = 23-29, Th/Yb = 1 .0-1 .3, TiO12 6-26, Th/Yb = 1 .1 -2.2, TiO2 1 .7 -2.7 %, 2.1 -2.8%, Ba/La = 5.5-8.0, Ta = Ba/La = 5.1 -9.6, Ta = 0.9-3.1 ppm, La/Yb 1 .4-2.0 ppm, La/Yb = 9-1 4 = 7 -1 9

4. Separate Bransfield Bridgeman Isl. and Melv ille Peak: Inott Point, Rezen Peak, Penguin Isl., Sail Strait v olcanoes Th/Nb >1 .2 Rock and Deception Isl.: Th/Nb <0.5

5. Bridgeman Isl. and Bridgeman Isl.: Sr/Nb <325 Melv ille Peak: Sr/Nb >380 Melv ille Peak

6. Inott Point, Rezen Peak Inott Point, Rezen Peak and Sail Rock and Deception Isl.: Sr/Y = 21 -26 and Penguin Isl. from Sail Penguin Isl.: Sr/Y = 34-40 or >37 or <25 Rock and Deception Isl.

7 . Separate Inott Point Inott Point: Nb/Y = 0.3-0.4 (or, Rezen Peak and Penguin Isl.: Nb/Y = 0.1 - from Rezen Peak and 0.33-0.38) 0.3 Penguin Isl.

8. Rezen Peak and Rezen Peak: Ba/La >20, Ba/K Penguin Isl.: Ba/La 1 4-1 9, Ba/K 0.03-0.04,

Penguin Isl. >0.04, La/Yb = 5-6, TiO2 <1 %, La/Yb = 7 -1 0, TiO2 >1 %, Zr/Hf = 27 -56 Zr/Hf <25

9. Sail Rock and Sail Rock: Th/Ta >7 .2, Th/Yb >1 .2,Deception Isl.: Th/Ta <5, Th/Yb = 0.2-0.7 , Deception Isl. Ba/Th <50 Ba/Th = 56-1 30

21 4. Results

4.1. Tephra horizon identification

As is seen from Appendix 1 and figs. 5-7, from c. 10% to more than 50% of the number of volcanogenic mineral grains measured in the lake sediments, throughout the cores, are background.

After statistical analysis, the following samples were chosen for chemical analyses because they were considered to be possible tephra horizons (see Appendix 1 for details): * Midge Lake, samples at 0-1, 4-5 and 6-7 cm depth (ML1, ML5, ML7). * Lake Boeckella, samples at 9-10, 17-18, 59-60 and 87-88 cm depth (LB10, LB18, LB60, LB88). * Hidden Lake, samples at 7-8, 16-17 and 28-29 cm depth (HL8, HL17, HL29).

Volcanogenic mineral grains (e.g. quartz and feldspars), will not be used for correlations, but only shards. From the WDS-data, shards have been separated from other grains in the research area, in Appendix 3 (table A3:1-5). All grains analysed by EDS, and which are displayed in figs. 12-19, have a chemical composition similar to shards.

Grain size in Midge Lake was predominantly 20-60 µm, but a few grains were larger than 80 µm. The grain size is almost similar in Lake Boeckella and Hidden Lake (Appendix 1, table A1:7). The grain size in the current research is smaller than previously recorded from Midge Lake by Hodgson et al. (1998), but as they measured shards, and not volcanogenic mineral grains, the grain size results are not easily comparable.

Depth cm

Fig. 5. Numbers of observ ed v olcanogenic mineral grains from Midge Lake. Tephras were interpreted at depths/samples 0-1 cm/ML1 , 4-5 cm/ML5 and 6-7 cm/ML7 . (See Appendix 1 for raw data and calculations of standard dev iation.)

22 Depth (cm)

Fig. 6. Numbers of observ ed v olcanogenic mineral grains from Lake Boeckella. Tephras were interpreted at depths/samples 1 9-20, 59-60 and 87 -88 cm. The top at 20 cm, sample LB20, stretched upwards to sample LB1 0, and samples LB1 0-LB1 9 are interpreted as a lag effect or possible a v olcanic eruption of longer endurance. Sample LB60 is considered a single peak because there is no lag effect, as opposite to the peaks at 20 and 88 cm. The LB1 0 peak may hav e originated because of e.g. a heav y rainfall. The observ ations and counting of v olcanogenic grains in Lake Boeckella conform to similar observ ations by Rolf Zale (unpublished). Number zero at Y-axis is the sample from 0-1 cm, number 5 at Y-axis the sample from 5-6 cm, and so on. (See Appendix 1 for raw data and calculations of standard dev iation.)

23 Depth (cm)

Fig. 7 . Numbers of observ ed v olcanogenic mineral grains from Hidden Lake. Tephras were interpreted at depths/samples 7 -8 cm/HL8, 1 6-1 7 cm/HL1 7 and 28-29 cm/HL29. The observ ations and counting of v olcanogenic grains in Hidden Lake conform to similar observ ations by Rolf Zale (unpublished). (See Appendix 1 for raw data and calculations of standard dev iation.)

4.2. Chemical analysis - WDS followed by LA-ICP-MS, testing a method

Four major elements - Mg, Al, Ti and Si - were analysed both by WDS and LA-ICP-MS, to use the ratios between these elements for comparing the analytical results from the two instruments. However, at the small beam size of 8 µm, combined with the small amount of Mg and Ti, only Al and Si could be measured correctly all the time. The LA-ICP-MS- instrument had problems to record the small atom Mg, so with this instrument there was no reading at all from Mg. The data from comparing Al and Si, display a difference from minus 18% to plus 56% (one sample was plus 121%), between the WDS and LA-ICP-MS, from absolute similarity (Supplementary material on CD).

The nine grains which were measured by LA-ICP-MS, and interpreted as possible shards, from all horizons in the three lakes, are first analysed with the “logistics” tree following the descriptions in table 2 (above). This is done in the text below, using the analytical data from these grains (data in table 3). After that, the same nine grains are analysed with the help of the same scatter diagrams that Kraus et al. (2013, in press) used, i.e. figs. 8-11.

According to action no. 1 (table 2), Nb/Y-ratio, all nine grains are from volcanoes west of the Antarctic Peninsula, except maybe LA-135 (see table 3). Then, according to action no. 2, grain LA-135 is from Cape Purvis or Seal Nunataks (<700 ppm Sr, Sr/Y <29). According to action 3, this grain is probably not from any of these volcanoes, because the Sr is way too

24 low. The conclusion is, then, that this grain is from Bransfield Strait too or from some unknown volcano. But, for LA-135, 12 of 13 element ratios tabulated below are the most, or second most, deviant compared to the eight other grains, and it is therefore possible that this grain is a “foreign” grain.

Action 4, Th/Nb >1.2, separate out grains LA-133, LA-122, LA-110 and LA-131. According to action no. 5, all these grains are from Bridgeman Island c. 100 km north-west of Lake Boeckella, because they have a very low Sr/Nb-ratio. Grains LA-133, LA-122, and LA-110 are all from Lake Boeckella, and LA-131 is from Hidden Lake. Grain LA-133 is only 82.6%, total, and, hence, the data is not significant enough. A value of 95% total weight percent (or in some cases 90%), of all elements added, commonly is the lower limit for researchers to use the data.

The grains LA-36, LA-38 and LA-39 from Midge Lake and LA-97 from Hidden Lake are, after analysis according to action no. 6, all from Sail Rock or Deception Island because of their low Sr/Y-ratio. And, according to action no. 9, probably three of these four grains, those from Midge Lake, are from Deception Island (action no. 7 and 8 are not relevant for these grains). The Ba/Th-ratio is a little bit low for one these grains, but all the other data fits very well with Deception Island.

Table 3. Calculations for the nine possible shards analy sed by LA-ICP-MS, following the comparisons in table 2. The first sample label is the grain sample number with the prefix LA, showing that the grain has been analy sed by LA-ICP-MS. The second label is the lake and horizon the grain is from. Grains LA-1 35 and LA-1 1 0 are interpreted as Fe-mineral grains (marked with bold and italics - see Discussion). The three grains from Midge Lake (ML1 ) are probably from Deception Island (in italics). Grain LA-97 is probably a feldspar (see Discussion, below). The other three grains appear to be from Bridgeman Island, according to the “logistics” tree, but not so if the data is analy sed from fig. 8 - fig. 1 1 . These three grains may also be v olcanogenic minerals, with a somewhat intermediate composition. (See text for details.)

Sample Ti (%) Sr Y Nb/Y Sr/Y Th/Y b Ta/Y b Ba/La Th/Nb Sr/Nb La/Y b Ba/Th Th/Ta LA-36, ML1 1.74 118 20.81 0.262 5.668 0.211 0.161 18.15 0.225 21.6 0.998 86.04 1.309 LA-38, ML1 1.473 220.9 44.56 0.176 4.96 0.367 1.151 13.41 0.18 28.14 3.589 131.1 0.319 LA-39, ML1 1.59 126.6 18.82 0.175 6.724 0.485 0.164 19.44 0.888 38.35 0.75 30.06 2.96 LA-122, LB10 0.033 197.2 17.99 0.136 10.96 3.518 0.323 50.76 16.58 80.8 36.82 531.3 10.91 LA-133, LB10 0.288 60.86 7.58 0.252 8.029 6.015 0.303 11.28 23.15 31.86 0.22 0.419 19.82 LA-135, LB10 2.43 5.94 11.28 0.738 0.527 0 0.616 433.2 0 0.714 0.45 ERR 0 LA-110, LB18 3.9 **** 4629 0.17 0 0.8 0.98 ERR 2.09 0 0 8.45 0.82 LA-97, HL8 0 127.4 7.34 0.256 17.35 0 0.488 263.8 0 67.74 1.333 ERR 0 LA-131, HL29 0.031 170.1 15.21 0.259 11.18 0.964 0.163 1.903 5.003 43.17 17.91 35.36 5.901

The analysis below is based upon the same nine grains in table 3 as the “logistics” tree analysis above. The data is compared to many other samples from the literature, by using the most relevant and similar diagrams as Kraus et al. (2013, in press) does, i.e. figs. 8-11. The conclusions above are partly changed, as seen from the discussion below concerning the diagrams of chemical compositions. Raw data is in table 4, and in figs. 8-11.

A) It is clear that the volcanoes and samples are ordered in different groups, as outlined above. E.g. in fig. 8 almost all samples from volcanoes are in the same area, but still with a clear distinction - Larsen Rift volcanoes mainly in one area a little left and up, and Bransfield Strait volcanoes a little right and both down and up in the diagram. And, it is possible to see differences in element composition between many of the volcanoes, as they are grouped together individually.

25 B) Deception Island, Hurd Peninsula (see fig. 3 for location) and Midge Lake data are always grouped close together, except that two grains from Midge Lake display a lower La/Yb-ratio (fig. 10) and one Midge Lake grain display a higher Th/Nb-ratio (fig. 11). C) The “aberrant” grains LA-110, LA-135 and LA-97, and the three grains LA-122, LA-133 and LA-131 display the most spread of values of all grains. Grains LA-110 and LA-135 are interpreted as Fe-minerals (e.g., see fig. 8). D) According to the “logistics” tree, the three grains LA-122, LA-133 and LA-131, are from Bridgeman Island. However, this was founded upon action 4, that Bridgeman Island and Melville Peak display Th/Nb >1.2, and action 5, that Sr/Nb <325. But, these three grains have much higher Th/Nb values than almost all other grains (fig. 11, all these grains are outside of diagram). They also display much lower Sr/Nb than the Melville Peak and Bridgeman Island samples and are instead more similar to Deception Island (fig. 10). And they also display a Nb/Y higher than Bridgeman Island and Melville Peak - again more similar to Deception island (figs. 9 and 11). Hence, it is more probably that these three grains are from Deception Island or some other volcano.

26 Table 4. Samples used for figs. 8-1 1 , for comparisons of grains in the current research with other sites. All samples with numbers from 84-1 95 in left column are from Kraus et al. (201 3, in press) except the LA-grains which are from the current research. Lower numbers is older data. Numbering of samples as in Appendix 5. Full data in Appendix 5 and in Supplementary material on CD. All samples are from v olcanoes except Hurd Peninsula data and the LA-ICP-MS-data. DI = Deception Island.

27 (Table 4, continued.)

28 (Table 4, continued.)

29 Fig. 8. Comparison of SiO2 (X-axis) and Na 2O+K2O (Y-axis). Grains LA-1 1 0 (from sample LB1 8) and LA-1 35 (from sample LB1 0) are separated from all others, and are interpreted as Fe-minerals. LA-97 (from sample HL8) and LA-1 31 (from sample HL29) are also separated from all others. LA-97 is interpreted as a feldspar, because it is often separated from all others. But LA-1 31 sometimes is grouped with other grains, and therefore is still considered a shard. All grains from ML1 are within or close to the field of Deception Island. The last two grains, from Lake Boeckella, LA-1 22 and LA-1 33 are at two different positions in the diagram.

Legend. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake

Bransfield Rift volcanoes Larsen Rift volcanoes Samples

x = Deception Island + = Cape Purv is = Grains LA-36, LA-38, LA- • = Sail Rock := Paulet Island 39 (all from sample ML1 ) — = Inott Point (Liv ingston Island) i = Grains LA-1 22 (LB1 0), LA-1 33 t O = Seal Nunataks = Penguin Island (LB1 0) Ž = Bridgeman Island A = Grains LA-1 35 (LB1 0) and LA- – = Melv ille Peak (King George 1 1 0 (LB1 8) Island) -- - = Low Head and Melv ille Peak = Grain LA-97 (HL8) (King George Island) l = Grain LA-1 31 (HL29)

Ž = Hurd Peninsula glaciers (Liv ingston Island)

30 Fig. 9. Comparison of Nb/Y (X-axis) and SiO2 (Y-axis). Grains LA-1 1 0 (LB1 8) and LA-1 35 (LB1 0) are separated from all others, and are interpreted as Fe-minerals. LA-97 (HL8) and LA-1 31 (HL29) are also separated, but at this time grouped with three data points from Deception Island and one from Lake Boeckella. LA-97 is interpreted as a feldspar. LA-1 31 is still considered a shard, because it is sometimes grouped with other shards. All grains from ML1 are within the field of Deception Island. The last two grains, from Lake Boeckella, LA-1 22 and LA-1 33 are at two different positions in the diagram, but in this diagram close to Deception Island data points.

Legend. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake

Bransfield Rift volcanoes Larsen Rift volcanoes Samples

x = Deception Island + = Cape Purv is = Grains LA-36, LA-38, LA- • = Sail Rock := Paulet Island 39 (all from sample ML1 ) — = Inott Point (Liv ingston Island) i = Grains LA-1 22 (LB1 0), LA-1 33 t O = Seal Nunataks = Penguin Island (LB1 0) Ž = Bridgeman Island A = Grains LA-1 35 (LB1 0) and LA- – = Melv ille Peak (King George 1 1 0 (LB1 8) Island) -- - = Low Head and Melv ille Peak = Grain LA-97 (HL8) (King George Island) l = Grain LA-1 31 (HL29)

Ž = Hurd Peninsula glaciers (Liv ingston Island)

31 Fig. 1 0. Comparison of La/Yb (X-axis) and Sr/Nb (Y-axis). Grain LA-1 1 0 (LB1 8) display a v alue of (0,0), and is therefore outside the range of this diagram. Grain LA-1 35 (LB1 0) are separated from all others (the sy mbol A is outside of the diagram). Both these grains are interpreted as Fe-minerals. LA-97 (HL8) is partly separated from all others. LA-97 is interpreted as a feldspar. LA-1 31 is still considered a shard and is grouped with the Larsen Rift v olcanoes. One grain from ML1 is within the field of Deception Island, and the other two are not far away . The last two grains, from Lake Boeckella, LA-1 22 and LA-1 33 are at two opposite positions in the diagram, they display a different v alue for La/Yb, but a similar v alue for Sr/Nb.

Legend. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake

Bransfield Rift volcanoes Larsen Rift volcanoes Samples

x = Deception Island + = Cape Purv is = Grains LA-36, LA-38, LA- • = Sail Rock := Paulet Island 39 (all from sample ML1 ) — = Inott Point (Liv ingston Island) i = Grains LA-1 22 (LB1 0), LA-1 33 t O = Seal Nunataks = Penguin Island (LB1 0) Ž = Bridgeman Island A = Grains LA-1 35 (LB1 0) and LA- – = Melv ille Peak (King George 1 1 0 (LB1 8) Island) -- - = Low Head and Melv ille Peak = Grain LA-97 (HL8) (King George Island) l = Grain LA-1 31 (HL29)

Ž = Hurd Peninsula glaciers (Liv ingston Island)

32 Fig. 1 1 . Comparison of Nb/Y (X-axis) and Th/Nb (Y-axis). Grains LA-1 1 0 (LB1 8) and LA-1 35 (LB1 0) are separated from all others, and are interpreted as Fe-minerals (LB-1 35 is zero for Th/Nb and is not v isible in the diagram). LA-97 (HL8) and LA-1 31 (HL29) are also separated from all others. LA-97 is interpreted as a feldspar, and in this diagram the Th/Nb-ratio is zero and the grain is not v isible in the diagram. LA-1 31 has a Th/Nb-ratio higher than 5 and is outside of the diagram range. All grains from ML1 are within or close to the field of Deception Island. The last two grains, from Lake Boeckella, LA-1 22 and LA-1 33 are at different positions and far outside of the diagram, because of an exceptionally high Th/Nb-v alue. All v alues abov e 3 for Th/Nb and all v alues higher than 0.40 for Nb/Y (= Larsen Rift v olcanoes) are omitted from this diagram.

Legend. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake

Bransfield Rift volcanoes Larsen Rift volcanoes Samples

x = Deception Island + = Cape Purv is = Grains LA-36, LA-38, LA- • = Sail Rock := Paulet Island 39 (all from sample ML1 ) — = Inott Point (Liv ingston Island) i = Grains LA-1 22 (LB1 0), LA-1 33 t O = Seal Nunataks = Penguin Island (LB1 0) Ž = Bridgeman Island A = Grains LA-1 35 (LB1 0) and LA- – = Melv ille Peak (King George 1 1 0 (LB1 8) Island) -- - = Low Head and Melv ille Peak = Grain LA-97 (HL8) (King George Island) l = Grain LA-1 31 (HL29)

Ž = Hurd Peninsula glaciers (Liv ingston Island)

33 4.3. Chemical analysis - EDS

Three tephra horizons which may be of the approximate same age, where chosen for EDS- analysis, ML7 from Midge Lake, LB88 from Lake Boeckella and HL29 from Hidden Lake (see data in Appendix 1 and 2).

Of a total of 132 sampled grains which were identified as possible shards (grains showing no birefringence, i.e. they turn black under double polarizers, and display no cleavage), 89 were analysed for chemical composition, because these grains displayed possible element abundances common to shards. But 43 grains were not analysed at all, because they displayed typical mineral composition in the preliminary analyses. Of the 89 analysed grains only 64 are identified as shards. So, in total 68 of 132 “shards” were minerals, more than 50% of all grains. (See table A2:2 for the entire data set.)

The analytical data are presented in detail in table 5, in diagrams in figs. 12-19, in Appendix 5 and in Supplementary material. The diagrams used are those most common used for correlation in published articles concerning tephrochronology, except fig. 19 which has been chosen especially for the current research, as it show a different grouping of grains compared to the other diagrams. The data in the diagrams in figure 12a-19a data is from both volcanoes and tephras in the research area. To easier see the different samples, the data in figs. 12b-19b is more specified than those in figs. 12a-19a, the latter only displaying identified shards from lake sediment and glaciers in the research area.

4.3.1. Midge Lake

From all diagrams, figs. 12-19, it can be seen that Midge Lake grains from the highest horizon, ML1, analysed with WDS, display chemical compositions similar to Deception Island and also to tephras from other sites which are interpreted by different researchers to be from Deception Island. But, in figs. 16b-18b (displaying oxides MgO and/or CaO), the Hurd Peninsula and Midge Lake samples from Hodgson et al. (1998) are a little bit separated from ML7 grains analysed by EDS. The two WDS-samples from ML7 are most often outliers, and it may be questioned if they are shards.

The lowest horizon in Midge Lake, analysed by EDS in the current research, ML7, is mainly bimodal, one group with high silica content, and one basic group with a composition more similar to the element ratios of the eruptives of Deception Island. Hence, Midge Lake grains from horizon ML7 display similarities to tephras from King George Island (Lee et al. 2007). But, the chemical composition of the grains from King George Island and ML7 display many differences, even though both are bimodal. King George Island samples display a lower content of Na2O+K2O (fig. 12b) and K2O (fig. 14b) for the high silica samples than the ML7- grains. From fig. 16b is can be seen that King George Island samples also display a lower content of MgO for the high silica samples, and a higher MgO content for the low silica samples, i.e. opposite to the ML7-grains. Furthermore, King George Island samples display a much lower content of CaO for the high silica samples and a slightly lower CaO-content for the low silica samples, compared to ML7-grains (figs. 17b-18b). Finally, King George Island samples display a higher content of FeO/MgO for the high silica samples than the ML7- grains (fig. 19b). For Na2O compared to K2O, ML7 -grains are still in two groups, but King

George Island samples are more clustered (fig. 15b). But, SiO2 compared to TiO2 (fig. 13b) are quite similar for both King George Island and ML7.

34 Even though there are differences, all the similarities, indicate that it is probable that both King George Island samples and ML7 grains are from the same volcano, i.e. Deception Island, and from bimodal eruptions. The MgO-content of ML7-grains analysed by EDS also display a bimodal distribution (fig. 18).

