A catalogue of major and trace element data for Icelandic Holocene silicic tephra layers

Tephra layers with Icelandic provenance have been identified across the North Atlantic region in terrestrial, lacustrine, marine and glacial environments. These tephra layers are used as marker horizons in tephrochronology including climate studies, archaeology and environmental change. The major element chemistries of 19 proximally deposited Holocene Icelandic silicic tephra layers confirm that individual volcanic systems have unique geochemical signatures and that eruptions from the same system can often be distinguished. In addition, glass trace element chemistry highlights subtle geochemical variations between tephra layers which appear to have identical major element chemistry and thus allows for the identification of some, if not all, tephra layers previously considered identical in composition. This paper catalogues the compositional variation between the widespread Holocene Icelandic silicic tephra deposits.     

Extending the limits of the Borrobol Tephra to Scandinavia and detection of new early Holocene tephras

Analyses of two infilled lakes in Blekinge, southeast Sweden, indicate the presence of at least three tephra horizons of Termination 1 and early Holocene age. Geochemical analyses confirm the presence of the Borrobol Tephra, the Askja Tephra (10,000 ¹⁴C yr B.P.), and one previously unreported tephra of Icelandic origin. Extending the limits of the Borrobol Tephra to Scandinavia illustrates that this ash is far more widespread than previously realized and is therefore, an important marker horizon for determining the rate and timing of the initial warming at the start of Greenland Interstade 1 (GI-1) within Europe. The relatively unknown Askja Tephra and the newly discovered Hässeldalen Tephra are stratigraphically placed at the Younger Dryas/Preboreal transition. This paper demonstrates the suitability and success associated with the extraction techniques for tracing microtephra horizons in areas distal to volcanic sources.     

Cryptotephrochronology of the Eemian and the last interglacial–glacial transition in the North East Atlantic

The Eemian interglacial and the onset of the subsequent glacial period serve as the most recent analogue for the natural operation of the climate system during the current interglacial. Pronounced climatic oscillations occurred during this period, but their nature and pattern are poorly understood due to dating limitations and unknown phase relationships between different regions and archives. Tephrochronology offers considerable potential for precise correlation of disparate palaeoclimatic archives preserving evidence of these rapid climatic transitions through the tracing of common isochronous tephra horizons. We outline the identification of three previously unknown cryptotephra horizons within a marine core from the Rockall Trough, North East Atlantic. This sequence preserves a high‐resolution record of this interval and shard size, geochemical heterogeneity and the co‐variance of shard concentrations with ice‐rafted debris data are utilized to demonstrate that primary airfall was the most likely transport and depositional pathway. The main geochemical populations of these horizons have similar transitional alkali major and trace element compositions, suggesting that they were derived from a common Icelandic source, potentially the Öræfajökull volcanic system. These tephra horizons represent additions to the North Atlantic event stratigraphy for this period and tentative correlations to Icelandic terrestrial deposits are proposed for two horizons.     

New major element analyses of proximal tephras from the Azores and suggested correlations with cryptotephras in North-West Europe

The Azores Archipelago is one of the most active volcanic areas in the North Atlantic region. Approximately 30 eruptions have been reported over the last 600 years with some major VEI 5 (Volcanic Explosivity Index) eruptions further back in time. The geochemical composition of associated tephra-derived glass, however, is not well characterized. An Azorean origin of cryptotephras found in distal areas such as North Africa, the British Isles and Greenland has been suggested, but proximal data from the Azores are scarce and the correlations have only been tentative. These tephras have a traychtic composition, which excludes an Icelandic origin. In a previous study, we presented major element analyses of proximal tephra-derived glass from five Holocene eruptions on the Azores Islands. There is a striking geochemical similarity between tephras from volcanoes on São Miguel and Irish cryptotephras, and especially with eruptives from the Furnas volcano. Here we present new analyses of proximal tephras that confirm and strengthen a link between Furnas and cryptotephras found in south-west Ireland. We also suggest a correlation between a previously unsourced tephra found in a Swedish bog with an eruption of the Sete Cidades volcano c. 3880 a cal BP.     

Three new distal tephras in sediments spanning the Last Glacial–Interglacial Transition in Scotland

Three new microtephras are reported from a number of lake sites from the Inner Hebrides and Scottish mainland. One occurs stratigrapically in the middle of Greenland Interstadial 1 (GI‐1) and has been named the Penifiler Tephra. It is rhyolitic and possesses a geochemical signature that is very similar to that of the Borrobol Tephra, which also occurs in three of the sequences reported here, but which lies close to the lower boundary of GI‐1. The second occurs stratigraphically in the early Holocene below the Saksunarvatn Ash and is named the Ashik Tephra. This tephra is geochemically bimodal, with a rhyolitic component comparable to the An Druim Tephra that occurs later in the Holocene, and a basaltic component which is similar to the Saksunarvatn Ash. A third tephra occurs stratigraphically above the Saksunarvatn Ash and is provisionally named the Breakish Tephra. The consistent inter‐site correlation demonstrated for these new tephras at several sites enhances the regional tephrostratigraphic framework, and increases the potential for correlating palaeoenvironmental events during GI‐1 and the early Holocene. However, the occurrence of multiple tephras with similar geochemistry in close stratigraphic and temporal proximity has implications for the rigour with which tephrostratigraphic investigations must be performed. Copyright © 2006 John Wiley & Sons, Ltd.     

Identification of Lower Pleistocene widespread tephras associated with large caldera-forming eruptions in the Tohoku area,north-east Japan

Tephra fingerprinting techniques contributing to volcanology and palaeoenvironmental studies have been developed using a combination of laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). In particular, femtosecond LA-ICP-MS can determine major- and trace element abundances in individual glass shards. On the basis of the major oxide and trace element composition of the glass shards, using those methods, we re-examined the identification of four lower Pleistocene tephras originating from north-east Japan. All trace element abundances exhibited the typical pattern of tephras from the Hokkaido–Tohoku area, and major element concentrations were distinct. As a result, we re-examined the correlation of the widespread Tmg-R4 tephra (2.0 Ma), and newly defined the widespread Kd44-Naka tephra (1.968–1.781 Ma), both originating from the Sengan geothermal region. Furthermore, we re-examined identifications of Sr-Asn-Kd8 (1.219 Ma) and Sr-Kc-U8 (0.922–0.910 Ma) in central Japan, both derived from the Aizu volcanic region. The extensive distributions of the former two tephras suggest the occurrence of two large caldera-forming eruptions (Volcanic Explosivity Index 7) during a short period. Also, the distributions and volumes of the latter two tephras are broader and larger than those previously assumed. The results provide insight into large volcanic eruption history and terrestrial and marine palaeoenvironmental history.     

Tephrochronology of the Toluca Basin,central