4.3.2. Lake Boeckella

The chemical composition of the grains from Lake Boeckella has a variation of element ratios which often is spread more than the variation of all the other the volcanoes and tephras in the area. The only exception to this is a group of four of five shards analysed by WDS, displaying a high sodium content. The fifth grain analysed by WDS has a total of only 82.6% (grain LA-133), but is similar to a shard in composition.

The large chemical variation in Lake Boeckella grains analysed by EDS, compared to all other samples, is seen when comparing diagrams in figs. 12a-15a and fig. 17a (volcanoes included) to diagrams in figs. 12b-15b and fig. 17b (more detailed diagrams; volcanoes, West Antarctica/MBL samples, and single samples from glaciers, excluded). From fig. 16b and figs. 18b-19b (all with MgO) it is seen that the variation in the chemical composition of the Lake Boeckella grains is smaller than in other diagrams. In 16b it is less than the variation for Hidden Lake and much within the variation for Deception Island, and many grains are close to the silica rich ML7-grains. In fig. 19b the chemical composition of the LB-grains are almost within the chemical variation of Deception Island, and the clustering of the grains almost appear to be in two groups and to be bimodal. Also, in fig. 17 (a-b), it is seen that LB- grains are sorted in low and high CaO-content (this is also evident in fig. 18a-18b).

4.3.3. Hidden Lake

Hidden Lake shard compositions are distributed almost similar to the shards from Lake Boeckella, but commonly with less variation than both Lake Boeckella and West Antarctica/MBL grains (figs. 12-15 and 17-18). But, there are also some similarities between Hidden Lake and Midge Lake, as some shards from Hidden Lake are grouped close to the silicic group of the Midge Lake ML7 shards (figs. 12-19, see especially figs. 14a-b). In fig. 16b and fig. 19b the variation of the chemical composition of Hidden Lake grains actually is larger than for both grains from Lake Boeckella and West Antarctica/MBL.

35 Table 5. Samples used for figs. 1 2-1 9, for comparisons of grains in the current research with other sites. All samples with numbers from 84-1 95, in left column, are from Kraus et al. (201 3, in press) except the LA-grains and grains which are labeled ML, LB or HL in the second column - all the latter are from the current research. Grains analy sed by WDS in the current research are marked. Alla grains labeled MM are the current research EDS data. Lower numbers than 84 that has no labels like ML, LB or HL is older data, from Appendix 5. Samples which are not from the current research are in Appendix 5, and are numbered as in this table. Full data is in Appendix 5 and in Supplementary material on CD. DI = Deception Island.

36 (Table 5, continued.)

37 (Table 5, continued.)

38 (Table 5, continued.)

39 Fig. 1 2a. Comparison of SiO2 and Na 2O+K2O. Data from v olcanoes and tephras in the research area. It is seen that ML-grains are mainly bimodal, one more silicic group and one close to Deception Island, except for a few outliers. Lake Boeckella and Hidden Lake grain ratios are spread more than the v ariation for all v olcanoes and tephras.

Legend for figures 12a-19a, volcanoes and tephras. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Bransfield Rift volcanoes Larsen Rift volcanoes Samples from lakes and glaciers

x = Deception Island + = Cape Purv is = All ML grains • = Sail Rock : = Paulet Island i = All LB grains — = Inott Point (Liv ingston O = Seal Nunataks Island) l = All HL grains t = Penguin Island Ž = Hurd Peninsula glaciers, Liv ingston Isl. Ž = Bridgeman Island — = West Antarctica/MBL – = Melv ille Peak (King : George Island) = EPICA Dome, “from Deception Island” — = “1 641 " eruption, “from Deception Island” A = King George Island

40 Fig. 1 2b. Comparison of SiO2 and Na 2O+K2O. Identified shards from tephras only , samples from lake sediment and glaciers in the research area. From the diagram it can be seen that the chemistry of the ML1 -grains sort within the chemical v ariation of Deception Island (compare to fig. 1 2a). The two WDS-samples from ML7 are outliers. The EDS-data for ML7 is mainly sorted in two groups, one with c. 1 5 grains with high silica content, and one basaltic with c. 1 5 grains with a composition more similar to the element ratios of the eruptiv es of Deception Island. Hence, the sample is bimodal. King George Island samples are also bimodal, but they display a lower content of

Na 2O+K2O for the high silica samples than the ML7 -grains. Four of the fiv e LB-grains analy sed with WDS are sorted in one group, and the grains analy sed by EDS are spread out almost ev enly . The chemical composition of LB- and HL-grains are almost more spread than all the other samples together, including the v olcanoes in fig. 1 2a. The small group of LB-grains analy sed with WDS may be feldspars, as they are almost alway s separated in a group by their own and display a v ery high Na-content. A few HL-grains are sorted together with the silicic ML7 -grains.

Legend for figures 12b-19b. Tephras in lakes and glaciers. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Midge Lake Lake Boeckella Hidden Lake Other lakes and glaciers

= HL-29-WDS A = King George Island = ML1 -WDS j = LB1 0-WDS = ML (Hodgson et al. l = HL-29-EDS • = Hurd Peninsula glaciers, i = LB88-WDS 1 998) Liv ingston Island i = LB88-EDS Ž = Hurd P. glaciers - pre-1 829 = ML7 -WDS O = Hurd Peninsula glaciers, = ML7 -EDS old Deception Island

41 Fig. 1 3a. Comparison of SiO2 and TiO2/K2O. Data from v olcanoes and tephras in the research area. For all diagrams, it is seen that ML-grains are mainly bimodal, one more silicic group and one close to Deception Island, except for a few outliers. Lake Boeckella grain ratios are usually spread more than the v ariation of all v olcanoes and tephras. Hidden Lake data is spread about as much as MBL/West Antarctica v olcanoes.

Legend for figures 12a-19a, volcanoes and tephras. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Bransfield Rift volcanoes Larsen Rift volcanoes Samples from lakes and glaciers

x = Deception Island + = Cape Purv is = All ML grains • = Sail Rock : = Paulet Island i = All LB grains — = Inott Point (Liv ingston O = Seal Nunataks Island) l = All HL grains t = Penguin Island Ž = Hurd Peninsula glaciers, Liv ingston Isl. Ž = Bridgeman Island — = West Antarctica/MBL – = Melv ille Peak (King : George Island) = EPICA Dome, “from Deception Island” — = “1 641 " eruption, “from Deception Island” A = King George Island

42 Fig. 1 3b. Comparison of SiO2 and TiO2/K2O. Identified shards from tephras only , from lake sediment and glaciers in the research area. From the diagram it can be seen that the chemistry of the recent ML1 -grains sort within the chemical v ariation of Deception Island. One of the two WDS-samples from ML7 is an outlier, the other is at 60%

SiO2 and close to zero for TiO2/K2O. The EDS-data for ML7 is mainly sorted in two groups, one with grains with high silica content, and one basaltic with grains with a composition more similar to the element ratios of the eruptiv es of Deception Island. Hence, the sample is bimodal. But, in this diagram it is seen that the TiO2/K2O-ratio for the EDS-analy sed ML7 -grains v aries a lot. Four of fiv e of the LB-grains analy sed with WDS are sorted in one group (the fifth grain has a low total), and the grains analy sed with EDS are spread out almost ev enly . The chemical composition of LB-grains are almost more spread than all the other samples together. The small group of LB-grains analy sed with WDS may be feldspars, as they are almost alway s separated in a group by their own and display a v ery high Na-content. HL-grains are spread out ov er most of the diagrams, except that a few grains are sorted together with or close to the silicic ML7 -grains.

Legend for figures 12b-19b. Tephras in lakes and glaciers. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Midge Lake Lake Boeckella Hidden Lake Other lakes and glaciers

= HL-29-WDS A = King George Island = ML1 -WDS j = LB1 0-WDS = ML (Hodgson et al. l = HL-29-EDS • = Hurd Peninsula glaciers, i = LB88-WDS 1 998) Liv ingston Island i = LB88-EDS Ž = Hurd P. glaciers - pre-1 829 = ML7 -WDS O = Hurd Peninsula glaciers, = ML7 -EDS old Deception Island

43 Fig. 1 4a. Comparison of SiO2 and K2O. Data from v olcanoes and tephras in the research area. For all diagrams, it is seen that ML-grains are mainly bimodal, one more silicic group and one close to Deception Island, except for a few outliers. Lake Boeckella and Hidden Lake grain ratios are usually spread more than the v ariation for all v olcanoes and tephras.

Legend for figures 12a-19a, volcanoes and tephras. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Bransfield Rift volcanoes Larsen Rift volcanoes Samples from lakes and glaciers

x = Deception Island + = Cape Purv is = All ML grains • = Sail Rock : = Paulet Island i = All LB grains — = Inott Point (Liv ingston O = Seal Nunataks Island) l = All HL grains t = Penguin Island Ž = Hurd Peninsula glaciers, Liv ingston Isl. Ž = Bridgeman Island — = West Antarctica/MBL – = Melv ille Peak (King : George Island) = EPICA Dome, “from Deception Island” — = “1 641 " eruption, “from Deception Island” A = King George Island

44 Fig. 1 4b. Comparison of SiO2 and K2O. Identified shards from tephras only , from lake sediment and glaciers in the research area. From the diagram it can be seen that the chemistry of the recent ML1 -grains sort within the chemical v ariation of Deception Island. The two WDS-samples from ML7 are outliers. The EDS-data for ML7 is mainly sorted in two groups, one with c. 1 5 grains with high silica content, and one basaltic with c. 1 5 grains with a composition more similar to the element ratios of the eruptiv es of Deception Island. Hence, the sample is bimodal.

King George Island samples are also bimodal, but they display a lower content of K2O for the high silica samples than the ML7 -grains. Four of fiv e LB-grains analy sed with WDS are sorted in one group, and the grains analy sed by EDS are spread out almost ev enly . The chemical composition of LB- and HL-grains are almost more spread than all the other v olcanoes together. The small group of LB-grains analy sed with WDS may be feldspars, as they are almost alway s separated in a group by their own and display a v ery high Na-content. A few HL-grains are sorted together with or close to the silicic ML7 -grains.

Legend for figures 12b-19b. Tephras in lakes and glaciers. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Midge Lake Lake Boeckella Hidden Lake Other lakes and glaciers

= HL-29-WDS A = King George Island = ML1 -WDS j = LB1 0-WDS = ML (Hodgson et al. l = HL-29-EDS • = Hurd Peninsula glaciers, i = LB88-WDS 1 998) Liv ingston Island i = LB88-EDS Ž = Hurd P. glaciers - pre-1 829 = ML7 -WDS O = Hurd Peninsula glaciers,

= ML7 -EDS old Deception Island

45 Fig. 1 5a. Comparison of Na 2O and K2O. Data from v olcanoes and tephras in the research area. For all diagrams, it is seen that ML-grains are mainly bimodal, one more silicic group and one close to Deception Island, except for a few outliers. Lake Boeckella and Hidden Lake grain ratios are usually spread more than the v ariation for all v olcanoes and tephras.

Legend for figures 12a-19a, volcanoes and tephras. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Bransfield Rift volcanoes Larsen Rift volcanoes Samples from lakes and glaciers

x = Deception Island + = Cape Purv is = All ML grains • = Sail Rock : = Paulet Island i = All LB grains — = Inott Point (Liv ingston O = Seal Nunataks Island) l = All HL grains t = Penguin Island Ž = Hurd Peninsula glaciers, Liv ingston Isl. Ž = Bridgeman Island — = West Antarctica/MBL – = Melv ille Peak (King : George Island) = EPICA Dome, “from Deception Island” — = “1 641 " eruption, “from Deception Island” A = King George Island

46 Fig. 1 5b. Comparison of Na 2O and K2O. Identified shards from tephras only , from lake sediment and glaciers in the research area. From the diagram it can be seen that the chemistry of the recent ML1 -grains sort within the chemical v ariation of Deception Island. The two WDS-samples from ML7 are outliers. The EDS grains from ML7 are sorted in two groups, and the sample is bimodal. King George Island grain are not bimodal in this diagram, but all grains are quite similar in chemical composition. LB-grains analy sed with WDS are sorted in one group (four of fiv e grains), and the grains analy sed by EDS are spread out almost ev enly . The chemical compositions of LB- and HL-grains are almost more spread than all the other samples together. The small group of LB-grains analy sed with WDS may be feldspars, as they are almost alway s separated in a group by their own and display a v ery high Na- content. Some HL-grains are sorted together with or close to the silicic ML7 -grains.

Legend for figures 12b-19b. Tephras in lakes and glaciers. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Midge Lake Lake Boeckella Hidden Lake Other lakes and glaciers

= HL-29-WDS A = King George Island = ML1 -WDS j = LB1 0-WDS = ML (Hodgson et al. l = HL-29-EDS • = Hurd Peninsula glaciers, i = LB88-WDS 1 998) Liv ingston Island i = LB88-EDS Ž = Hurd P. glaciers - pre-1 829 = ML7 -WDS O = Hurd Peninsula glaciers, = ML7 -EDS old Deception Island

47 Fig. 1 6a. Comparison of SiO2 and MgO. Data from v olcanoes and tephras in the research area. For all diagrams, it is seen that ML-grains are mainly bimodal, one more silicic group and one close to Deception Island, except for a few outliers. Lake Boeckella grain ratios are clustered more close to Deception Island and ML7 -grains than in diagrams 1 2-1 5 and 1 7 . Hidden Lake data is more spread than LB-grains and comparable to MBL/West Antarctica v olcanoes/samples.

Legend for figures 12a-19a, volcanoes and tephras. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Bransfield Rift volcanoes Larsen Rift volcanoes Samples from lakes and glaciers

x = Deception Island + = Cape Purv is = All ML grains • = Sail Rock : = Paulet Island i = All LB grains — = Inott Point (Liv ingston O = Seal Nunataks Island) l = All HL grains t = Penguin Island Ž = Hurd Peninsula glaciers, Liv ingston Isl. Ž = Bridgeman Island — = West Antarctica/MBL – = Melv ille Peak (King : George Island) = EPICA Dome, “from Deception Island” — = “1 641 " eruption, “from Deception Island” A = King George Island

48 Fig. 1 6b. Comparison of SiO2 and MgO. (Notice that the scale of Y-axis has been changed a little, to spread out the data points, compared to fig. 1 6a.) Identified shards from tephras only , from lake sediment and glaciers in the research area. From the diagram it can be seen that the chemistry of the recent ML1 -grains sort within the chemical v ariation of Deception Island. The two WDS-samples from ML7 are outliers. The EDS-data for ML7 is mainly sorted in two groups, one with c. 1 5 grains with high silica content, and one basaltic with grains with a composition more similar to the element ratios of the eruptiv es of Deception Island. Hence, the sample is bimodal. King George Island samples are also bimodal, but they display a lower content of MgO for the high silica samples and a higher MgO content for the low silica samples, i.e. opposite to the ML7 -grains. Four of the fiv e LB-grains analy sed with WDS are sorted in one group, in this diagram close to the acidic/silicic ML7 -grains. The LB-grains analy sed by EDS are more clustered together than in diagrams 1 2-1 5 and 1 7 , with many grains inside the chemical composition of Deception Island or close to the silicic group of ML7 -grains. HL-grains are spread out ov er most of the diagram, except that a few grains are sorted together with the silicic ML7 -grains.

Legend for figures 12b-19b. Tephras in lakes and glaciers. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Midge Lake Lake Boeckella Hidden Lake Other lakes and glaciers

= HL-29-WDS A = King George Island = ML1 -WDS j = LB1 0-WDS = ML (Hodgson et al. l = HL-29-EDS • = Hurd Peninsula glaciers, i = LB88-WDS 1 998) Liv ingston Island i = LB88-EDS Ž = Hurd P. glaciers - pre-1 829 = ML7 -WDS O = Hurd Peninsula glaciers,

= ML7 -EDS old Deception Island

49 Fig. 1 7 a. Comparison of SiO2 and CaO. Data from v olcanoes and tephras in the research area. For all diagrams, it is seen that ML-grains are mainly bimodal, one more silicic group and one close to Deception Island, except for a few outliers. In this diagram the MBL/West Antarctica samples are more spread than the LB-grains. Hidden Lake data is about as spread as the MBL/West Antarctica samples.

Legend for figures 12a-19a, volcanoes and tephras. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Bransfield Rift volcanoes Larsen Rift volcanoes Samples from lakes and glaciers

x = Deception Island + = Cape Purv is = All ML grains • = Sail Rock : = Paulet Island i = All LB grains — = Inott Point (Liv ingston O = Seal Nunataks Island) l = All HL grains t = Penguin Island Ž = Hurd Peninsula glaciers, Liv ingston Isl. Ž = Bridgeman Island — = West Antarctica/MBL – = Melv ille Peak (King : George Island) = EPICA Dome, “from Deception Island” — = “1 641 " eruption, “from Deception Island” A = King George Island

50 Fig. 1 7 b. Comparison of SiO2 and CaO. Identified shards from tephras only , from lake sediment and glaciers in the research area. From the diagram it can be seen that the chemistry of the recent ML1 -grains sort within the chemical v ariation of Deception Island. The two WDS-samples from ML7 are outliers. The EDS-data for ML7 is mainly sorted in two groups, one with c. 1 5 grains with high silica content, and one basaltic with many grains display ing a composition more similar to the element ratios of the eruptiv es of Deception Island. Hence, the sample is bimodal. King George Island samples are also bimodal, but they display a much lower content of CaO for the high silica samples and a slightly lower CaO-content for the low silica samples, than the ML7 -grains. Four of the fiv e LB-grains analy sed with WDS are sorted in one group, and the grains analy sed by EDS are spread out more ev enly but in this case one group with high a CaO-content and one group display ing a low CaO-content. HL- grains are spread mostly ov er the lower part of the diagram and some are together with the high silica group of ML7 .

Legend for figures 12b-19b. Tephras in lakes and glaciers. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Midge Lake Lake Boeckella Hidden Lake Other lakes and glaciers

= HL-29-WDS A = King George Island = ML1 -WDS j = LB1 0-WDS = ML (Hodgson et al. l = HL-29-EDS • = Hurd Peninsula glaciers, i = LB88-WDS 1 998) Liv ingston Island i = LB88-EDS Ž = Hurd P. glaciers - pre-1 829 = ML7 -WDS O = Hurd Peninsula glaciers,

= ML7 -EDS old Deception Island

51 Fig. 1 8a. Comparison of MgO and CaO. Data from v olcanoes and tephras in the research area. The ML-grains are in one v ery tight group with higher content of MgO and one group more spread out with mostly a lower content of MgO. Lake Boeckella grain ratios are almost sorted in two groups, with high and low concentration of CaO. In this diagram it is easily seen that the Larsen Rift v olcanoes and many of the Bransfield Strait v olcanoes hav e a higher MgO-content than other v olcanoes and samples, e.g. higher MgO than Deception Island.

Legend for figures 12a-19a, volcanoes and tephras. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Bransfield Rift volcanoes Larsen Rift volcanoes Samples from lakes and glaciers

x = Deception Island + = Cape Purv is = All ML grains • = Sail Rock : = Paulet Island i = All LB grains — = Inott Point (Liv ingston O = Seal Nunataks Island) l = All HL grains t = Penguin Island Ž = Hurd Peninsula glaciers, Liv ingston Isl. Ž = Bridgeman Island — = West Antarctica/MBL – = Melv ille Peak (King : George Island) = EPICA Dome, “from Deception Island” — = “1 641 " eruption, “from Deception Island” A = King George Island

52 Fig. 1 8b. Comparison of MgO and CaO. Identified shards from tephras only , from lake sediment and glaciers in the research area. From the diagram it can be seen that the chemistry of the recent ML1 -grains sort within the chemical v ariation of Deception Island. The two WDS-samples from ML7 are outliers. The EDS-data for ML7 is mainly sorted in two groups, one with higher MgO-content and one with lower MgO-content. Neither of these two groups hav e a composition similar to the element ratios of the eruptiv es of Deception Island. And, the sample may also be described bimodal for this element composition. Again the King George Island samples are bimodal, but they display a CaO content which is clearly lower than the ML7 -grains. Four of the fiv e LB-grains analy sed with WDS are sorted in one group, and the grains analy sed with EDS are sorted closer to the Deception Island chemical compositions than in diagrams 1 2-1 5 and 1 7 . The small group of LB-grains analy sed with WDS may be feldspars, as they are almost alway s separated in a group by their own and display a v ery high Na-content. HL-grains are not as much spread as in most other diagrams. Both grains from LB and HL are closer to Deception Island compositional data in this diagram than for other element comparisons.

Legend for figures 12b-19b. Tephras in lakes and glaciers. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Midge Lake Lake Boeckella Hidden Lake Other lakes and glaciers

= HL-29-WDS A = King George Island = ML1 -WDS j = LB1 0-WDS = ML (Hodgson et al. l = HL-29-EDS • = Hurd Peninsula glaciers, i = LB88-WDS 1 998) Liv ingston Island i = LB88-EDS Ž = Hurd P. glaciers - pre-1 829 = ML7 -WDS O = Hurd Peninsula glaciers, = ML7 -EDS old Deception Island

53 Fig. 1 9a. Comparison of SiO2 and FeO/MgO. Data from v olcanoes and tephras in the research area. For all diagrams, it is seen that ML-grains are mainly bimodal, one more silicic group and one close to Deception Island, except for a few outliers. Lake Boeckella grains are almost within the chemical composition of Deception Island, and Hidden Lake grains are also more clustered.

Legend for figures 12a-19a, volcanoes and tephras. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Bransfield Rift volcanoes Larsen Rift volcanoes Samples from lakes and glaciers

x = Deception Island + = Cape Purv is = All ML grains • = Sail Rock : = Paulet Island i = All LB grains — = Inott Point (Liv ingston O = Seal Nunataks Island) l = All HL grains t = Penguin Island Ž = Hurd Peninsula glaciers, Liv ingston Isl. Ž = Bridgeman Island — = West Antarctica/MBL – = Melv ille Peak (King : George Island) = EPICA Dome, “from Deception Island” — = “1 641 " eruption, “from Deception Island” A = King George Island

54 Fig. 1 9b. Comparison of SiO2 and FeO/MgO. Identified shards from tephras only , from lake sediment and glaciers in the research area. From the diagram it can be seen that the chemistry of the recent ML1 -grains sort within the chemical v ariation of Deception Island. The two WDS-samples from ML7 are outliers (one grain is outside of the range of the diagram). The EDS-data for ML7 is mainly sorted in two groups, one with c. 1 5 grains with high silica content, and one basaltic with c. 1 5 grains with a composition more similar to the element ratios of the eruptiv es of Deception Island. Hence, the sample is bimodal. King George Island samples are also bimodal, but they display a higher content of FeO/MgO for the high silica samples than the ML7 -grains. Four of the fiv e LB-grains analy sed with WDS are sorted in one group. The small group of LB-grains analy sed with WDS may be feldspars, as they are almost alway s separated in a group by their own and display a v ery high Na-content. HL-grains are spread out mostly in the lower part of the diagram, and a few grains are sorted together with or close to the silicic ML7 -grains. Grains from HL but especially from LB are closer to Deception Island compositional data than for other element comparisons (compare to fig. 1 9a). Grains from LB are almost all inside of Deception Island, while grains from Hidden Lake in this case display larger differences in their chemical composition.

Legend for figures 12b-19b. Tephras in lakes and glaciers. ML = Midge Lake, LB = Lake Boeckella, HL = Hidden Lake.

Midge Lake Lake Boeckella Hidden Lake Other lakes and glaciers

= HL-29-WDS A = King George Island = ML1 -WDS j = LB1 0-WDS = ML (Hodgson et al. l = HL-29-EDS • = Hurd Peninsula glaciers, i = LB88-WDS 1 998) Liv ingston Island i = LB88-EDS Ž = Hurd P. glaciers - pre-1 829 = ML7 -WDS O = Hurd Peninsula glaciers, = ML7 -EDS old Deception Island

55 5. Discussion

5.1. Measuring grain size and concentration of volcanogenic grains

The methods for subsampling and for hand counting volcanogenic grains for grain size analysis and grain concentration measurements, in order to identify volcanogenic grains and tephra horizons, involve many uncertainties.

The standardized method of hand sampling a drop of subsample from a stirred water suspension, may skew the size of the grains, but probably not the proportion of volcanogenic grains, if the drop of water is taken a) from a different depth in the test-tube, b) not exactly at the same time after stirring, and c) if the stirring is different between different samples. The subsamples also are very small, c. 0.1 gram of a water suspension subsampled from c. 20 g of a water suspension which contain c. 0.1-0.2 g of dry sample. All the shortcomings during the weighting of the samples and of the subsamples alone may skew the number of grains c. 10%.

Another more serious problem in analysis of volcanogenic mineral grains is that all researchers observe different numbers of grains in the samples, sometimes varying as much as an order of magnitude (pers. comm. Rolf Zale 2012). Also, some researchers observe more grains than others when there are few grains in the samples, and some observe more grains when there are many grains in the samples. All this may be because most grains are small, close to 20 µm, and may not be counted by all researchers. And if there are fewer grains in the samples it may sometimes be psychologically easier to mark grains as “volcanogenic”, and if there are many grains it takes too much time to analyse each grain in detail and some “extra” grains may be included in the counting process (e.g. analysing 40 000 grains for 10 s each, will round up to more than 100 hours on top of the time for counting and measuring the grains). Hence, operator variation is the most critical moment of uncertainty in analysis of volcanogenic mineral grains. Nonetheless, even if researchers observe different numbers of grains, the trend of high and low readings (tephras or not) are still similar. Therefore, a tephra usually is always observed, even if the grain counts give different numbers.

However, as has been done in the current work, an important source of possible psychological prejudice was eliminated from the beginning as all samples were encrypted and mixed before grain analysis was started, with no knowledge of what lake or depth the sample came from or where tephra horizons had been observed. This action show if the operator has much fantasy or if volcanogenic grains are actually observed, in comparison with other operators, i.e. in this case in comparison with readings made by Rolf Zale and others (unpublished). If the difference between a significant and an insignificant result for identification of a tephra horizon, in some cases may depend on observation of two single grains (see table A1:4, Appendix 1), any bias may screw the result in a wanted direction.

A minor sampling problem is that shards may be moved by core smearing (Davies et al. 2007). That may perhaps include rare contaminating grains in a sample which is chemically analysed, but if samples are collected inside of the core this will be a minor or non-existent problem. Grain size analysis or grain concentration measurements will not be changed, except if the smearing is more similar to stirring.

56 5.2. Identification of volcanogenic grains and tephra horizons

5.2.1. Cryptotephras, statistics and background populations

Most of the ash layers in the current research will classify as cryptotephras, with a grain size mainly <100-125 µm (Lowe 2011), especially in Lake Boeckella (Zale and Karlén 1989) and Hidden Lake (pers. comm. Rolf Zale 2011), because these tephras are often not visible by the naked eye.

Statistics for identifying tephra horizons are seldom performed or reported. Kylander et al. (2011) used MSE (mean standard error) to try to find tephra horizons but provided no analytical data from the calculations. There was a small background population of volcanogenic grains in at least some samples (only parts of the cores analysed). First those parts of the cores which were supposed to contain tephras were analysed with XRF at 5 cm intervals, then those intervals that contained readings which showed possible tephras were analysed at 1 cm intervals. Finally tephras were identified by readings of higher densities in the core, MSE, spectra scattering and major element abundance. But, the MSE conducted on XRF-data often showed tephra horizons at different depths than was found by hand counting. And, the chemical analyses were not comparable, I would say that they were almost contradictory, between XRF and WDS readings. Otherwise, statistics is mostly used to correlate different tephra horizons (Lowe 2011).

There are difficulties to identify tephra horizons in the lakes in the current research, as there is a large background population of volcanogenic grains in all three lakes, often 10-50% of all grains all through the sampled cores. These background populations are easily explained as lag effects which are common in the arctic climate area (e.g., compare to Davies et al. 2007). Many “background populations”, close to large tephra peaks, are actually higher than other tephra peaks in the same lake, similar to the tephra distribution in a small lake in Sweden with permanent snow cover close by (Davies et al. 2007). In the Swedish lake, very little tephra was deposited at the time of a volcanic eruption recorded in 1875. But, during climatic warming in the 1930:s the permanent snow cover in the area melted and the abundance of tephra from that point and up until at least 2002 (the last date of sampling) became between c. 10-40 times higher than during the year of eruption. The tephra peak with the longest large lag effect, in the current research, is in Lake Boeckella, samples LB10-LB20.

Background populations of tephras in a marine setting in the research area, varies between 10% and 40%, and “at least 13 tephras” were identified that was stated to contain between 60-100% glass shards (Fretzdorff and Smellie 2002). Hence, there was also a much higher ratio of volcanogenic grains in this marine setting than in the small lakes in the current research, as most of the sediments in the tephra layers, in the small lakes, are not volcanogenic but grains from the local bedrock.

In the current research, tephras were interpreted where volcanic mineral grain abundance were more than two standard deviations (95%) from the mean in Lake Boeckella. In Hidden Lake tephras were interpreted first for the uppermost part, and after that for the complete sample series (95%) (see details of calculations in Appendix 1).

Because of the low sediment deposition rate in Midge Lake there were so few samples in the sediment core in the age spectrum analysed, that there was no possibility to arrive at any

57 statistical confident result to determine what horizons were tephras, when calculating with two standard deviations, and therefore only one standard deviation (68%) is used. It is important to analyse Midge Lake more thoroughfully, even if the analysis of variance is within 68%, because other researchers have interpreted many tephras in this thin sequence. With few samples the statistics is not very rigorous. But, because of the low sedimentation rate, any tephra will show up easier in Midge Lake, as ashes will not be much diluted with local bedrock grains, even though the statistics used to verify a tephra horizon arrive at more significant results for Lake Boeckella and Hidden Lake. At the same time, Midge Lake is not in the main wind direction from the volcano which has had most recent eruptions, i.e. Deception Island, and we would not suspect to find much ashes in the lake.

Because of the large background population resident in the three lakes in the current research, any possible tephras from smaller eruptions are hidden from detection in the background noise. And, it is probably that grains from many eruptions during a long time period have been mixed. To find evidence of a special eruption in the background population, a large number of grains have to be chemically analysed.

5.2.2. Volcanogenic mineral grains

Most researchers have not documented or have missed the importance of the presence of volcanogenic mineral grains in ashfalls, but some use minerals (Nakagawa and Ohba 2002, Ohba and Nakagawa 2002, Lowe 2011).

As the identification of tephra horizons in the current research is based on hand counting of volcanogenic mineral grains, it is important to verify that the grains are not local, e.g. from the bedrock. The grains measured during counting of volcanogenic mineral grains in sediments commonly showed no cleavage, which may be an indication that they are not crushed, from bedrock, but volcanic in origin. Only conchoidal fractures were sometimes observed. Quartz grains could have been broken and become shocked during eruptions (a few grains in most samples appeared to be shocked quartz), and quartz also is chemically precipitated from hydrothermal solutions (Ohba and Nakagawa 2002).

If our recorded mineral grains would not have been volcanic in origin, we would suspect that there should also be an abundance of similar white/light grey anisotropic mineral grains, as those here observed, further away from the volcanoes where there is no or little evidence of tephras, in the research area. But, this is not the case (pers. comm. Rolf Zale 2012), which strengthens the view that most of these recorded mineral grains are volcanic in origin. If the mineral grains had been local, we also would suspect that their abundance would not vary very much throughout the sedimentary deposits, and not be absent from horizons where there are few or no indications of tephras. An extraneous source like an ash fall appear to be the only explanation for these mineral grains. A similar systematic variation, with low and high readings of volcanic mineral grains in the samples analysed, was evident in both work by Rolf Zale (unpublished) and in the current research.

Also, as observed in the polarizing microscope, succeeded by WDS, between 10-20% of clearly identified non-quartz “mineral grains” (light white with two polarizers) later turned out to be possible shards (only counting those grains where analysis show >60% total weight percent were measured, excluding some grains e.g. LA-97, HL8; see Appendix 3). If all quartz grains are included, shard abundance is closer to 10%. Grains LA-122 and LA-131 and some

58 other grains (see figs. 12b-19b) which may be classified as shards, have a sodium content of 13-15%, which indicate that they are similar to volcanogenic mineral grains, even though their compositions for other elements are similar to shards. (Most researchers would probably state that these grains are feldspars.) Hence, in the area of tephrochronology, some shards are overlooked because they may be believed to be local mineral grains.

And of all grains analysed by EDS analysis, c. 50% of clearly identified “volcanic silicic shards” (black under double polarizer) turned out to be mineral grains when analysed for elements, e.g. they were pure quartz, zink-rich minerals, feldspars and carbonates. A similar observation was reported by Hodgson et al. (1998), where 95% of suspected shards from an Antarctic Lake (Sombre Lake) were minerals like quartz, hornblende, orthoclase and garnet.

If grains have been misinterpreted in the polarizing microscope, it is not of great importance if they are chemically analysed afterwards. If volcanogenic mineral grains have been included in bulk sediments, the chemical analysis will show wrong element abundances compared to shards. If volcanogenic minerals are analysed separately, sometimes they may be used for correlations (Nakagawa and Ohba 2002, Ohba and Nakagawa 2002, Lowe 2011). If a researcher have missed to document shards with the appearance of minerals, which is actually what is probably almost always done, there are still not so many grains missed, and that will probably not change the results very much. Mineral grains misidentified as shards are detected by chemical analysis, as has been done in the current research, and will be no problem for further analysis. There has been no research comparing chemical composition of typical shards and shards which appear to be volcanogenic minerals as identified under a polarizing microscope. But, the difference ought not to be that large, as it is not illogical to believe that grains that basically have the same chemical composition, actually have the same chemical composition.

5.3. Chemical analysis

5.3.1. General discussion

Even if there are differences between different laboratories and instruments, the data from the same laboratory and instrument, and also between different laboratories and instruments, are tested by NIST-standard samples with known chemical composition (e.g. Jochum et al. 2011). In the current research the LA-ICP-MS-analysis were compared to two different NIST-standards after every fifth reading of the chemical composition of a grain. The standardized measurements make it possible to use chemical element data to find significant correlations of tephra horizons, even though there are still problems with the analyses. And, even if there are interlaboratory differences, any systematic error ought to be similar in most data from the same instrument, and therefore comparisons and correlations can always be performed.

The single test performed in the current research, comparing WDS and LA-ICP-MS, holds too little data to be of much use. No comparisons between LA-ICP-MS and WDS, for major elements, has been published, as far as I could find out. In other comparisons, e.g. the minor element Ba is measured as c. 10-100 times higher abundance in the WDS compared to the LA-ICP-MS (Kuehn et al. 2011).

As not many grains were analysed by LA-ICP-MS, and only three samples were chosen for

59 analysis by EDS, most supposed tephra horizons have not been confirmed or disproved by chemical composition. But, the little data which is available is still possible to use for discussion and some correlations. Similarly, any correlation with statistical significance with the “1641" eruption of Deception Island, and other published single samples, even though the current data do not contradict the possibility of correlation, is not trustworthy with only one sample that have grains with a strong signal (i.e. ML7 from Midge Lake), and old data (Aristarain and Delmas 1998, Palais et al. 1989).

5.3.2. WDS and LA-ICP-MS data

5.3.2.1. General, problems

The mounts for WDS and LA-ICP-MS were not polished very much, to try to avoid that any grains fell of in the process. Hence, sometimes only small parts of grains where visible at the surface of the mounts, and many WDS-analysis displayed a low total and were not used. But, even if the total were low, it was often possible to see if the grains could be shards or not. Grains which were probably shards, were marked for further analysis and confirmation with LA-ICP-MS. However, even if the mounts were only slightly polished, it was not easy to find the correct intensity for analysing small grains with the LA-ICP-MS. Quite a few grains popped almost instantly, as the laser light did hit them, and a few could not be found after transferring the mounts from the WDS to the LA-ICP-MS, and it was not possible to perform many measurements. At the end, only nine grains out of c. 30 grains, which were measured with LA-ICP-MS came out with a positive result. But, it is acknowledged that grains which are anisotropic may be shards.

To achieve a better result from the LA-ICP-MS, either the grains have to be larger (which is difficult, but not impossible, from these lakes), and/or the epoxy has to be made stronger (not sticky and with air bubbles inside, as with mount 3, etc.). The problems in LA-ICP-MS analysis which were found during analysis of small grains, have not been openly mentioned in the scientific literature (not as far as was found in the literature referred to in the current work).

5.3.2.2. Single grain analysis

From the WDS analysis, it is shown that LA-135 from Lake Boeckella has a SiO2-content of only 35%, and a FeO-content of 22%. Hence, this show that this grain probably is a volcanic Fe-mineral grain and not a shard. And, almost the same holds for LA-110, even though this grain has some more similarities to a shard as it contains more elements. But, grain LA-110 from Lake Boeckella is interpreted as a Fe-mineral and not a shard. Grain LA-97 from Hidden Lake do not fit in with any volcano. It is uncertain that grain LA-97 is a shard, because it sits very low down in the classification of grains as possible shards, and MgO and

TiO2 are missing from the grain (Appendix 3). It may be concluded that LA-97 is a feldspar.

Grains LA-122 is from Lake Boeckella, and LA-131 is from Hidden Lake. Both these grains have a very high sodium content, 13.46% and 14.58% respectively (table 5), which may indicate that they are similar to volcanogenic feldspar grains, even if they in other respects display a composition with many elements, similar to a shard. The highest sodium content in tephras, found from a literature search from many other volcanoes, is less than 10% (i.e. values in A6 and A12, table A5:3, Appendix 5 and Supplementary material on CD).

60 Commonly the sodium content is c. 6% or less in volcanic shards.

Grain LA-133 from lake Boeckella, has a low total of 82.6%, but it appear to be a shard in all instances. The grains LA-36, LA-38 and LA-39 from Midge Lake are all perfectly similar to shards.

There were too few grains available for more than a test of the methodology of analysis by LA-ICP-MS, even though the three Midge Lake shards (ML1) clearly were shards and displayed the same chemical composition as eruptives from Deception Island. At any rate, the results and discussions using the “logistics” tree and diagrams (figs. 8-11) from Kraus et al. (2013, in press), concerning single grains, are only included to describe how the methodology work, showing “pros and cons” in the process. And, it was shown that the “logistics” tree may give a different result than the scatter diagrams, i.e. grains in the current research were mistakenly correlated with Bridgeman Island instead of with Deception Island.

5.3.3. EDS data

5.3.3.1. General

The EDS data folds out more information than from the nine grains analysed by LA-ICP-MS. But, it is not as easy to separate and correlate tephras based only on major elements and no trace elements, and the EDS only measure major elements.

Many different scatter diagrams displaying different chemical compositions were chosen for comparison of EDS-analyses. This was done in order to eliminate the possibility that one single diagram, by chance, could be used for correlation even though most of the data show something else. E.g., if only the diagrams in figs. 16, 18 and 19 are used, or more so - only the diagram in fig. 19, the conclusion will be different compared to if all diagrams are used (see discussion below).

Kraus et al. (2013, in press) reported analytical data from in situ outcrops/sediments directly from the source volcanoes. It is highly improbably that these collected samples are contaminated with tephras from different eruptions and/or volcanoes. Hence, single grain analyses was not necessary to publish, if most grains/samples had the same chemical composition. The methods used by Kraus et al. (2013, in press), WDS for major elements and ICP-MS for trace elements, are comparable to the methods used in the current research, even if there may be some instrumental and interlaboratory differences (see in Introduction, Analyses of major, minor and trace elements). The data points published by Kraus et al. (2013, in press) are therefore a good source for identification and correlation of tephras. But, even if Kraus et al. (2013, in press) sampled tephras from most formations on Deception Island, he did not include information about which sample came from which formation. This is a shortcoming, as it is not possible to correlate tephras with different eruptions from Deception Island. Also, Deception Island eruptives may be both similar and different, during the same or different eruptions, displaying the largest compositional differences of all volcanoes in the area. Therefore it is not possible to make more than a general correlation with Deception Island, nor to make any statistical comparisons. The data published by Smellie and others from Deception Island are mainly bulk samples, and can not be used other than for general correlations (Appendix 5, table A5:2, no. 31-46 compare to the age spectra of the current research; Smellie et al. 1992, Fretzdorff and Smellie 2002, Smellie

61 2002a, Smellie and Millar 2002).

5.3.3.2. Midge Lake

It is clear from figs. 12-19 that sample ML7 is bimodal, similar to tephras from King George Island (Lee et al. 2007). However, there is no possibility to correlate the two lakes, because of reworking in King George Island lakes. The differences in chemical composition between the lakes (see Results and figs. 12b-19b) may be a result from transport distance, laboratory procedures or that the tephras have been contaminated with grains from different volcanoes. The statistical data which Lee et al. (2007) used for correlation with Deception Island did not arrive at a highly significant result. But, Deception Island appear to be the best, maybe the only, alternative to explain the origin of the absolute largest parts of the tephras in both lakes. It is not known if the bimodal distribution of the MgO-content has any meaning (figs 17a-b).

More evidence for a bimodal eruption was found in marine sediments by Moreton and Smellie (1998) and Fretzdorff and Smellie (2002).

5.3.3.3. Lake Boeckella and Hidden Lake

The Lake Boeckella shards display a very large compositional spread of the data. It is because of that reason not possible to correlate this lake with any other place by the help of the chemical composition. According to the process of following the “logistics” tree by Kraus et al. (2013, in press) for the LA-ICP-MS data, some grains were from Bridgeman Island (even though a more rigorous analysis showed that the grains are more similar to eruptives with a chemical composition similar to those from Deception Island). Could some ash sampled on the Antarctic Peninsula be from Bridgeman Island? This island is not far away, and it is geographically in about the correct place for ashes to be transported to Lake Boeckella and Hidden Lake, as the general wind direction from Bridgeman Island is approximately correct. Maybe there could have been a larger unknown eruption here during the last hundreds of years? Or, have there been many unknown smaller eruptions? Active fumaroles have been observed from 1821-1850 on Bridgeman Island (Weaver et al. 1979). Or, has there been an eruption from some other volcano in Antarctica which could deposit ashes in the research area (e.g., see Global volcanism program 2012a)?

There is a time span of almost 500 years of possible volcanism, most which probably is unrecorded by human observations, that is in the same time span as the tephras sampled in the lakes for the current research. And almost all volcanogenic samples collected by Kraus et al. (2013, in press) were fresh.

Observations of volcanic activity have been observed on a few occasions on Seal Nunataks, during, e.g., recent overflights with airplanes (Kraus and Kurbatov 2010, Kraus et al. in press 2013). Seal Nunataks actually are composed of sixteen different volcanoes with probably some differences in their chemical compositions. Also, ash from volcanoes thousands of kilometers away, e.g. the Andes and West Antarctica, have been deposited in the Antarctic ice. Tephras from West Antarctica have a very large spread in the compositional data, as is also the case for the samples from Lake Boeckella and Hidden Lake. Tephras from West Antarctica also display a much larger grain size than from the current research. Shards display a mean grain size of 91 µm, c. 200 km from Livingston island, after a transport

62 distance of c. 3000 km (Hillenbrand et al. 2008), while those in the current research have a mean grain size much less than 40 µm after a transport distance of only c. 40-200 km (Appendix 1, table A1:7; i.e. 80-90% of the grains from the current research are between 20- 40 µm in size). There should be no difficulties for grains from West Antarctica to be transported to the Antarctic Peninsula, but at least the tephras close to Byers Peninsula are believed to be very much older than the sediments in the lakes in the current research (see Introduction, Area description and earlier work, and figs. 12-19 in this work). Another possible source of tephra is Peter I Island, c. 1400 km to the southwest of Lake Boeckella and Hidden Lake (Hart et al. 1995, Global Volcanism Program 2012b).

The only historically recorded larger eruptions in the research area are from Deception Island. But the chemical compositions of the eruptives from this volcano are much more narrow than displayed by the tephras from Lake Boeckella and Hidden Lake. Hence, it is very difficult, I would say almost impossible, to hold on to an interpretation that most shards in Lake Boeckella and Hidden Lake are from Deception Island.

A more likely interpretation of the data is, that the large spread indicate that the tephra horizons may have been built up by a mix of shards from different ash falls - both from Deception Island eruptions with different compositions and from other volcanoes within c. 6000 km (or longer) distance from Lake Boeckella and Hidden Lake. The shards from such ashfalls have of course partly been deposited on land (i.e. the largest part of most islands), from many volcanic eruptions during a long time period of maybe thousands of years, and have been quickly released to the lake bottoms mostly during recent heavy snow melting or rainstorms. And, in Lake Boeckella there is a high rate of sediment deposition. There are glaciers near by, within 100 meters from Lake Boeckella, and glacier ice is a good storage for ashes. And, ash stored in glacier ice do not weather very quickly. Maybe some grains could have been stored for even 100 000 years or so, and have added variation to the chemical composition of grains in Lake Boeckella? Similarly, grains in tills from the Weichselian glaciation are still fresh, not weathered at all (Molén 1992). And, if the pretreatment process of the grains, using strong acids, would change something, it would maybe dissolve softer weathered parts of grains easier than fresh grain surfaces, and, hence, old grains may even in some ways appear to be fresher after rather than before the pretreatment process which have been used in the current work (e.g. some fresh shards have a very irregular appearance, similar to the general appearance of some grains that are heavily weathered; see a few grains in the photos in Sarna-Wojkicki 2000 and one photo in The twelve soil orders 2012).

The data from Hidden Lake is varying in a similar way as the data from Lake Boeckella, but usually display less variation in chemical composition. This may indicate that Hidden Lake is further away from volcanoes that may have erupted recently, during the last thousands of years.

5.3.3.4. FeO/MgO and SiO2 - alternative interpretations?

In the MgO compared to SiO2-diagram (fig. 16) and MgO compared to CaO diagram (fig. 18), the chemical composition of the shards from the three analysed lakes are not so much spread out. The Midge Lake shards are still mainly in two groups, but Hidden Lake shards and especially the Lake Boeckella shards are grouped closer to Deception Island than in figs. 12- 15. In figs. 16 and 19 Hidden Lake has a greater variation in chemical composition than Lake

Boeckella. It is especially evident in the FeO/MgO compared to SiO2-diagram (fig. 19), that

63 Lake Boeckella grains are sorted with the few WDS-analysed grains in one group, and the EDS-analysed grains in almost the same area of chemical composition as Deception Island. If only the diagrams in figs. 19a-19b are used for correlation, the Lake Boeckella grains could be interpreted as mainly bimodally sorted in a similar way as the ML7 grains, i.e. originating from Deception Island. However, when comparing the analytical data from all the diagrams, this interpretation is very unlikely. Lake Boeckella is also almost bimodal for CaO, which ML7 is not (fig 18b). The Lake Boeckella grains display a chemical composition that varies more than all other analysed samples in the area.

Hidden Lake shards commonly display e.g. the same FeO/MgO-ratio (fig. 19b), but different

SiO2-content (the last fact seen in all diagrams, but easiest observed in fig. 19b). Hence, the

Hidden Lake shards are divided in two groups, <56% and >63% SiO2. This may also be interpreted to be from a bimodal eruption. But, the data in total, from all figures 12-19, and considering that this is only one sample with only 12 grains, the interpretation of ashes from a bimodal eruption observed in Hidden Lake is not much more than a speculation. The varying chemical composition of the Hidden Lake grains may be more an effect of lagtime and quick release of old shards during snow melting, similar to the interpretation of the Lake Boeckella shards. At Hidden Lake there are glaciers even at the shore of the lake, which could release large amounts of old ashes during e.g. warm summers.

5.3.3.5. Pretreatment of samples and spread of data

An alternative interpretation of the large spread in the data of the chemical composition for Lake Boeckella and Hidden Lake, may be found in the fact that for EDS analysis the grains are not polished (e.g. Kuehn and Froese 2010 described variation in element abundance before and after polishing small grains). Could it be possible that the pretreatment of the grains, with e.g. H2O2, may have dissolved certain of the oxides in the grains, and not the others, to make the large spread of the data? The surfaces of the grains are the parts which have been treated with strong acids and are analysed, as nothing have been polished away. But, there is no consistency in the data from the EDS analyses, no oxide which have been dissolved more than the others. The spread of almost all the element oxide ratios is larger, for both Lake Boeckella and Hidden Lake, than almost all other volcanoes in Antarctica together, i.e. the volcanoes which have been documented here (see earlier in Discussion and Results, above). And, opposite to these two lakes, Midge Lake data is very much sorted into two separate groups. If the pretreatment process would dissolve grain surfaces at different rates it should also show up in grains from Midge Lake, because all samples have been pretreated in the same way. But, nothing peculiar show up in the unpolished Midge Lake grains. Of course, it is not possible to know if a single grain or two have been dissolved so that the oxide ratios of the surfaces of some grains have changed. But, we may conclude that if anything of large significance has been dissolved in the pretreatment process, it does not show up in differences in the data, and all changes must have been almost similar in all grains in all samples so that they can not be easily detected.

It may also be speculated that the small beam used for EDS (200 nm), compared to the large beam used for WDS (10 µm), analysed small parts of the grains which were inhomogeneous, similar to the grains from Yemen and Ethiopia mentioned in the introduction (Ukstins Peate et al. 2008). But, still, if so, if the grains originated from the same volcano, the grains from Midge Lake would show the same pattern as Lake Boeckella and Hidden Lake, and this is not the case.

64 5.4. Hypothetical age correlations from depth of tephra horizons

As it has not been possible to correlate any of the samples from the three lakes with eachother or with Deception Island, more than in a general way, only the depth-age relationships in the sediment cores can be used (table 1 and Appendix 1). Also, there is so little data or no data from most horizons, that it is not possible to say anything for certain about chemical correlations. Data from Lake Boeckella and Hidden Lake display so much variation, that it is not possible to correlate with any other lake or volcano. Midge Lake display a chemical composition which, in general, is similar to the chemical composition of Deception Island, and also to other tephras in the area that have been correlated with Deception Island, i.e. Hurd Peninsula and King George Island. But, the shortage of detailed data available from the source volcano preclude a correlation with a special eruption.

To be sure of the age of a tephra horizon, either we need a real good correlation with a known eruption from Deception Island (or any other volcano), but no one have published any such data, or, we need another dating method. C-14 has many problems (as outlined earlier, e.g. Zale 1994a). Maybe the amino acid method could be used for Lake Boeckella, which have a lot of organic material in the bottom sediments? And there are many other methods. The problem is that most methods are relative, even those which are usually believed to be absolute, and there are many shortcomings in the methods (e.g. Mahaney 1984, 1991).

The only secure way of dating is a direct correlation with the help of the chemical composition of a tephra horizon and a historically dated eruption of known age from Deception Island (or some other volcano), and this data is not available. The correlations and age suggestions below are indefinite, but not more can be done with the current data quantity. We can not know for sure if e.g. the deposition of tephra was delayed for a long time, similar to the tephra deposition in a lake in northern Sweden (Davies et al. 2007), but even if Lake Boeckella has soft organic rich bottom material (Zale 1993), it is not possible that shards could have sunk down very much (Rolf Zale, pers. comm. 2012) (e.g., compare to Enache and Cumming 2006).

Midge Lake. Identified tephra horizons (table 6): • ML1 is at the top of the sequence in the sediment core, and therefore is probably correlated with the latest eruptions at Deception Island, in 1967-1970 AD, and then probably the 1967 eruption (Pallàs et al. 2001, and table A5:1 in Appendix 5). That is also what the interpolated age is showing (table A1:1 in Appendix 1). There may have been a shortage of sediment deposited in this lake lately, similar to “Lake Åsa” close by, which may explain why this tephra horizon is at the most surficial layer. The sedimentation rate in “Lake Åsa” was considered to formerly be higher than in other Antarctic lakes, but nonexistent today because it is too shallow (Björck et al. 1991a). (There are some more recent uncertain eruptions on Deception Island, in 1972 and 1987, but it very speculative to refer ML1 to these eruptions which maybe even did not take place, and if they did they must have been very small (Global volcanism program 2012c). • ML5 could be correlated either with the second of the tephras identified by Hodgson et al. (1998) or with AP1. It is not possible to know, as there is no chemical data available. The interpolated age is c. 1700, which would correlate this horizon with AP1. • ML7 is probably correlated with AP2, as this horizon is recorded in work by two other researchers, and it is not a cryptotephra (pers. comm. Rolf Zale 2012). The interpolated

65 age is c. 1550 AD, which is close to AP2.

Lake Boeckella. Identified tephra horizons (table 6): As there is a very large background population in this lake, many samples were counted twice, to verify if they were tephra horizons or not. For LB10-20, LB10 was counted three times and LB20 was counted two times, LB60 was counted twice, and for LB88-89 sample LB88 was counted twice. • LB10-20 has an interpolated age between c. 1910-1950 (table A1:2, Appendix 1), which correlates well with the 1912-1917 AD eruptions of Deception island. But, of course, no correlation is statistically significant with the little data available. • LB60 has an interpolated age of c. 1725 AD, which correlates well with AP1. But, LB60 is only a single sharp tephra peak, with no extra lag effect for this peak, as is common for tephras in lakes. It may be suggested that this peak is a deposit from a rainy day, just a lag effect in itself, and has no connection to any simultaneous volcanic eruption. • LB88-89 has an interpolated age of c. 1550 AD, which correlate with AP2. The spread in the chemical composition data make it impossible to correlate this horizon with any other tephra or horizon.

Hidden Lake. Identified tephra horizons (table 6): • HL8 has an interpolated age of c. 1860 AD (table A1:3, Appendix 1), which may correlate with the 1842 eruption of Deception Island (table A5:1, Appendix 5). But, no correlation is definite with the little data available. • HL17 has an interpolated age of c. 1700 AD, which correlate well with AP1, even if correlation is not definite with the little data available. • HL29 has an interpolated age of c. 1480 AD, which correlate well with AP2. But it is not possible to correlate with the help of the chemical composition of this sample, as the variation in the data is too large.

Table 6. Tephra horizon chronology and correlations in the Antarctic Peninsula area. This table is similar to table 1 , but only including the part of the age spectra where it is possible that there are tephra horizons from the current research, and only from the lakes in the current research. X is “tephra horizon is present”, multiple X:es is that the tephra is interpreted as repeated. Tephras y ounger than AP1 were not recorded when this chronology was constructed. The columns marked with CR are from the current research. (A = Hodgson et al. 1 998. B = Björck et al. 1 991 a. C = Björck and Zale 1 996a.) Age, C-1 4 BP Tephra Midge Midge Midge Lake Bo- Lake Bo- Hidden Hidden and appr. AD horizon Lake (A) Lake (A, Lake eckella eckella Lake (B) Lake cal. y ears B, C) (CR) (B) (CR) (CR)

-20/1 967 - X, 2-3 cm ML1 1 97 0? acidic

33-1 1 0/1 842 X, 3-4 cm ML5? LB1 0-20 HL8 or 1 91 2-1 91 7 ?

250/1 7 00 AP1 ML5? LB60 X, 1 2 cm HL1 7

450/1 500 AP2 X, 8-9 cm X, 7 cm ML7 X LB88-89 X, 28 cm HL29

7 50- AP3 X, 1 5-1 6 X, 1 2 cm XX, c. 800/1 200 cm 40 cm

66 6. Conclusions

6.1. Current research

Even though there are many shortcomings in the area of tephrochronology, the current methods are the only available, and many significant results are documented. As the international tephrochronology community is standardizing the procedures, more data will be available for correlations in the future. A good sign of this is the work by Kraus et al. (2013, in press).

Volcanogenic mineral grains may be used in grain size analysis and in identification of tephra horizons, especially in cryptotephras where there are problems with identification of volcanogenic grains. Mineral grains are easier observed in a polarizing microscope than are shards.

The chemical analyses displayed, what is not, or very seldom is, reported in the scientific literature, that some grains with optical properties similar to volcanogenic mineral grains turned out to be shards, some had a chemical appearance of being shards with compositions similar to some minerals (e.g. c. 14% sodium), and about 50% of all supposed shards with optical properties similar to shards turned out to be minerals.

WDS followed by LA-ICP-MS is a method with many laboratory set ups which have to be followed, of which some problems have been outfolded here, i.e. identification of shards, transfer of samples from one instrument to another, importance of gluing grains correctly and having a laser beam of correct size and intensity. And, EDS may be a simpler method to use, instead of WDS.

The analysis of the nine grains with LA-ICP-MS show that the methodology of analysis work well (following Kraus et al., 2013, in press), even though there are some loopholes if grains have special compositions and can be wrongly placed in the “logistics” tree diagram. Even though only three shards from sample ML1, the most recent sample from Midge Lake, could be analysed, these correlated very well with other samples with similar age and origin, e.g. samples from Deception Island and Hurd Peninsula.

The EDS data showed that Midge Lake samples are correlated with Deception Island, and sample ML7 is bimodal. No other correlations, based on chemical compositions, are possible. It is too little data, no specific data from different eruptions on Deception Island, and too much spread in the available data. The large spread in the chemical composition data for Lake Boeckella and Hidden Lake may indicate long lag times and mixing of grains from many volcanoes/eruptions. Both lakes are close to glaciers, as opposed to Midge Lake. In Lake Boeckella the distribution of shards are very similar to a small Swedish lake where there is permanent snow close by, i.e. there is no sharp tephra peaks, but ashes are deposited during an extended time period (Davies et al. 2007).

It is important to compare many element abundances, if there are similarities/differences in some chemical compositions but not in others, as has been done in figs. 8-19 in the current research. Otherwise one single element ratio may change the interpretation, even though the total chemical composition of grains show something else. E.g., a) the analysis of the LA-ICP- MS data may lead to a wrong interpretation, if the Sr/Nb-ratio is used as a start, and, b) the

67 EDS data may lead to a wrong interpretation if only the FeO/MgO-ratio is compared to the

SiO2 content, as is shown in this work.

Because of the problems in methodology that has not been reported in the scientific literature, and in specific data reported from other researchers from e.g. volcanoes, there was a shortage of analytical data. Therefore the age correlations performed in this work are not more definite than earlier datings and correlations, made by other researchers (e.g. Zale 1993).

6.2. Suggestions for future research

1. To see if there is any variation in the chemical composition of different parts of grain surfaces, grains from the current research may be analysed by EDS on many different spots of the surfaces. This will in a straightforward way show if the grains display heterogeneous surfaces or if the grains actually are very different in chemical composition. If it can be shown directly if the pretreatment process have changed the chemical composition of the surface of the grains, the grains have to be polished and analysed a second time by EDS or WDS. 2. More grains from the Lake Boeckella and Hidden Lake may be analysed by EDS and also LA-ICP-MS, to see if different volcanoes or eruptions can be identified. It may be necessary to analyse 50-200 grains, before there is a statistically significant pattern in the data. To find a correlation with a special eruption, it is necessary to know exactly from what eruption a sample is from, e.g. ashes collected at the volcano in question. 3. All possible nine tephra horizons recorded in the current research ought to be analysed with EDS/WDS and LA-ICP-MS, to find possible correlations with volcanoes and other tephras. 4. Tephra samples from Deception Island and other volcanoes have to be precisely dated. Single shards have to be chemically analysed, and the data has to be published, so that it will be possible to make exact correlations with tephra horizons in lakes and glaciers in Antarctica. 5. Typical isotropic shards, and anisotropic shards which appear to be volcanogenic mineral grains, may be compared for chemical composition. This may show differences, which may be used in correlations. 6. It may be important to conduct research concerning melting points of major and trace element oxides, and their connection to different eruptive and fractional processes in the area of tephrochronology (e.g. incompatible elements like lanthanides are more common in low temperature melts, and there are often large differences between ICP-MS and WDS for major element oxides which have high melting points). One may also, in a research project like this, speculate about if MgO, with a very high melting point temperature of c. 28500C, could in some way be responsible for the results in figs. 16 and 18-19, where the shards from Hidden Lake, but especially from Lake Boeckella, display, for this oxide, a chemical composition that does not vary very much, while the EDS data from Midge Lake (ML7) was almost bimodal.

7. Acknowledgments

The following researchers have provided me with help in different ways: Rolf Zale and Per Hörstedt at the University of Umeå, Tod Waight and Alfons Berger at the University of

68 Copenhagen, Thomas Find Kokfelt and a laboratory technician at GEUS, Copenhagen, Stefan Kraus at the Chilean National Service of Geology and Mining - SERNAGEOMIN, John L. Smellie at the University of Leicester, and David J. Lowe at the University of Waikato.

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76 9. Appendices

Appendix 1. Grain size analysis, tephra horizon identification, and statistical analysis Appendix 2. Subsample description for WDS, LA-ICP-MS and EDS analysis Appendix 3. Grouping of WDS-analysis-data in shards/minerals Appendix 4. Instruments/methods used in tephrochronology for chemical and other analysis Appendix 5. Examples of earlier published geochemistry data from tephras, mainly from the research area Appendix 6. Different statistical methods used in tephrochronology work

Appendix 1. Grain size analysis, tephra horizon identification, and statistical analysis

Grain size analysis and volcanogenic grain concentration measurements were conducted on volcanogenic mineral grains with a polarizing microscope, with two polarizers. Mineral grains show up more easily than shards, as they light up white or slightly gray under double polarizers, while shards become dark under double polarizers and are therefore difficult to notice.

To verify if there was a surplus of volcanogenic mineral grains (i.e. possibly tephras), and if the hand counting of grains was incorrect, the following samples were hand counted twice: LB1, LB20, LB41, LB47, LB60, LB63, LB79, LB80, LB87, LB88. The following samples were hand counted three times or more: LB10, LB27.

Sample LB10 was included in the chemical element analysis, to see if there was an identifiable backlag of grains following after the tephra layer which begins at LB20, or if the grains had a possible different volcanic source, either a different volcano or a different eruption from the same volcano (e.g. compare to Davies et al. 2007). Sample LB20 was missing, and therefore sample LB18 was used instead.

77 Legend and explanation for all tables, A1 :1 -A1 :3.

The age -37 y ears is 1 987 , the y ear of sampling of the lakes (C-1 4 BP starts with zero at 1 950 AD). The other y ears are interpolated from C-1 4-dating that has been done in other places. The first columns, A-E and Total sum, are the number of observ ed and measured grains in the microscopic subsamples. The later columns, A-E and Total konc., are the calculated number of grains per g dry mass. This was calculated from the weight of the subsamples, and how much the subsamples were diluted, during preparation for grain size analy sis (see Supplementary material, on CD).

Approximate grain size interv als: A = 21 -40 µm, B = 41 -60 µm, C = 61 -80 µm, D = 81 -1 00 µm, E = more than 1 00 µm.

Table A1 :1 . Grain size analy sis of Midge Lake, raw data. Confident or almost confident tephra tops, one standard dev iation, are marked with bold (ML1 , ML5 and ML7 ). See discussion about confidence lev els in table A1 :4. Samples ML1 1 and ML1 2 are in the table only because sample ML1 2 has an interpolated date of correlation based on a C-1 4 date (Björck et al. 1 991 a). The C1 4-age for horizon no. 1 2 and the age for horizon no. 1 are from Rolf Zale, and the other approximate interpolated ages are by me.

Sample, Sed. Age A B C D E Tot. A B C D E Total ML1- depth 14C BP sum. konc. ML12 cm no. no. no. no. no. no. no. dry no. dry no. dry no. dry no. dry no./g dry mass 1 0-1 -37 305 22 10 4 0 341 340160 24536 11153 4461 0 380311 2 1 -2 50 1 43 4 3 1 0 1 51 223826 6261 4696 1 565 0 236348 3 2-3 1 20 234 25 4 4 0 267 2557 05 27 31 9 437 1 437 1 0 291 7 66 4 3-4 1 90 21 2 0 0 0 23 1 1 280 1 07 4 0 0 0 1 2354 5 4-5 260 214 31 10 3 2 260 290915 42142 13594 4078 2719 353448 6 5-6 330 27 4 1 0 0 32 45855 67 93 1 698 0 0 54347 7 6-7 400 28 3 0 0 0 31 298723 32006 0 0 0 330729 8 7 -8 47 0 1 86 20 3 0 0 209 21 1 07 8 22697 3404 0 0 237 1 7 9 9 8-9 540 1 43 1 7 7 1 2 1 7 0 1 92990 22943 9447 1 350 2699 229428 1 0 9-1 0 61 0 1 29 1 0 0 0 0 1 39 235239 1 8236 0 0 0 25347 5 1 1 1 0-1 1 680 1 2 1 1 -1 2 7 55+-105

78 Table A1 :2. Grain size analy sis of Lake Boeckella, raw data. Confident or almost confident tephra horizons, two standard dev iations, are marked with bold (LB1 0-LB20, LB60 and LB88-LB89). See discussion about confidence lev els in table A1 :5, and about the tephra horizons, in Discussion. The C1 4-age is interpolated by Rolf Zale (unpublished).

Samples Sed. Age A B C D E Tot. sum. A B C D E Tot. LB1- depth cm 14C BP konc. LB89 no. no. no. no. no. no. no. dry no. dry no. dry no. dry no. dry no./g dry mass 1 0-1 -37 246 32 5 1 1 285 1 020349 1 327 28 207 39 41 48 41 48 1 1 821 1 2 2 1 -2 -30 36 6 1 1 0 44 291 491 48582 8097 8097 0 356267 3 2-3 -25 1 28 1 2 1 0 0 1 41 869609 81 526 67 94 0 0 957 929 4 3-4 -22 41 4 69 4 1 0 488 582541 97 090 5628 1 407 0 686667 5 4-5 -20 31 9 45 1 0 0 0 37 4 7 25340 1 02321 227 38 0 0 850398 6 5-6 -1 5 497 7 5 1 3 2 0 587 81 531 5 1 23035 21 326 3281 0 962957 7 6-7 -1 2 41 7 49 6 2 0 47 4 67 647 1 7 9489 97 33 3244 0 7 68939 8 7 -8 -1 0 21 9 36 5 1 0 261 1 1 5827 1 1 90401 26445 5289 01 380406 9 8-9 -5 238 53 2 0 0 293 620858 1 38258 521 7 0 0 7 64334 10 9-10 0 645 94 7 2 1 749 1330188 193857 14436 4125 20621544668 11 10-11 5 910 87 12 1 0 1010 1115054 106604 14704 1225 0 1237588 12 11-12 13 223 47 12 3 2 287 333819 70357 17963 4491 2994 429624 13 12-13 15 996 87 12 1 1 1097 1288811 112577 15528 1294 1294 1419504 14 13-14 20 952 129 7 2 0 1090 1328470 180013 9768 2791 0 1521043 15 14-15 22 820 66 13 1 0 900 993440 79960 15750 1212 0 1090361 16 15-16 26 925 116 20 3 1 1065 1035089 129806 22380 3357 1119 1191751 17 16-17 30 978 73 8 1 0 1060 1264788 94406 10346 1293 01370834 18 17-18 33 837 66 11 0 1 915 1532998 120882 20147 0 18321675858 19 18-19 35 627 104 19 2 0 752 1034443 171582 31347 3300 01240672 20 19-20 40 1311 95 14 3 0 1423 1778141 128851 18989 4069 01930049 21 20-21 45 1 28 5 0 0 0 1 33 898359 35092 0 0 0 933451 22 21 -22 50 48 1 4 3 1 2 68 3007 97 87 7 33 1 8800 6267 1 2533 4261 29 23 22-23 54 1 6 6 0 0 0 22 1 337 42 501 53 0 0 0 1 83896 24 23-24 58 20 5 0 0 1 26 1 551 42 387 86 0 0 7 7 57 201 685 25 24-25 60 26 0 0 0 0 26 224998 0 0 0 0 224998 26 25-26 65 1 3 0 0 0 0 1 3 87 380 0 0 0 0 87 380 27 26-27 7 0 1 0 0 0 0 1 827 3 0 0 0 0 827 3

79 Table A1 :2 (cont.) 28 27 -28 7 4 1 2 3 0 0 0 1 5 87 060 21 7 65 0 0 0 1 08825 29 28-29 7 9 7 2 4 0 0 0 7 6 51 347 8 28527 0 0 0 542004 30 29-30 80 33 2 0 0 0 35 231 634 1 4038 0 0 0 24567 3 31 30-31 86 398 47 6 0 0 451 6627 31 7 8262 9991 0 0 7 50984 32 31 -32 90 64 3 1 0 0 68 385691 1 807 9 6026 0 0 4097 97 33 32-33 95 1 58 1 1 2 0 0 1 7 1 57 47 1 3 4001 2 7 27 5 0 0 621 999 34 33-34 1 00 332 30 2 1 0 365 564602 51 01 8 3401 1 7 01 0 6207 22 35 34-35 1 02 46 7 2 0 2 57 1 7 1 07 8 26034 7 438 0 7 438 21 1 988 36 35-36 1 06 321 41 8 2 1 37 3 7 53035 961 82 1 87 67 4692 2346 87 5022 37 36-37 1 1 2 469 40 1 1 2 0 522 7 86455 67 07 5 1 8446 3354 0 87 5330 38 37 -38 1 1 9 360 1 1 2 0 0 37 3 57 2285 1 7 486 31 7 9 0 0 592951 39 38-39 1 21 460 22 2 0 0 484 567 7 1 1 27 1 51 2468 0 0 597 331 40 39-40 1 25 54 7 0 0 0 61 1 02855 1 3333 0 0 0 1 1 61 88 41 40-41 1 29 266 41 6 6 0 31 9 4227 1 2 651 55 9535 9535 0 506937 42 41 -42 1 32 433 32 2 1 0 468 67 097 4 49587 3099 1 550 0 7 25209 43 42-43 1 39 247 1 3 5 0 0 265 37 3825 1 967 5 7 567 0 0 401 068 44 43-44 1 45 47 5 46 1 3 0 0 534 7 37 220 7 1 394 201 7 7 0 0 8287 91 45 44-45 1 50 561 1 43 20 4 1 7 29 91 8562 2341 43 327 47 6549 1 637 1 1 93640 46 45-46 1 53 382 34 7 0 0 423 608663 541 7 4 1 1 1 54 0 0 67 3991 47 46-47 1 59 469 38 3 2 0 51 2 7 57 1 66 61 348 4843 3229 0 826586 48 47 -48 1 64 37 6 34 6 2 0 41 8 48047 6 43447 7 667 2556 0 5341 47 49 48-49 1 68 557 1 07 1 3 4 0 681 826245 1 587 22 1 9284 5934 0 1 01 01 84 50 49-50 1 7 2 47 6 49 1 1 1 0 537 57 2991 58984 1 3241 1 204 0 646421 51 50-51 1 7 9 21 4 24 7 3 1 249 325434 36497 1 0645 4562 1 521 37 8660 52 51 -52 1 83 43 7 1 0 0 51 1 57 7 81 25685 3669 0 0 1 87 1 35 53 52-53 1 89 21 0 8 2 0 0 220 24831 4 9460 2365 0 0 2601 39 54 53-54 1 92 1 88 1 7 8 2 0 21 5 2957 26 267 41 1 2584 31 46 0 3381 97 55 54-55 1 97 27 7 37 1 1 2 0 327 404382 5401 5 1 6059 2920 0 47 7 37 6 56 55-56 203 283 26 9 2 1 321 47 841 0 43953 1 521 4 3381 1 690 542648 57 56-57 209 294 35 1 1 3 1 344 452965 53924 1 6948 4622 1 541 530000 58 57 -58 21 2 220 1 3 1 1 0 235 47 5368 28090 21 61 21 61 0 507 7 7 9 59 58-59 21 9 237 6 2 0 0 245 363263 91 97 3066 0 0 37 5525 60 59-60 224 666 67 17 1 3 754 1474701 148356 37643 2214 66431669557 61 60-61 229 31 2 34 5 3 0 354 394458 42986 6321 37 93 0 447 558 62 61 -62 232 606 59 22 9 2 698 69091 4 67 267 25083 1 0261 2280 7 95805 63 62-63 235 387 55 1 2 5 2 461 4401 06 62547 1 3647 5686 227 4 524261 64 63-64 240 1 46 20 7 4 1 1 7 8 230926 31 634 1 1 07 2 6327 1 582 281 540

80 Table A1 :2 (cont.) 65 64-65 249 337 51 1 0 5 3 406 67 5603 1 02243 20048 1 0024 601 4 81 3931 66 65-66 255 283 38 1 9 7 0 347 47 4260 63682 31 841 1 1 7 31 0 581 51 4 67 66-67 259 357 34 1 6 3 2 41 2 444046 42290 1 9901 37 31 2488 51 2457 68 67 -68 263 542 46 1 3 4 0 605 627 846 53286 1 5059 4634 0 7 00824 69 68-69 269 37 1 54 1 2 2 4 443 484565 7 0530 1 567 3 261 2 5224 57 8605 7 0 69-7 0 27 3 340 7 0 1 4 8 3 435 487 901 1 00450 20090 1 1 480 4305 624227 7 1 7 0-7 1 27 9 31 5 44 5 3 0 367 37 291 4 52090 591 9 3552 0 43447 4 7 2 7 1 -7 2 285 298 49 1 9 8 0 37 4 36897 6 6067 1 23525 9905 0 46307 7 7 3 7 2-7 3 290 47 3 50 1 3 2 0 538 628594 66448 1 7 27 6 2658 0 7 1 497 6 7 4 7 3-7 4 299 457 49 1 2 3 2 523 524395 56226 1 37 7 0 3442 2295 6001 28 7 5 7 4-7 5 304 660 7 6 29 6 1 7 7 2 1 0051 20 1 1 57 41 441 64 91 37 1 523 1 1 7 5685 7 6 7 5-7 6 31 0 383 47 8 1 0 439 568339 697 44 1 1 87 1 1 484 0 651 438 7 7 7 6-7 7 31 5 248 33 7 1 1 290 605408 80558 1 7 088 2441 2441 7 07 937 7 8 7 7 -7 8 320 1 7 2 22 1 0 3 0 207 340230 4351 8 1 97 81 5934 0 409462 7 9 7 8-7 9 329 41 8 41 5 3 0 467 7 90800 7 7 566 9459 567 6 0 883501 80 7 9-80 335 434 39 8 3 0 484 9851 60 88528 1 81 60 681 0 0 1 098658 81 80-81 340 284 20 5 0 0 309 531 357 37 420 9355 0 0 57 81 31 82 81 -82 349 449 41 9 3 0 502 7 1 301 2 651 08 1 4292 47 64 0 7 97 1 7 6 83 82-83 355 27 3 24 1 1 1 0 309 491 81 5 43237 1 981 7 1 802 0 55667 0 84 83-84 362 499 51 1 2 6 1 569 693056 7 0833 1 6667 8333 1 389 7 9027 8 85 84-85 369 444 34 1 2 2 0 492 7 047 29 53966 1 9047 31 7 4 0 7 8091 5 86 85-86 37 5 21 3 1 7 7 1 0 238 459595 36681 1 51 04 21 58 0 51 3538 87 86-87 380 327 48 7 4 3 389 57 1 223 83849 1 2228 6987 5241 67 9529 88 87-88 389 576 95 17 4 3 695 1061628 175095 31333 7372 55291280957 89 88-89 395 416 122 21 11 5 575 880627 258261 44455 23286 10584 1217212

81 Table A1 :3. Grain size analy sis of Hidden Lake, raw data. Confident or almost confident tephra tops, two standard dev iations, are marked with bold (HL8, HL1 7 and HL29). See discussion about confidence lev els in table A1 :6. The C1 4-age is interpolated by Rolf Zale (unpublished).

Samples Depth Age A B C D E Tot. sum. A B C D E Tot. HL1- cm 14C BP konc. HL30 no. no. no. no. no. no. no. dry no. dry no. dry no. dry no. dry no./g dry mass 1 0-1 -37 3 3 0 0 0 6 337 1 337 1 0 0 0 67 42 2 1 -2 -1 7 1 1 0 0 0 2 1 1 1 7 1 1 1 7 0 0 0 2233 3 2-3 0 1 6 2 0 1 0 1 9 22987 287 3 0 1 437 0 27 297 4 3-4 1 9 8 4 1 0 0 1 3 1 1 1 7 9 5590 1 397 0 0 1 81 66 5 4-5 37 7 5 1 0 0 1 3 7 994 57 1 0 1 1 42 0 0 1 4846 6 5-6 52 9 3 0 0 0 1 2 1 1 7 7 6 3925 0 0 0 1 57 02 7 6-7 7 2 26 3 0 0 0 29 31 1 34 3592 0 0 0 347 26 8 7-8 91 31 8 1 0 0 40 63197 16309 2039 0 0 81544 9 8-9 1 09 23 3 0 0 0 26 24669 321 8 0 0 0 27 887 1 0 9-1 0 1 27 31 7 4 0 0 42 31 1 36 7 031 401 8 0 0 421 85 1 1 1 0-1 1 1 37 6 1 4 1 0 1 2 8827 1 47 1 5885 1 47 1 0 1 7 654 1 2 1 1 -1 2 1 55 0 0 1 0 0 1 0 0 1 394 0 0 1 394 1 3 1 2-1 3 1 7 3 1 2 6 1 0 0 1 9 1 6063 8031 1 339 0 0 25433 1 4 1 3-1 4 1 91 1 0 0 0 0 1 1 1 25 0 0 0 0 1 1 25 1 5 1 4-1 5 209 6 2 0 0 0 8 1 0434 347 8 0 0 0 1 391 2 1 6 1 5-1 6 228 43 4 0 0 0 47 7 01 92 6529 0 0 0 7 67 21 17 16-17 246 32 7 7 1 1 48 72976 15963 15963 2280 2280 109463 1 8 1 7 -1 8 264 32 4 0 0 0 36 441 94 5524 0 0 0 497 1 8 1 9 1 8-1 9 282 49 3 0 0 0 52 681 27 41 7 1 0 0 0 7 2298 20 1 9-20 301 31 2 2 0 0 35 3951 3 2549 2549 0 0 4461 2 21 20-21 31 9 1 1 7 1 0 0 1 9 1 501 0 9552 1 365 0 0 25926 22 21 -22 338 7 0 2 0 0 9 1 2885 0 3681 0 0 1 6567 23 22-23 355 1 0 2 0 0 0 1 2 28204 5641 0 0 0 33845 24 23-24 37 3 7 3 2 0 0 1 2 8221 3523 2349 0 0 1 4093 25 24-25 389 9 2 1 0 0 1 2 1 2593 27 99 1 399 0 0 1 67 91 26 25-26 41 0 2 1 0 0 0 3 2250 1 1 25 0 0 0 337 4 27 26-27 427 8 4 1 0 0 1 3 1 31 1 2 6556 0 0 0 21 306 28 27 -28 448 7 7 1 0 0 0 1 88 1 1 3462 1 47 35 0 0 1 47 4 1 2967 0 29 28-29 467 123 5 0 0 0 128 217900 8858 0 0 0 226758 30 29-30 486 7 1 7 1 0 0 7 9 1 04684 1 0321 0 0 0 1 1 6480

82 Table A1 :4. Standard dev iation, Midge Lake.

Because there were v ery few samples from Midge Lake, the statistics is not rigorous enough to statistically arriv e at a confidence lev el for possible tephras abov e two standard dev iations. Ev en if the samples were div ided into smaller part, with just one top, it was not possible to arriv e at a result that was statistically confident (see table below). Only if one standard dev iation is used, two of the tops are confident, and was therefore used for subsampling for chemical analy sis (column 1 . Total -see below). The top which is at the largest depth, ML7 , is still not outside of the non-confident interv al. Howev er, sample ML7 was v ery small, about one tenth of the weight of the other samples (see Supplementary material on CD) and, hence, there are more analy tical problems and uncertainties with this sample than with the other samples. If only two more grains had been observ ed in sample ML7 (see table A1 :1 ), the lev el of this top would be abov e the non-confident interv al for one standard dev iation. Also, in Midge Lake there were many tephra lay ers. Two other groups of researchers had observ ed a tephra lay er at the same depth as ML7 , i.e. at a depth of 7 cm, in two other cores, and it is therefore of extra importance to try to find out if this is a tephra.

Legend: Std = one standard dev iation (68%). 2*Std = two standard dev iations (95%). Av erage = the mean for the samples analy sed in that column. Std + Av g is the minimum lev el for hav ing statistical confidence that there is a top, a possible tephra lay er. Column 1 = One standard dev iation, samples 1 -1 0. Column 2 = Two standard dev iations, samples 1 -1 0. Column 3 = Two standard dev iations, calculated only for samples 1 -7 . Column 4 = Two standard dev iations, calculated only for samples 4-6. Column 5 = Two standard dev iations, calculated only for samples 4-7 .

1 . Total 2. Total 3. S:1 -7 4. S:4-6 5. S:4-7 Std 1 1 4031 2*Std 228062 2*Std 27 2251 2*Std 3037 32 2*Std 31 057 8 Av erage 237 939 Av erage 237 939 Av erage 237 043 Av erage 1 40050 Av erage 1 87 7 1 9 Std + Av g 351 97 0 Std + Av g 466001 Std + Av g 509294 Std + Av g 4437 82 Std + Av g 498298

Table A1 :5. Standard dev iation, Lake Boeckella.

With only one standard dev iation, many tops were significantly ov er the mean (column 1 . Total, below). With two standard dev iations, only samples close to 20 cm (LB1 0-LB20) and at 59-60 cm (LB60) are significantly abov e the mean (column 2. Total). Howev er, samples LB88-LB89 are also significantly abov e the mean, if the v ery wide and high top at LB20 and all the more shallow samples from this lake are excluded (column 3, i.e. samples LB1 -LB20 hav e been taken away ), and therefore they are also interpreted as a tephra horizon. Chemical analy ses hav e been conducted on grains from the higher of the two tops, LB88.

Legend: Std = one standard dev iation (68%). 2*Std = two standard dev iations (95%). Av erage = the mean for the samples analy sed in that column. Std + Av g is the minimum lev el for hav ing statistical confidence that there is a top, a possible tephra lay er. Column 1 = One standard dev iation, calculated for all 89 samples. Column 2 = Two standard dev iations, calculated for all 89 samples. Column 3 = Two standard dev iations, calculated for samples 21 -89.

1 . Total 2. Total 3. S:21 -89 Std 396535 2*Std 7 93069 2*Std 61 3635 Av erage 7 1 91 58 Av erage 7 1 91 58 Av erage 600624 Std + Av g 1 1 1 5692 Std + Av g 1 51 2227 Std + Av g 1 21 4260

83 Table A1 :6. Standard dev iation, Hidden Lake.

After hav ing analy sed the first 27 samples for Hidden Lake, and calculated the statistical confidence lev el for two standard dev iation. Samples H8 and H1 7 showed a confidence lev el for being a tephra lay er. After hav ing analy sed samples 28-30 for v olcanogenic grain concentration, the confidence lev el rose to a much higher number, and the former supposed tephra horizons were not confident any longer. Now only sample HL29 was confident to more than 95%. For the chemical analy sis, for v erify ing if the top was a tephra, column 3 (2*S:26-27 ) was used for the upper samples and column 4 was used for sample HL29.

Legend: Std = one standard dev iation (68%). 2*Std = two standard dev iations (95%). Av erage = the mean for the samples analy sed in that column. Std + Av g is the minimum lev el for hav ing statistical confidence that there is a top, a possible tephra lay er. Column 1 = One standard dev iation, calculated for all 30 samples. Column 2 = One standard dev iations, calculated for samples 1 -27 . Column 3 = Two standard dev iations, calculated for samples 1 -27 . Column 4 = Two standard dev iations, calculated for all 30 samples.

Total S:26-27 2*S:26-27 Total Std 4837 9 Std-26-27 2661 2 2*Std-26- 53223 2*Std 967 60 27 Av erage 42949 Av erage 30206 Av erage 30206 Av erage 42949 Std + Av g 91 329 Std + Av g 5681 8 Std + Av g 83429 Std + Av g 1 397 09

Table A1 :7 . Percentage analy sis. Total number of all grains in each grain size class in all samples, as percentage of total grains. E.g, in Midge Lake 88.5% of all grains are between 21 and 40 µm

Size class 21 -40/All 41 -60/All 61 -80/All 81 -1 00/All 1 00+/All Midge L. 0.885 0.086 0.02 0.007 0.002 Lake B. 0.87 2 0.1 02 0.01 9 0.005 0.002 Hidden L. 0.829 0.1 27 0.035 0.004 0.003

Appendix 2. Subsample description for WDS, LA-ICP-MS and EDS analysis

Volcanogenic mineral grains and glass shards were subsampled for chemical analysis with a micropipette, from drops of water. Grains larger than c. 200 µm often were impossible to sample, as they got stuck in the hole of the micropipette.

A total of 494 mineral grains were subsampled for WDS/LA-ICP-MS, whereof 90 were c. 30- 40 ìm. Very few grains close to 20 ìm were sampled. It was hypothesized that between 100 and 300 grains could disappear or be difficult to analyse, and that there would still be a statistically valid number of grains for further analysis. But, during the gluing and polishing process many grains disappeared. WDS-analysis often gave a total mass percentage value of all elements that was too low and could not be used, even though it could be seen that the measured grain probably was not a shard. The latter result is because the WDS measured a lot of epoxy around the grains. A total less than 95% is usually too low, but those >60% are retained in table A2:1, below. (Full data is in Supplementary material, on CD.)

In the area of sample ML5, in mount 3, there was first much glue and the mount had to be repolished. Then, many grains were visible totally within the epoxy and could not be analysed. After the third polishing, there were very few grains left. Also, in mount 3 there

84 were many wide strings with air bubbles, which made all analyses difficult or impossible to conduct with LA-ICP-MS.

All mounts were polished just a little, to avoid grains from popping out. However, this made it difficult to analyse many grains with the WDS, as the visible surface area of the grains was too small.

Only those few grains that could possible be shards were analysed with LA-ICP-MS. But, even the numbers of these shrunk, as many grains popped out during the analysis and those from mount 3 were often impossible to identify after moving the mount from the WDS to the LA-ICP-MS.

Table A2:1 . Numbers of subsampled and analy sed grains. The column “Numbers of analy sed grains >60% total”, is all mineral grains of e.g. quartz or feldspar, or grains that may be shards, with a total of more than 60%. That is 237 grains, but 36 grain of these hav e total v alues between 60 and 90%, and 1 4 grains hav e totals between 90 and 95%. So, if these grains are subtracted, the numbers of “v alid” grains drops down to 201 or possible 1 87 grains. In the WDS-column, the first v alue is all grains except quartz-grains, and the second number is quartz-grains. After subtracting away the grains with low totals, from 1 1 5, we end up with 88 or 80 non-quartz grains left.

Sample Grain size (ìm) Numbers of analy sed Analy sis label grains >60% total and mount (M1 -M3) 20-40 40-80 >80 Total WDS LA-ICP-MS

ML1 8 41 9 58 1 9+3 3 O and P (M2)

ML5 1 3 30 6 49 3+0 0 R and S (M3)

ML7 1 4 32 1 3 59 20+8 0 T, U & V (M3)

LB1 0 1 0 32 6 48 5+22 3 I and J (M2)

LB1 8 4 30 1 0 44 7 +23 1 K and L (M2)

LB60 4 35 1 1 50 9+1 6 0 M and N (M2)

LB88 2 25 21 48 1 9+22 0 A and B (M1 )

HL8 1 1 35 6 52 1 3+1 3 1 C and D (M1 )

HL1 7 1 4 22 9 45 8+5 0 E and F (M1 )

HL29 1 0 22 9 41 1 2+1 0 1 G and H (M1 )

Sum: 90 304 1 00 494 1 1 5+1 22 9

Table A2:2. Numbers of subsampled and analy sed shards with EDS. Of the 1 32 grains, it was observ ed at once by the EDS that 43 grains were not shards and these were not analy sed. 89 grains were analy sed, but only 64 of these 89 grains were shards. Grains in the column EDS are all shards. Full data set in Supplementary material on CD. Sample Grain size (ìm) Numbers of shards Analy sis label

20-40 40-80 >80 Total EDS LA-ICP

ML7 5 30 1 0 45 30 n..a. MM48-MM89

LB88 3 1 5 23 41 22 n..a. MM1 -MM26

HL29 1 7 24 5 46 1 2 n..a. MM27 -MM47

Sum: 25 69 38 1 32 64 n..a.

85 Detailed description on how to mount grains for chemical analysis

For EDS analysis grains are not glued with epoxy, but only covered by carbon. It is just to fasten the grains on the special mount. Also, a special double adhesive tape with e.g. no S is needed, because otherwise the EDS will measure the tape instead of the grains. Also, if the grains touch eachother the reading may be disturbed by having more than one grain which give of X-rays at the same time.

Subsampling and procedure for chemical analysis, for making an epoxy mount for WDS or LA-ICP-MS (other methods are described in Kuehn and Froese 2010). 1. Cut a CD (or something else which is perfectly flat), so that the pieces are bigger than plastic rings or other mounting material used. Otherwise the epoxy may leak out, when making mounts for LA-ICP-MS or WDS. 2. Place the plastic ring (or similar, which is for marking the place where to make the epoxy mold for the mount) on the CD and draw an inner circle of the ring directly on the cd. 3. Place (transparent) sticky tape over the drawn circle, on the CD. (OBS! Flat!) Draw a chord over one part of the circle to mark the top of the sample. 4. All grains must now be placed within the circle. 5. Cut the sticky tape cover in rows (or small circular areas), but with one short side of the cut cover still clinging to the rest of the cover, so that you can open up one small part of the cover at a time, and afterwards put it back for diminishing the risk of contamination. Only use small openings on the sticky tape, for placing the grains. Otherwise the samples may be easily contaminated. However, it is not good to use too thin rows when working with a micropipette, as the grains are so small and can not bee seen when they are deposited on the mount. If using too thin rows, because of surface tension, the drop of water transferring the grains (with the micropipette), may stick to any surface outside of the sticky tape area. 6. Place grains in rows/application areas, with the first row starting a little bit down as a marker/starter row. Also, i.e. some grains may be put as markers in different places in the rows. Small markers of different material may also be used (e.g. small pieces of bristles from a new tooth brush). 7. Make a sketch of the entire mount. 8. Take a subsample from your sample to analyse. One single drop with a pipette is usually enough. Fill the subsample holder (usually a test tube) with water. Stir and decantate (use the pipette to decantate) a few times, so that all smaller grains (clay, small silt) disappear. Put drops of water from the stirred subsample on a microscope glass on a polarizing microscope. 9. Pick the grains, put them in the open row/application area. Be careful not to scratch the tape - just place the grains. The grains will stay on the tape during mounting. 10. Take the unsticky (uplifted) part of the tape cover and gently push the grains slightly into the sticky tape, after finishing a row/application area. Otherwise the grains may fall of during transport and preparation. 11. Place the plastic ring at the sample, where you earlier have drawn the inner circle. Draw same markings, on the outside of the ring, so that you will know what is up in your sample. 12. Then cover the subsample with epoxy, then take away tape, then polish, then analyse. Remember that the subsample now is mirror made, because you turned your mount upside down. (The present author did not make any epoxy mounts, and therefore the procedure of making epoxy mounts in not described here.)

86 Appendix 3. Grouping of WDS-analysis-data in shards/minerals

To find out what is a shard or not, a simple mathematical equation was constructed. The following formula of weight percentages of oxides of different major elements, is used to help classify grains in shards or minerals: (Al+Si)/(Fe+Ti+Mn+Mg)

This formula is constructed so that elements which are not common to feldspars are grouped together and will change the ratio (i.e., excluding K, Na, Ca), and it also takes into account if there is some atypical ratio with the most common major elements Si and Al. (A formula with only Si in the numerator gave a less consistent result.)

A shortcoming of the formula shows up if there is a very high abundance of some of the elements in the denominator, or a high abundance of only one of the feldspar “elements” K, Na or Ca, or if the abundance of Al is very high. In such cases a grain which is not a shard, may be given a low quotient and, hence, be sorted together with shards. Therefore, all supposed shards have to be classified separately, if necessary, for the correlations between different samples.

Grains with >60% total weight percent are sorted in grains with: a) Many elements that may be shards (table A3:1). A low quotient value indicate a shard, while a high value indicate a mineral of mainly feldspar affinity. b) Grains with very low abundance of the elements in the denominator, which are typical feldspars. (Table A3:2.) c) Silica rich grains, which are all regarded as quartz grains. (Table A3:3.) d) “Contaminating” grains, that just happened to be drawn up with the micropipette together with the other grains. (Table A3:4.) e) Grains with high Fe-Mg-content and very low K-Na-Ca-content, which are not shards. (Table A3:5).

Table A3:1 . Shards and minerals (starts on next page).

Grains are sorted with possible shards display ing lower v alues, according to the formula of weight percentages of oxides of different major elements. Numbers in left column is the same as those from the current research.

Twelv e samples from Appendix 5, whereof ten are from the research area (table A5:2) and two from other areas (table A5:3) (those with text in the left column), and four different feldspars (see text), hav e been added to the table, to make it easier to compare the current research with other published data. For the four feldspars, a v alue of 0.05% of Mg has been added. Otherwise the v alues of these will be ERR (it is not possible to div ide by zero).

Of the grains with lowest v alues, many of the c. 1 1 lowest may be minerals, e.g. grains 1 1 7 /LB1 8 and 29/ML1 appear to be py roxenes.

Only nine grains were possible to analy se with LA-ICP-MS. These are shadowed in the table (and hav e been labeled LA before the number, during later analy tical work). Except for the nine shadowed grains, no other grains which possible could be shards, could be analy sed with LA-ICP-MS. The other possible shards popped, where on mount 3, or - in a few cases - could not be identified after hav ing been mov ed from the WDS.

Of the grains analy sed by LA-ICP-MS, grain no. 97 in the lower half of the table is probably a feldspar. No. 1 1 0 and 1 35 are Fe-minerals. No. 1 22 and 1 31 display a high Na-content, and, hence, may be feldspars with an appearance of a shard. More safe is to say that grain no. 1 33 is a shard, and grain no. 1 33 is also close to a shard from Japan. The limit for “feldspar” are grains with higher v alues (further down in the table) than those shadowed, i.e. most grains with a higher v alue than grain 1 33. “Feldspars” may also include those with v ery high sodium-content higher up in the table.

87 Table A3:1

88 Table A3:1 (cont.)

Table A3:2. Grains which hav e v ery low or no abundance of Fe, Ti, Mn and Mg, and therefore hav e a v ery high v alue in the table. These are ty pical feldspars.

89 Table A3:3. Grains rich in silica, mainly pure quartz, from 80% and more (those with a lower percentage than 80%, also hav e a low total and, hence, the total Si-content is more than 80%). Grains sorted after samples.

90 Table A3:3. (cont.)

91 Table A3:4.

Grains with v ery low Si-content, that were just drawn up together with the other grains during micropipetting. But, ev en the iron and titanium rich grains in the table may be v olcanogenic mineral grains.

Grains 1 65-1 66 and 1 7 9 from ML7 (Midge Lake) are completely black grains, magnetite or hematite. Grains 1 1 4 from HL1 7 and 1 00 from HL8 (Hidden Lake) are probably contaminants, because all is CaO. Grain 1 03 from HL1 7 (Hidden Lake) is a titanium oxide mineral (rutile).

Table A3:5.

Grains with v ery high Mg- or Fe-Mg-content, and low Na, K and Ca, and thus probably are serpentinites (1 1 7 , 207 , 208), and, high Ca and Mg, and low Na and K, which may be hornblende (29, 1 1 8, 1 23, 1 81 ), and, one grain with v ery many elements but low Si, which appears to be some kind of titanium-bearing biotite (7 1 , but - the appearance of the grain was not like biotite) (compare to mineral in Yav uz et al. 2002). But, ev en these grains may be v olcanogenic mineral grains.

Appendix 4. Instruments/methods used in tephrochronology for chemical and other analysis

Methods for chemical analyses

Many methods for chemical analysis of volcanic grains have been used by different researchers. This has made comparisons of different results difficult. Some of these methods are not in use any longer, and EPMA followed by LA-ICP-MS is becoming the more dominant method. Many methods are mentioned by Pearce et al. (1997). Lowe (2011) describes differences between some methods, to help set up a scheme of analysis.

An easy to understand description of EPMA methods (in general, WDS and EDS), is posted on Science Education Resource Center at Carleton College (June 2012) and an instruction for LA-ICP-MS is posted on the Vanderbilt University website (June 2012). Also, both EPMA, laser ablation, which is a simple way to turn samples into plasma, and the basic method of determining different elements, i.e. ICP-MS, are shortly described on the English Wikipedia (2012).

In table A4:1 methods of chemical analysis are tabulated, and in table A4:2 non-chemical methods are tabulated. In some cases the methods are shortly commented upon.

92 Table A4:1 . Methods of chemical element analy sis.

1 . AA = Atomic absorption (e.g. Sarna-Wojcicki 2002). 2. AAS = Atomic absorption spectrometry . 3. CPAA = Charged particle activ ation analy sis. 4. DNAA = Delay ed neutron activ ation analy sis. 5. EPMA/EMP/EMA = Electron microprobe analy sis, or, electron probe microanaly sis, in a SEM (e.g Pillans et al. 2005, Knott et al. 2007 ) with EDS = Energy dispersiv e spectrometry = EDX/EDAX/EDXRA = Energy dispersiv e analy sis of X-ray s (e.g. Hodgson et al. 1 998, Hillenbrand et al. 2008) or WDS/WDXRA = Wav elength dispersiv e spectrometry /wav elength dispersiv e X-ray analy sis (e.g. Hodgson et al. 1 998). 6. GDMS = Glow discharge mass spectrometry . The method may differ with INAA as much as 200% for some elements (Pearce et al. 1 997 ). 7 . GFAAS = Graphite furnace atomic absorption spectroscopy . 8. HeAA = Helium ion activ ation analy sis. 9. HIAA = Heav y ion activ ation analy sis.

Methods 1 0-1 9 are all inductiv ely coupled plasma spectrometry /spectroscopy .

1 0. AES-ICP = Auger electron spectroscopy - with inductiv ely coupled plasma spectrometry /spectroscopy (e.g. Björck and Zale 1 996a). 1 1 . ICP-ES/ICP-OES = Optical emission spectroscopy (e.g. Hunt and Hill 1 993, Pallàs et al. 2001 , Jochum et al. 201 1 ). 1 2. ID-ICP-MS = Isotope dilution inductiv ely coupled plasma mass spectrometry (e.g. Jochum et al. 201 1 ). 1 3. ICP-MS = Inductiv ely coupled plasma mass spectrometry (e.g. Hunt and Hill 1 993, Pallàs et al. 2001 ). Older analy ses may differ with up to 400%, between different ICP-MS-laboratories (Pearce et al. 1 997 ) 1 4. ICP-AES = Inductiv ely coupled plasma atomic emission spectrometry (e.g. Knott 2007 ). 1 5. LA-ICP-MS = Laser ablation inductiv ely coupled plasma mass spectrometry (e.g. Lowe 2008, 201 1 ). A few laboratories and methods are mentioned by Jochum et al. (201 1 ) and LA-ICP-MS is described. Older LA-ICP-MS- analy ses differ up to 50% compared to INAA (Pearce et al. 1 997 ) 1 6. LP-MS = Laser probe mass spectrometry . 1 7 . MC-ICP-MS = Multi-collector inductiv ely coupled plasma mass spectrometry (e.g. Jochum et al. 201 1 ). 1 8. S(N)-ICP-MS = Solution (nebulisation) inductiv ely coupled plasma mass spectrometry (e.g. Li et al. 201 0). A large sample size is needed and the method is often used for bulk analy ses (Pearce et al. 2007 , 201 1 ). The method is problematic if e.g. zircon occur (Li et al. 201 0). Process for solution described by Knott et al. (2007 ).

1 9. SN-ICP-MS on a melt of alkali salts, e.g. LiBO2 (Li et al. 201 0, pers. comm. Rolf Zale 201 1 ).

20. ID-SSMS = Isotope dilution spark source mass spectrometry . 21 . ID-TIMS = Isotope dilution TI mass spectrometry (Jochum et al. 201 1 ). 22. IDMS = Isotope dilution mass spectrometry (Weav er et al. 1 97 9, Meija and Mester 2008). 23. LA-SSMS = Laser ablation spark source mass spectrometry . 24. IMA = Ion microprobe analy sis (Hillenbrand et al. 2008). 25. IMMA = Ion microprobe mass analy sis. 26. INAA/INA/NAA = Instrumental neutron activ ation analy sis. A nuclear reactor is needed for this method. A large sample size is needed and the method is often used for bulk analy ses (Pearce et al. 2007 , 201 1 ). And, one need to be cautious to compare INAA with S-ICP-MS as the result may be different (e.g. Pallàs et al. 2001 , Knott et al. 2007 ). 27 . IPAA = Instrumental photon activ ation analy sis. 28. NMP = Nuclear microprobe. 29. NTM = Nuclear track methods. 30. PIXE = Proton/particle induced X-ray emission and EAI - Elemental Analy sis (e.g. Jochum et al. 201 1 ). 31 . POL = Polarography . 32. RAD = Radiography . 33. SIMS = secondary ionization/ion mass spectrometry = ion microprobe analy sis (e.g. Pearce et al. 2007 , Lowe 2008, Lowe 201 1 ). This method is more expensiv e and slower than e.g. LA-ICP-MS (Pearce et al. 2007 , 201 1 , Lowe 201 1 ). 34. SSMS = Spark source mass spectrometry (e.g. Jochum et al. 201 1 ).

93 35. SXRF = Sy nchrotron X-ray fluorescence. 36. TAGS = Thermal neutron capture gamma ray spectrometry . 37 . XRF = X-ray fluorescence (e.g. Pallàs et al. 2001 , Ky lander et al. 201 1 ). XRF can only analy se a few trace elements (Li et al. 201 0).

Non-chemical methods to identify tephras

Table A4:2. Methods of non-chemical analy sis

1 . Back scattered light = Light sent through holes in glacier ice (Dunbar and Kurbatov 201 1 ). 2. Magnetic susceptibility (Björck et al. 1 991 a, 1 993), but not alway s a good indicator of tephras (Hodgson et al. 1 998). There are different kinds of magnetic susceptibility methods: a) Mass specific magnetic susceptibility . b) HIRM = high (or sometimes, “hard”) isothermal remanent magnetization, or, mass specific high induced remanent magnetization (indicator of hematite and goethite) (Zale 1 993, Liu et al. 2007 ). c) SIRM = saturation remanent magnetization. 3. PSA = Silt particles that scintillate under cross-polarized light (Py ne-O´Donnell 201 0). 4. SEM surface microtextures (e.g. Katoh et al. 2000, Pallàs et al. 2001 , Lowe 201 1 ). Reworking may be easier to detect with SEM than with pure optical analy sis. 5. X-ray photos of sediment cores (Zale and Karlén 1 989, Zale 1 993).

Appendix 5. Examples of earlier published geochemistry data from tephras, mainly from the research area

Deception Island, samples and age

There are multitudes of Deception Island data concerning eruptions and geochemistry. However, it is difficult to tie eruptions to samples. Some samples can be inferred to special eruptions, but most are just in the general “ball park”. Below is a list of samples and formations which have been correlated, by comparing literature data.

94 Table A5:1 : Sections with dated samples from Deception Island. Data from Aristarain and Delmas (1 998), Pallàs et al. (2001 ), Smellie (2001 , 2002a, 2002c), Smellie and Fretzdorff (2002), Smellie and Millar (2002) and Kurbatov et al. (2006).

The following formations, mentioned by Smellie at al. (1 992), hav e not been stratigraphically dated or analy sed chemically : Late post-caldera tuff cones Post-caldera Strombolian fissure v ents Early post-caldera tuff cones Pre-caldera v olcanic rocks

The following formations hav e been stratigraphically dated, but hav e not been analy sed chemically (Smellie 2001 , 2002a, 2002c, Smellie and Millar 2002): Mt Pound upper slopes, 1 906-1 91 2, 1 931 , 1 955 Mt Pound, 1 830, 1 927 Crimson Hill (Pendulum Cov e) 1 800, 1 828 Sealers harbour 1 7 90-1 800

Sample/name Age

POST-CALDERA

Telefon Bay cone cluster 1 967 -1 97 0 (and one pre-1 9th century that is not sampled/reported: “Sealers harbour”)

Mount Kirkwood Member 1 838-39, 1 842, 1 969

Kroner Lake cone cluster 1 830, 1 908, mainly 1 9th century

Unknown, in ice dome 1 87 1 (tabulated by Kurbatov et al. 2006)

Vapor Col cone cluster pre-1 829

Cross Hill cone cluster pre-1 829

Crater Lake cone cluster likely 1 8th century , probably pre-1 829

Collins Point cone cluster probably pre-1 8th century

Unknown, in glacier 1 641

Baily Head Formation probably sev eral thousand

Kendall Terrace Member probably sev eral thousand and at least in part older than Baily Head

PRE-CALDERA

Outer Coast Tuff Not more than c. 36-1 00 ka

Basaltic Shield Not more than c. 36-1 00 ka

Fumarole Bay Not more than c. 36-1 00 ka

Published geochemistry analyses of volcanic eruptives

Geochemical data from lakes, glaciers, marine sediments, Deception Island and other volcanoes in mainly the Antarctic area, are tabulated below. Each list of raw data is documented with information about methods etc., and then shortly commented on. These data are also used to show which elements may be of most importance for tephrochronology correlations. The analytical results from table A5:2 and table A5:3 are in Supplementary material on CD.

95 Table A5:2. Antarctic Peninsula research area. Tephras from marine, lake and glacial env ironments, and from v olcanoes mainly in the research area. Earlier published results. (DI = Deception Island.)

1 -3. Midge Lake and Sombre Lake (South Orkney Islands). Method: EPMA with EDS and WDS, on indiv idual tephra glass shards, basaltic and acidic, and at least 1 5 shards/tephra. High percentage of mineral matter in Sombre Lake tephra, only one grain analy sed and not tabulated here (Hodgson et al. 1 998). Ti, Fe, Mg, Ca and K ratio v aries more than 20% (e.g. a 1 0% and a 1 2% absolute difference in weight ratio is 20% different in percentages). If Sombre Lake (South Orkney Island) is taken into account, Na is also different. Preparations were made to preclude Na-loss in this research.

4-9. Liv ingston Island, in glaciers on Hurd Peninsula, which is the place closest to DI v in the most common wind direction (compared to tephras on DI) (Pallàs et al. 2001 ) . These are bulk samples. Therefore, we can not use the data just off the shelf, but we can use it to find possible elements for good correlations. Methods: XRF, ICP-ES, ICP-MS, INAA. Only Mg, Ca, K and P hav e large different ratios (more than 20% percentage - see description/example abov e). All minor elements hav e large different ratios in more than one sample (if it is just in a single sample, it may be “by chance”) except Zn, Ga, Sr, Eu, U and Ta (the last two only present in three samples). Mg, Ca, K, P hav e large differences on Hurd Peninsula (Pallàs et al. 2001 ). Many samples believ ed to be from the same eruption.

1 0-1 1 . There is no published chemical data from Hidden Lake, James Ross Island, but the recorded tephras are correlated with other lakes (Björck et al. 1 991 a). One tephra lay er is recorded as 250 y ears old in Hidden Lake, but the most powerful eruption is dated to 350 y ears by ice core chronology and is the only v isible eruption recorded in the glacier on James Ross Island. This eruption is correlated with a tephra in the South Pole Station ice core (Aristarain and Delmas 1 998, Palais et el. 1 989). Method: EDAX/EDS = EPMA. Bulk glass shard sample (as described by Palais et al. 1 990).

1 2. South Pole ice core sample. Sample believ ed to be from the DI 1 91 2 eruption (sample 8). Method: EDAX/EDS (Palais et al. 1 989).

1 3-1 6. King George Island. After chemical analy ses the shards were div ided into basaltic and silicic glass, and compared within and between eachother, and believ ed to be mixed from different v olcanoes. There was v ery little v ariation within the groups (see table), but large between the groups. About 1 0% of the basaltic grains hav e chemical compositions that does not correlate well with any known source v olcano (Lee et al. 2007 ). The other tephras are believ ed to be from DI, ev en though the SC-v alues are low - the latter is interpreted as contamination/mixing with ashes from other v olcanoes (Lee et al. 2007 ). Method: WDS.

1 7 -1 8. Two tephras in the Epica-Dome C, interpreted to be from DI, dated to 7 3.7 and 1 53.2 ka respectiv ely . But the grain size was so small that only the less precise EDS could be used on unpolished grains. Grain size <1 0 µm, bulk analy sis. Glass shard particles identified. Methods: EPMA, EDS, WDS. Preparations were made to preclude Na-loss. (Narcisi et al. 2005.)

1 9-28. Bransfield Basin. Marine sediments, basaltic to basaltic andesitic glass shards (brownish to black in colour), which plot in the geochemical field of DI except one tephra horizon (“No. 1 ") which consist entirely of colourless silica rich andesite (intermediate magma). This last tephra horizon is y ounger than a few hundred y ears (probably 60-230 y ears) and it was suggested that this horizon may be could be from the submarine Hook Ridge (but the composition of Hook Ridge is not known). Also, a bimodal horizon (I263) had one rhy olitic component (7 0.69%

SiO2). 21 -23 are outside DI chemical character. (But, the last eruptions of DI are andesitic.) Grain size >63 µm, av erage 1 00 µm. Methods: EPMA-WDS, also compared with XRF on DI lav as. (Good diagrams and tables.) Small beam size to minimise Na-loss, but Na-loss is speculated for differences in Na-ratio compared to DI “in situ” samples. P v ary v ery much within horizon-samples and, hence, one can speculate that there was some problem with contamination or with the analy ses (Fretzdorff and Smellie 2002). Intermediate 52-63% Andesite (v olcanic), diorite.

29-30. Tephra believ ed to be a bimodal eruption on DI, i.e. the tephras are display ing a thorough mix of brown basaltic and clear siliceous glass and no or few shards with an intermediate chemical composition (Moreton and Smellie 1 998).

96 31 -57 . DI. Volcanic bombs, lav as and pumice hav e been analy sed for different elements. All analy ses were on bulk samples. Method: Bulk XRF. (Fretzdorff and Smellie 2002, Smellie 2002a, Smellie and Millar 2002). There is much scatter in the data (more than 20% difference between different ratios) in all elements except Si and Al. (Mn, Zn and Ga was close to 20%.)

58-65. Samples that are not mentioned with the other DI samples. Considering the large v ariations in F, B, K and P in lav as from DI. Smellie et al. (1 992) speculated about open-sy stem fractionation and other means of mixing with “foreign” material.

66-7 2. More data from Deception, Penguin and Bridgeman islands were reported by Weav er et al. 1 97 9. Samples were not specified by Weav er et al. (1 97 9) to any special outcrop, and therefore all are tabulated together as highest and lowest v alues. Main method: XRF. IDMS = mass spectrometry isotope dilution, on: Ba, Ce, Nd, Sm, Eu, Gd, Dy , Er and Yb. (Values for Ba and Ce approximately the same for both methods, but one sample was 7 9 instead of 1 02 for Ba with this method.)

7 3-81 . More data and v olcanoes in Keller et al. (1 992). Bridgeman Island had activ e fumaroles in 1 821 and 1 850, but is believ ed to hav e had larger eruptions c. 60 ka ago ev en though it appear similar in outcrop as the much y ounger (ka) Baily Head Formation (former Neptunes Bellows Group) (Weav er et al. 1 97 9, Keller et al. 1 992, Smellie 2001 ). Sail Rock - unknown age (Keller et al. 1 992). Low Head on King George Island ca 24 Ma; Melv ille Peak on King George Island ca 300 ka; Penguin Island, probably activ e in historical time, a few hundred y ears ago (Weav er et al. 1 97 9, Keller et al. 1 9921 ). Methods: XRF, IDMS and ICP-MS. Sample 69. Ba-v alues and all higher elements from IDMS/ICP-MS. Lighter elements with XRF.

82. Lav a, bulk sample, mean of two (Fretzdorff and Smellie 2002).

83. Lav a, one single bulk sample (Smellie et al. 2006).

84-1 95. Data published by Kraus et al. 201 3 (in press).

Below: Other less precise analy ses from the research area, which are not tabulated.

Orheim 1 97 2 reported ratios of Na, Mg, Al, Si, P, K, Ca, Ti, two different Fe-oxides (but no Mn), from two v ents on DI but he did not report which method was used for the analy ses.

Many geochemical v alues hav e been published on shards from many lakes on By ers Peninsula, including Midge Lake which is a part of the current project. Howev er, these hav e been measured under not controlled analy tical conditions, and lakes close to eachother could not be correlated. The lack of correlation between lakes was referred to as “contamination” of the samples, and the data can not be used for much more than showing the presence of different elements (Björck and Zale 1 996a p. 46-47 and Björck and Zale 1 996b p. 62). The samples were analy sed with AES-ICP. Major elements: Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe. Minor/trace elements: Sc, V, Cr, Co, Ni, Cu, Zn, Sr, Y, Zr, Nb, Ba, Yb, W.

There is unpublished data from Lake Boeckella, with ICP-MS and SN-ICP-MS used with LiBO2-melt. ICP-MS detected more elements then the LiBO2-melt. Howev er, the methods of analy sis and collection of data were not v ery exact, so the data show more presence or absence of different elements than any ratios (pers. comm. Rolf Zale 201 1 ). The following major elements were present: Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe. The following minor/trace elements were present: Li, Be, Sc, V, Cr, Co, Ni, Cu, Zn, As, Rb, Sr, Y, Zr, Mo, Ag, Cd, Sn, Sb, Ba, La, Pb, Th, U, W. (Li, Be, Mo, As, Ag, Cd, Sn, Sb, W, Pb has been detected almost only in this study . But Ga, Nb, Cs, Hf, Ta, Ce, Nd, Sm, Eu, Tb, Yb, Lu were not detected, ev ent though these elements are used by many other researchers).

97 Place/sample Methods Comments/discussion Reference

1 . Midge Lake, 3-4 EPMA/WDS/ Acidic tephra. 1 3 grains. Fe2O3 (t). Hodgson et al. 1 998 cm EDS

2. Midge Lake, 8-9 EPMA/WDS/ Basaltic tephra. 1 5 grains. Fe2O3 (t). Hodgson et al. 1 998 cm EDS

3. Midge Lake, 21 - EPMA/WDS/ Basaltic tephra. 1 4 grains. Fe2O3 (t). Hodgson et al. 1 998 22 cm EDS

4. Liv ingston XRF, ICP-ES, Lowest data tabulated here. Interpreted asPallàs et al. 2001 Island, glacier, ICP-MS, TPH1 , 1 97 0 DI eruption. Four samples.

TPH1 , lowest INAA Fe2O3 (t).

5. Liv ingston Island, XRF, ICP-ES, Highest data tabulated here. Interpreted Pallàs et al. 2001 glacier, TPH1 , ICP-MS, as TPH1 , 1 97 0 DI eruption. Four samples. highest INAA Fe2O3 (t).

6. Liv ingston XRF, ICP-ES, Sample ES. Interpreted as TPH2, pre- Pallàs et al. 2001

Island, glacier, ICP-MS, 1 829 DI eruption, two samples. Fe2O3 (t). TPH2, ES INAA

7 . Liv ingston Island, XRF, ICP-ES, Sample JSA. Interpreted as TPH2, pre- Pallàs et al. 2001 glacier, TPH2, JSA ICP-MS, 1 829 DI eruption, two samples. Fe2O3 (t). INAA

8. Liv ingston XRF, ICP-ES, Lowest data tabulated here. Interpreted asPallàs et al. 2001

Island, glacier, ICP-MS, TPH3, ten samples. Fe2O3 (t). TPH3, lowest INAA

9. Liv ingston XRF, ICP-ES, Highest data tabulated here. Interpreted Pallàs et al. 2001

Island, glacier, ICP-MS, as TPH3, ten samples. Fe2O3 (t). TPH3, highest INAA

1 0. James Ross EDAX/EDS Interpreted as a 1 641 DI eruption (sample Aristarain and Delmas Island, glacier 6). FeO (t). 1 998, Palais et al. 1 989

1 1 . South Pole ice EDAX/EDS Interpreted as a 1 641 DI eruption (sample Aristarain and Delmas core sample 7 ). FeO (t). 1 998, Palais et al. 1 989

1 2. South Pole ice EDAX/EDS Stated to be from the DI 1 91 2 eruption Palais et al. 1 989 core sample (sample 8). FeO (t).

1 3. King George WDS on Lowest, basaltic population, from six Lee et al. 2007 Island basaltic and tephra horizons. FeO (t). silicic glass

1 4. King George WDS on Highest, basaltic population, from six Lee et al. 2007 Island basaltic and tephra horizons. FeO (t). silicic glass.

1 5. King George WDS on High-K rhy olitic population. Mean from Lee et al. 2007 Island basaltic and three horizons. FeO (t). silicic glass

1 6. King George WDS on Low-K silicic population. Mean from two Lee et al. 2007 Island basaltic and horizons. FeO (t). silicic glass

1 7 . EPICA- Dome C, EPMA, EDS, Sample 1 1 1 7 .1 . Too small grains for WDS, Narcisi et al. 2005 age 7 3.7 ka (WDS) ice core. FeO (t).

1 8. EPICA- Dome C, EPMA, EDS, Sample 1 868.3, ice core. Too small grains Narcisi et al. 2005 age 1 53.2 ka (WDS) for WDS. FeO (t).

98 1 9. Bransfield basin, XRF, EPMA- All these horizons believ ed to be from DI. Fretzdorff and Smellie lowest, 1 8 horizons- WDS Lowest data tabulated here. FeO (t). 2002 samples

20. Bransfield XRF, EPMA- All these horizons believ ed to be from DI. Fretzdorff and Smellie basin, highest, 1 8 WDS Highest data tabulated here. FeO (t). 2002 horizons-samples

21 . Bransfield basin, XRF, EPMA- Horizon correlated with TPH2, Liv ingston Fretzdorff and Smellie horizon No. 2, WDS Island (see abov e), and eruption 1 839- 2002 lowest, 6 horizons- 1 842 from DI (see below). L0west data samples tabulated here. FeO (t).

22. Bransfield XRF, EPMA- Horizon correlated with TPH2, Liv ingston Fretzdorff and Smellie basin, horizon No. WDS Island (see abov e), and eruption 1 839- 2002 2, highest, 6 1 842 from DI (see below). Highest data horizons-samples tabulated here. FeO (t).

23. Bransfield XRF, EPMA- Horizon correlated with DI (see below). Fretzdorff and Smellie basin, horizon No. WDS Lowest data tabulated here. FeO (t). 2002 3, lowest, 3 horizons-samples

24. Bransfield XRF, EPMA- Horizon correlated with DI (see below). Fretzdorff and Smellie basin, horizon No. WDS Highest data tabulated here. FeO (t). 2002 3, highest, 3 horizons-samples

25. Bransfield XRF, EPMA- Horizon correlated with TPH1 (see abov e) Fretzdorff and Smellie basin, horizon A, 1 2 WDS and the 1 97 0 eruption of DI (see below). 2002, Pallàs et al. 2001 shards Howev er, the correlation was not as good as for the horizon-sample No. 2 (= number 1 7 , in this table). FeO (t).

26. Bransfield XRF, EPMA- Horizon not from DI. L0west data Fretzdorff and Smellie basin, horizon No. WDS tabulated here. FeO (t). 2002 1 , lowest, 6 horizons-samples

27 . Bransfield XRF, EPMA- Horizon not from DI. Highest data Fretzdorff and Smellie basin, horizon No. WDS tabulated here. FeO (t). 2002 1 , highest, 6 horizons-samples

28. Bransfield XRF, EPMA- Acidic part of “bimodal” horizon believ ed Fretzdorff and Smellie basin, horizon I263, WDS to be from DI. FeO (t). 2002 7 shards

29. Scotia Sea, EPMA-WDS, Basic part of “bimodal” horizon believ ed Moreton and Smellie mean of 80 samples EDS to be from DI. FeO (t). 1 998

30. Scotia Sea, EPMA-WDS, Acidic part of “bimodal” horizon believ ed Moreton and Smellie mean of 45 samples EDS to be from DI. FeO (t). 1 998

31 . DI, Telefon Bay XRF Bulk sample, one sample, B.7 67 .1 , FeO (t)S. mellie et al. 1 992, 1 97 0 Fretzdorff and Smellie 2002, Smellie 2002a, Smellie and Millar 2002

32. DI, Telefon Bay XRF Bulk samples, four samples, lowest v alues,Smellie et al. 1 992,

1 967 -1 97 0, lowest Fe2O3 (t). Smellie 2002a, Smellie and Millar 2002

33. DI, Telefon Bay XRF Bulk samples, four samples, highest Smellie 2002a, Smellie

1 967 -1 97 0, highest v alues, Fe2O3 (t). and Millar 2002

99 34. DI, Telefon Bay XRF Bulk sample, one sample, FeO (t). Fretzdorff and Smellie 1 967 , sample 2002, Smellie and B.7 82.2 Millar 2002

35. DI, Telefon Bay XRF Bulk sample, one sample, FeO (t). Fretzdorff and Smellie 1 967 , sample 2002, Smellie and B.7 68.2(B) Millar 2002

36. DI, Mt XRF Bulk samples, four samples, lowest v alues,Smellie et al. 1 992,

Kirkwood, low FeO (t) and Fe2O3 (t). Fretzdorff and Smellie 2002, Smellie 2002a, Smellie and Millar 2002

37 . DI, Mt XRF Bulk samples, four samples, highest Smellie et al. 1 992,

Kirkwood, high v alues, FeO (t) and Fe2O3 (t). Fretzdorff and Smellie 2002, Smellie 2002a, Smellie and Millar 2002

38. DI, Kroner Lake XRF Bulk samples, mean of two samples, Fe2O3 Smellie et al. 1 992, (t). Smellie 2002a, Smellie and Millar 2002

39. DI, Vapor Col, XRF Bulk samples, three samples, lowest Smellie et al. 1 992, lowest v alues, Fe2O3 (t). Smellie 2002a, Smellie and Millar 2002

40. DI, Vapor Col, XRF Bulk samples, three samples, highest Smellie 2002a, Smellie highest v alues, Fe2O3 (t). and Millar 2002

41 . DI, Cross Hill, XRF Bulk samples, fiv e samples, lowest v alues, Smellie et al. 1 992, lowest Fe2O3 (t). Smellie 2002a, Smellie and Millar 2002

42. DI, Cross Hill, XRF Bulk samples, fiv e samples, highest v aluesS, mellie et al. 1 992, highest Fe2O3 (t). Smellie 2002a, Smellie and Millar 2002

43. DI, Crater Lake, XRF Bulk samples, four samples, lowest v alues,Smellie et al. 1 992, lowest Fe2O3 (t) and FeO (t). Fretzdorff and Smellie 2002, Smellie 2002a, Smellie and Millar 2002

44. DI, Crater Lake, XRF Bulk samples, four samples, highest Smellie et al. 1 992, highest v alues, Fe2O3 (t) and FeO (t). Fretzdorff and Smellie 2002, Smellie 2002a, Smellie and Millar 2002

45. DI, Collins XRF Bulk samples, three samples, lowest v aluesSmellie et al. 1 992,

Point, lowest Fe2O3 (t). Smellie 2002a, Smellie and Millar 2002

46. DI, Collins XRF Bulk samples, three samples, highest Smellie 2002a, Smellie

Point, highest v alues Fe2O3 (t). and Millar 2002

47 . DI, Baily Head, XRF Bulk samples, fiv e samples, lowest Fe2O3 Smellie et al. 1 992, lowest (t). Smellie 2002a, Smellie and Millar 2002

48. DI, Baily Head, XRF Bulk samples, fiv e samples, highest Fe2O3 Smellie et al. 1 992, highest (t). Smellie 2002a, Smellie and Millar 2002

49. DI, Kendall XRF Bulk samples, six samples, lowest, Fe2O3 Smellie et al. 1 992, Terrace, lowest (t). Smellie 2002a, Smellie and Millar 2002

100 50. DI, Kendall XRF Bulk samples, six samples, highest, Fe2O3 Smellie et al. 1 992, Terrace, highest (t). Smellie 2002a, Smellie and Millar 2002

51 . DI, Outer Coast XRF Bulk samples, mean of two samples (pre- Smellie 2002a, Smellie

Tuff, high SiO2 caldera), pumice, Fe2O3 (t). and Millar 2002

52. DI, Outer Coast XRF Bulk samples, twelv e samples (pre- Smellie 2002a, Smellie

Tuff, low SiO2, caldera), bomb, lowest v alues, Fe2O3 (t). and Millar 2002 lowest

53. DI, Outer Coast XRF Bulk samples, twelv e samples (pre- Smellie 2002a, Smellie

Tuff, low SiO2, caldera), bomb, highest v alues, Fe2O3 (t). and Millar 2002 highest

54. DI, Basaltic XRF Six bulk samples (pre-caldera), lowest Smellie et al. 1 992,

Shield, lowest v alues, Fe2O3 (t). Smellie 2002a, Smellie and Millar 2002

55. DI, Basaltic XRF Six bulk samples (pre-caldera), highest Smellie et al. 1 992,

Shield, highest v alues, Fe2O3 (t). Smellie 2002a, Smellie and Millar 2002

56. DI, Fumarole XRF Fiv e bulk samples, oldest (pre-caldera), Smellie et al. 1 992,

Bay , lowest lowest v alues, Fe2O3 (t). Smellie 2002a, Smellie and Millar 2002

57 . DI, Fumarole XRF Fiv e bulk samples, oldest (pre-caldera), Smellie 2002a, Smellie

Bay , highest highest v alues, Fe2O3 (t). and Millar 2002

58. DI, F and B, XRF Late post-caldera. Four bulk samples, Smellie et al. 1 992 lowest lowest v alues,

59. DI, F and B, XRF Late post-caldera. Four bulk samples, Smellie et al. 1 992 highest highest v alues. Fe not measured.

60. DI, F and B, XRF Post-caldera. Ten bulk samples, lowest Smellie et al. 1 992 lowest v alues. Fe not measured.

61 . DI, F and B, XRF Post-caldera. Ten bulk samples, highest Smellie et al. 1 992 highest v alues. Fe not measured.

62. DI, F and B, XRF Early post-caldera. Three bulk samples, Smellie et al. 1 992 lowest lowest v alues. Fe not measured.

63. DI, F and B, XRF Early post-caldera. Three bulk samples, Smellie et al. 1 992 highest highest v alues. Fe not measured.

64. DI, F and B, XRF Pre-caldera. Six bulk samples, lowest Smellie et al. 1 992 lowest v alues. Fe not measured.

65. DI, F and B, XRF Pre-caldera. Six bulk samples, highest Smellie et al. 1 992 highest v alues. Fe not measured.

66. DI, lowest XRF, IDMS Twelv e bulk samples but only six for Weav er et al. 1 97 9

IDMS. Lowest v alues. Fe2O3 (t)

67 . DI, highest XRF, IDMS Twelv e bulk samples but only six for Weav er et al. 1 97 9

IDMS. Highest v alues. Fe2O3 (t).

68. DI XRF One sample, rhy odacite Fe2O3 (t). Weav er et al. 1 97 9

69. Penguin Island, XRF, IDMS Six bulk samples but only two for IDMS. Weav er et al. 1 97 9 lowest Lowest v alues. Fe2O3 (t).

7 0. Penguin Island, XRF, IDMS Six bulk samples but only two for IDMS. Weav er et al. 1 97 9 highest Highest v alues. Fe2O3 (t).

101 7 1 . Bridgeman XRF, IDMS Four bulk samples but only two for IDMS. Weav er et al. 1 97 9

Island, lowest Lowest v alues. Fe2O3 (t).

7 2. Bridgeman XRF, IDMS Four bulk samples but only two IDMS. Weav er et al. 1 97 9

Island, highest Highest v alues. Fe2O3 (t).

7 3. DI, lowest XRF, IDMS, Twenty bulk samples but only fiv e for Keller et al. 1 992 ICP-MS IDMS/ICP-MS. Lowest v alues. FeO (t).

7 4. DI, highest XRF, IDMS, Twenty bulk samples but only fiv e for Keller et al. 1 992 ICP-MS IDMS/ICP-MS. Highest v alues. FeO (t).

7 5. Sail Rock XRF, IDMS, One bulk sample. FeO (t). Keller et al. 1 992 ICP-MS

7 6. Bridgeman XRF Mean of two bulk samples. FeO (t). Keller et al. 1 992 Island

7 7 . Low Head, King XRF, IDMS, One sample. FeO (t). Keller et al. 1 992 George Island ICP-MS

7 8. Melv ille Peak, XRF, IDMS, Four bulk samples but only two for Keller et al. 1 992 King George Island, ICP-MS IDMS/ICP-MS. Lowest v alues. FeO (t). lowest

7 9. Melv ille Peak, XRF, IDMS, Four bulk samples but only two for Keller et al. 1 992 King George Island, ICP-MS IDMS/ICP-MS. Highest v alues. FeO (t). highest

80. Penguin Island, XRF, IDMS, Fiv e bulk samples but only two for Keller et al. 1 992 lowest ICP-MS IDMS/ICP-MS. Lowest v alues. FeO (t).

81 . Penguin Island, XRF, IDMS, Fiv e bulk samples but only two for Keller et al. 1 992 highest ICP-MS IDMS/ICP-MS. Highest v alues. FeO (t).

82. South Sandwich Bulk samples, mean of two lav a samples, Fretzdorff and Smellie Islands FeO (t). 2002

83. Cape Purv is XRF, ICP-MS Lav a, bulk, Fe2O3 (t). Smellie et al. 2006. v olcano

84. Bridgeman ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Island, BI-01 , only a few were reported from 201 3 tephra EPMA/WDS. FeO (t).

85. Bridgeman ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Island, BI-02, only a few were reported from 201 3 tephra (welded) EPMA/WDS. FeO (t).

86. Bridgeman ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Island, BI-03, only a few were reported from 201 3 tephra (ash) EPMA/WDS. FeO (t).

87 . Bridgeman ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Island, BI-04, only a few were reported from 201 3 tephra (lapilli) EPMA/WDS. FeO (t).

88. Bridgeman ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Island, BI-05, only a few were reported from 201 3 pumice EPMA/WDS. FeO (t).

89. Bridgeman ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Island, BI-06, only a few were reported from 201 3 tephra EPMA/WDS. FeO (t).

102 90. Bridgeman ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Island, BI-07 , only a few were reported from 201 3 tephra EPMA/WDS. FeO (t).

91 . Bridgeman ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Island, BI-08, only a few were reported from 201 3 pumice & 1 bomb EPMA/WDS. FeO (t).

92. Cape Purv is, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press CP-01 , tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

93. Cape Purv is, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press CP-02, tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

94. Cape Purv is, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press CP-03, lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

95. Cape Purv is, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press CP-04, tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

96. Cape Purv is, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press CP-05, tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

97 . Cape Purv is, CP- ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press 06, bomb only a few were reported from 201 3 EPMA/WDS. FeO (t).

98. Cape Purv is, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press CP-07 , lav a w. CM only a few were reported from 201 3 & , tephra EPMA/WDS. FeO (t).

99. Cape Purv is, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press CP-08, tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 00. DI, DI-01 A, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 01 . DI, DI-01 B, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 02. DI, DI-02, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 03. DI, DI-04A, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 04. DI, DI-04B, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press bomb/clast only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 05. DI, DI-05A, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

103 1 06. DI, DI-05B, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 07 . DI, DI-06, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 08. DI, DI-07 , ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra & clasts only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 09. DI, DI-08A, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 1 0. DI, DI-08B, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press clasts only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 1 1 . DI, DI-09A, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 1 2. DI, DI-09B, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press clasts only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 1 3. DI, DI-1 0, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press bombs only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 1 4. DI, DI-1 1 , lav a ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 1 5. DI, DI-1 2B, fine ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press ash only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 1 6. DI, DI-1 3A, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press pumice/tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 1 7 . DI, DI-1 3B, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press obsidian only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 1 8. DI, DI-1 3C, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 1 9. DI, DI-1 4, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 20. DI, DI-1 5A, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 21 . DI, DI-1 5B, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra & clasts only a few were reported from 201 3 EPMA/WDS. FeO (t).

104 1 22. DI, DI-1 6A, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 23. DI, DI-1 6B, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press basalt clasts only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 24. DI, DI-1 7 , lav a ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 25. DI, DI-1 8, lav a ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 26. DI, DI-1 9, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 27 . DI, DI-20A, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 28. DI, DI-20B, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra & clasts only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 29. DI, DI-21 , lav a ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 30. DI, DI-22B, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press lapilli only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 31 . DI, DI-23, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 32. Inott Point, IP- ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press 01 , tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 33. Inott Point, IP- ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press 02A, tephra (lapilli) only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 34. Inott Point, IP- ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press 02B, pumice only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 35. Inott Point, IP- ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press 03A, lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 36. Inott Point, IP- ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press 03B, tephra (lapilli only a few were reported from 201 3 & pumice) EPMA/WDS. FeO (t).

1 37 . Melv ille Peak, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press MP-01 , tephra & only a few were reported from 201 3 clasts EPMA/WDS. FeO (t).

105 1 38. Melv ille Peak, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press MP-02, lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 39. Melv ille Peak, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press MP-03, tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 40. Melv ille Peak, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press MP-04, lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 41 . Melv ille Peak, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press MP-05A, tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 42. Melv ille Peak, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press MP-05B, tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 43. Melv ille Peak, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press MP-06A, tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 44. Melv ille Peak, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press MP-07 B, tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 45. Melv ille Peak, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press MP-1 0, tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 46. Melv ille Peak, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press MP-1 1 , tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 47 . Paulet Island, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press PAI-01 , lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 48. Paulet Island, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press PAI-02A, lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 49. Paulet Island, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press PAI-02B-1 , lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 50. Paulet Island, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press PAI-02B-2, lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 51 . Paulet Island, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press PAI-03, lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 52. Paulet Island, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press PAI-04A, red scoria only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 53. Paulet Island, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press PAI-04B, tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

106 1 54. Paulet Island, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press PAI-05A, tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 55. Paulet Island, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press PAI-05B, black only a few were reported from 201 3 scoria EPMA/WDS. FeO (t).

1 56. Penguin Island, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press PI-01 , lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 57 . Penguin Island, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press PI-02, tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 58. Penguin Island, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press PI-03, lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 59. Penguin Island, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press PI-04, tephra only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 60. Penguin ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Island, PI-05, only a few were reported from 201 3 tephra EPMA/WDS. FeO (t).

1 61 . Penguin Island, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press PI-06, lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 62. Rezen Peak, ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press RP-01 , lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 63. Seal Nunataks ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press (Larsen Nunatak), only a few were reported from 201 3 SN-01 , lav a EPMA/WDS. FeO (t).

1 64. Sail Rock, SR- ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press 01 , lav a only a few were reported from 201 3 EPMA/WDS. FeO (t).

1 65. Hurd P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press (Johnson's Dock), only a few were reported from 201 3 JD-01 , ice, tephra EPMA/WDS. FeO (t).

1 66. Hurd P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press (J´son's D.), JD-02, only a few were reported from 201 3 ice, tephra EPMA/WDS. FeO (t).

1 67 . Hurd P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press (Krumov K.), KK- only a few were reported from 201 3 01 , ice, tephra EPMA/WDS. FeO (t).

1 68. Hurd P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press (Perunika Glacier), only a few were reported from 201 3 LIT-01 , ice, tephra EPMA/WDS. FeO (t).

1 69. Hurd P. (P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Glacier), LIT-02, only a few were reported from 201 3 ice, tephra EPMA/WDS. FeO (t).

107 1 7 0. Hurd P. (P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Glacier), LIT-03, only a few were reported from 201 3 ice, tephra EPMA/WDS. FeO (t).

1 7 1 . Hurd P. (P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Glacier), LIT-04 (1 ), only a few were reported from 201 3 tephra EPMA/WDS. FeO (t).

1 7 2. Hurd P. (P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Glacier), LIT-04 only a few were reported from 201 3 (2), tephra EPMA/WDS. FeO (t).

1 7 3. Hurd P. (P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Glacier), LIT-05, only a few were reported from 201 3 tephra EPMA/WDS. FeO (t).

1 7 4. Hurd P. (P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Glacier), LIT-06, only a few were reported from 201 3 tephra EPMA/WDS. FeO (t).

1 7 5. Hurd P. (P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Glacier), LIT-07 , only a few were reported from 201 3 tephra EPMA/WDS. FeO (t).

1 7 6. Hurd P. (P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Glacier), LIT-08, only a few were reported from 201 3 tephra EPMA/WDS. FeO (t).

1 7 7 . Hurd P. (P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Glacier), PG-01 , only a few were reported from 201 3 tephra EPMA/WDS. FeO (t).

1 7 8. Hurd P. (P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Glacier), PG-02, only a few were reported from 201 3 tephra EPMA/WDS. FeO (t).

1 7 9. Hurd P. (P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Glacier), PG-03, only a few were reported from 201 3 tephra EPMA/WDS. FeO (t).

1 80. Hurd P. (P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Glacier), PG-04, only a few were reported from 201 3 tephra EPMA/WDS. FeO (t).

1 81 . Hurd P. (P. ICP-MS Bulk sample. All data is from ICP-MS, as Kraus et al. in press Glacier), PG-05, only a few were reported from 201 3 tephra EPMA/WDS. FeO (t).

1 82. Seal Nunataks, XRF, INAA Bulk sample. FeO (t). Hole 1 990, reported by R.37 1 3.4, basalt Kraus et al. in press 201 3

1 83. Seal Nunataks, XRF, INAA Bulk sample. FeO (t). Hole 1 990, reported by R.37 28.2, basalt Kraus et al. in press 201 3

1 84. Seal Nunataks, XRF, INAA Bulk sample. FeO (t). Hole 1 990, reported by R.37 29.1 , basalt Kraus et al. in press 201 3

1 85. Seal Nunataks, XRF, INAA Bulk sample.. FeO (t). Hole 1 990, reported by R.37 31 .3, basalt Kraus et al. in press 201 3

108 1 86. Seal Nunataks, XRF, INAA Bulk sample. FeO (t). Hole 1 990, reported by R.37 31 .4, basalt Kraus et al. in press 201 3

1 87 . Seal Nunataks, XRF, INAA Bulk sample. FeO (t). Hole 1 990, reported by R.37 35.1 , basalt Kraus et al. in press 201 3

1 88. Seal Nunatak, XRF, INAA Bulk sample. FeO (t). Hole 1 990, reported by R.37 39.2, basalt Kraus et al. in press 201 3

1 89. Seal Nunataks, XRF, INAA Bulk sample. FeO (t). Hole 1 990, reported by R.37 40.3, basalt Kraus et al. in press 201 3

1 90. Seal Nunataks, XRF, INAA Bulk sample. FeO (t). Hole 1 990, reported by R.37 42.3, basalt Kraus et al. in press 201 3

1 91 . Seal Nunataks, XRF, INAA Bulk sample. FeO (t). Hole 1 990, reported by R.37 46.1 , basalt Kraus et al. in press 201 3

1 92. Seal Nunataks, XRF, INAA Bulk sample. FeO (t). Hole et. 1 993, reported R.21 7 .4, basalt by Kraus et al. in press 201 3

1 93. Seal Nunataks, XRF, INAA Bulk sample. FeO (t). Hole et. 1 993, reported R.37 1 0.9, basalt by Kraus et al. in press 201 3

1 94. Seal Nunataks, XRF, INAA Bulk sample. FeO (t). Hole et. 1 993, reported R.37 28.1 , basalt by Kraus et al. in press 201 3

1 95. Seal Nunataks, XRF, INAA Bulk sample. FeO (t). Hole et. 1 993, reported R.37 34.1 , basalt by Kraus et al. in press 201 3

Table A5:3. Geochemistry data from areas other than the research area

A1 -2. New Zealand rhy olitic v olcanoes. Glass shards or crushed pumice analy sed. Method: Automated wav elength dispersiv e JEOL JXA-7 33 “superprobe” - probably WDS/WDXRA with EPMA (Stokes et al. 1 992).

A3-4. New Zealand, silicic rich mainly marine tephra. Glass shards. Method: EMP (electron microprobe) JEOL JXA-7 33 and more instruments - EPMA and others). The data is correlated with tephra from known v olcanoes which hav e been analy zed by other researchers - but the methods of analy sis are not reported in this paper (Pillans et al. 2005). The highest/lowest data tabulated are usually extremes v alues, and most v alues are in the middle of the range.

A5-8. Mount Moulton, Marie By rd Land, West Antarctica. Mount Berlin in this area is still thermally activ e. Consistent v ariation in chemical composition through time. Method: Electron microprobe with Back scattered- electron (BSE) imagery , on the glass phase of all sampled tephra lay ers. (Dunbar et al. 201 1 .)

A9-1 2. Marine sediments close to DI, with the same chemical composition as some eruptions from v olcanoes on Marie By rd Land, West Antarctica. The marine tephras were compared to tephras from different v olcanoes and ice cores, but these samples often had more extreme percentage v alues of all elements. It is astonishing how little v ariation there is in the abundance of the different elements in the marine sediments, ev en if the v ariation in nearby v olcanoes and ice core tephras v ary v ery much, and ev en if they are believ ed to hav e been deposited during c. 650 ka. Glass shards (from published SEM-photographs it is obv ious that not all of these are quartz grains). Methods: EPMA, IMA, EDAX (Hillenbrand et al. 2008. Rate data from table 4 in their supplementary data).

109 A1 3-1 7 . California, USA. 95-99% isotropic glass shards. Ta reacts with HF and v alues are therefore not trustable. (Knott et al. 2007 ) Methods: Major: EPMA Major in ppm (not tabulated) and minor/trace: S-ICP-MS

A1 8-20. Beringia. Old Crow tephra. Glass shards with a rhy olitic composition, sometimes probably with some minute amount of feldspar that was not possible to separate from the glass. Methods: EPMA, SN-ICP-MS, WDS, LA-ICP-MS. (Preece et al. 201 1 .) (Samples are v ery similar, so it is not necessary to use more than av erages.)

A21 -24. Siple Dome Ice Core, West Antarctica. Glass shards. Very large spread in v alues ev en within samples - one example tabulated - no. 657 c. This sample display a sy stematic coupled change for P, Si, Ti, Mg, Ca, and Fe. Method: EPMA. (Kurbatov et al. 2006.)

A25-26. Samples found at the Ty aty a v olcano, just north of Hokkaido, Japan. Samples hav e been identified as from Baltoushaun, China (c.1 500 km west of Ty aty a), and Komagatake, southern Hokkaido (c.500 km south of Ty aty a) (Nakagawa and Ohba 2002). Place/sample Methods Comments/discussion Reference

A1 . Okatina, New EPMA with WDS Mean from 1 0 places, only c. 1 0% of all Stokes et al. 1 992 Zealand, tephra v alues v aried more than c. 20%. FeO (t).

A2. Taupo, New EPMA with WDS Mean from 1 0 places, only c. 1 % (one Stokes et al. 1 992 Zealand, tephra percent) of all v alues v aried more than c. 20%. FeO (t).

A3. New Zealand EMP Lowest (often extreme) v alues from c. 1 50Pillans et al. 2005 tephras, lowest samples. FeO (t).

A4. New Zealand EMP Highest (often extreme) v alues from c. Pillans et al. 2005 tephras, highest 1 50 samples. FeO (t).

A5. Mount Berlin, EMP Lowest v alues from c. 50 samples. Mg- Dunbar et al. 201 1 West Antarctica, v alues between 0% and 0.82%. FeO (t). lowest, low-Mg- group

A6. Mount Berlin, EMP Highest v alues from c. 50 samples. Mg- Dunbar et al. 201 1 West Antarctica, v alues between 0% and 0.82%. FeO (t). highest, low-Mg- group

A7 . Mount Berlin, EMP Lowest v alues from sev en samples. Mg- Dunbar et al. 201 1 West Antarctica, samples between 3.89% and 6.93%. FeO lowest, high-Mg- (t). group

A8. Mount Berlin, EMP Highest v alues from sev en samples. Mg- Dunbar et al. 201 1 West Antarctica, samples between 3.89% and 693%. FeO highest, high-Mg- (t). group

A9. Lowest, marine, EPMA, IMA Lowest v alues of 1 5 samples, c. 801 -1 451 Hillenbrand et al. from Marie By rd, ka, FeO (t). 2008 close to DI

A1 0. Highest, EPMA, IMA Highest v alue of 1 5 samples, c. 801 -1 451 Hillenbrand et al. marine, from Marie ka, FeO (t). 2008 By rd, close to DI

A1 1 . Lowest, EPMA, IMA Lowest v alue of 1 7 samples, c. 801 -1 451 Hillenbrand et al. v olcanoes, ice cores ka, FeO (t). 2008

110 A1 2. Highest, EPMA, IMA Highest v alue of 1 7 samples, c. 801 -1 451 Hillenbrand et al. v olcanoes, ice cores ka, FeO (t). 2008

A1 3. Bishop EPMA, S-ICP-MS Lowest v alues, sev en samples, Fe2O3 (t) Knott et al. 2007 tuff/ash, USA, lowest

A1 4. Bishop EPMA, S-ICP-MS Highest v alues, sev en samples, Fe2O3 (t) Knott et al. 2007 tuff/ash, USA, highest

A1 5. Upper Glass M. EPMA, S-ICP-MS Mean of two samples, Fe2O3 (t) Knott et al. 2007 USA

A1 6. Lower Glass M. EPMA, S-ICP-MS One sample, Fe2O3 (t) Knott et al. 2007 USA

A1 7 . Mesquite EPMA, S-ICP-MS Mean of two samples, Fe2O3 (t) Knott et al. 2007 Spring, USA

A1 8. Beringia. Old EPMA, SN-ICP-MS, Lowest v alues from 27 sample sites. FeO Preece et al. 201 1 Crow tephra, lowest WDS, LA-ICP-MS (t). (After Rb not in table.)

A1 9. Beringia. Old EPMA, SN-ICP-MS, Highest v alue from 27 sample sites. FeO Preece et al. 201 1 Crow tephra, WDS, LA-ICP-MS (t). (After Rb not in table.) highest

A20. Beringia. Old EPMA, SN-ICP-MS, Av erage v alues from 27 sample sites. FeOPreece et al. 201 1 Crow tephra, WDS, LA-ICP-MS (t). av erage

A21 . Ice core, W. EPMA Circa 60 sample mesurements, lowest. Kurbatov et al. Antarctica, lowest 2006

A22. Ice core, W. EPMA Circa 60 sample measurements, highest. Kurbatov et al. Antarctica, highest 2006

A23. Ice core, W. EPMA Nine sample measurements from sample Kurbatov et al. Antarctica, 657 c, 657 c, lowest. 2006 lowest

A24. Ice core, W. EPMA Nine sample measurements from sample Kurbatov et al. Antarctica, 657 c, 657 c, highest. 2006 highest

A25. Japan, from EPMA One sample, as example. FeO (t). Nakagawa and China Ohba 2002

A26. Japan, from EPMA One sample, as example. FeO (t). Nakagawa and Hokkaido Ohba 2002

111 Appendix 6. Different statistical methods used in tephrochronology work

In tephrochronology work many different statistical methods have been used. In table A6:1 below is a short list, with some comments, to such statistical methods.

Table A6:1 . Statistical methods used for correlation of tephras.

1 . Biv ariate plots/Harker diagrams and other diagrams, with standard dev iation (Hunt and Hill 1 993, Pallàs et al. 2001 ).

2. CV = Coefficients of v ariation, and many more methods (e.g. ANOVA, MANOVA) are mentioned by (Lowe 201 1 ).

3. DFA = discriminant function analy sis, is a common method for statistically analy sing correlation of tephras (Stokes et al. 1 992, Hunt and Hill 1 993, Kuehn and Foit Jr. 2006). Both DFA and SC are described in Kuehn and Foit Jr. (2006), and Stokes et al. (1 992).

DFA is stated to more powerful than SC, but this may be because this is a more complicated method of analy sis and not that it will end up with a better result (Stokes et al. 1 992, showed a table comparing SC and DFA). For example, an analy sis has to be done of known units before unknowns can be identified. The nature of the reference data set control the outcome (Stokes et al. 1 992, Kuehn and Foit Jr. 2006). And, the data has to be pretreated to a logarithmic scale (Stokes et al. 1 992). The element with the most relativ e and abundant v ariability has greatest influence on the result of DFA, and therefore the data has to be transformed to a logarithmic scale (Shane and Froggatt 1 994). DFA only work well if it is known if the magmas are heterogenous or not (Lowe 201 1 ).

To use DFA usually a SAS-sy stem (and Mahalanobis), has to be used (e.g. Stokes et al. 1 992, p. 1 06, Shane and Froggatt 1 994).

Multinominal logistic regression is often preferred before DFA because it uses fewer assumptions; Jeromy Anglim´s blog: Psy chology and Statistics (July 201 2).

There are also many other problems with the method (e.g., see Shane and Froggatt 1 994, Lowe 201 1 ).

4. D = Distance function (Hillenbrand et al. 2008). (Euclidian) distance function D or D2, is a v ariant of SC (Lowe 2008). It is used by e.g. Preece et al. (201 1 ). It is a little more complicated than SC. It is not easy to use on single samples, because y ou need to know and compare the analy tical error of the samples. The statistical results sometimes do not show the correct answer (Dunbar and Kurbatov 201 1 ).

5. MSE = Mean standard error, used to identify tephra horizons (Ky lander et al. 201 1 ).

6. PCA = Principal component analy sis, and similar multiv ariate statistical methods. DCA= Detrended correspondence analy sis. RDA = Redundancy analy sis. CA/CCA= Canonical correspondence analy sis. All analy sed with the CANOCO programme. But, the methods smooth out extreme v alues. See Björck et al. (1 993), Björck and Zale (1 996a), Kuehn and Foit Jr. (2006).

There are some more problems with PCA and similar methods. (See Pearce et al. 2008.)

7 . Pearson correlation coefficient (Zale 1 994b).

8. SC = Similarity coefficient (Hunt and Hill 1 993, Narcisi et al. 2005, Kuehn and Foit Jr. 2006, Hillenbrand et al. 2008). This method is used with different equations, threshold v alue and elements in different papers, and correlations may still be inv alid (Hillenbrand et al. 2008, pp. 537 -538, Lowe 201 1 ). It is v ery simple and effectiv e but is not statistically rigorous (Kuehn and Foit Jr. 2006, but especially see: Knott et al. 2007 ). SC is difficult with major elements, better with minor elements (Knott et al. 2007 ). Lee et al. (2007 ) used this method, but ev en if the results were not positiv e (95%+) they correlated tephras with v olcanoes. The final decision if different tephras are correlated is still subjectiv e (Stokes et al. 1 992).

9. Student´s t-test is sometimes used (Denton and Pearce 2008, Lowe 2008, Lowe 201 1 ), albeit with strong disagreements from some (Lowe 2008).

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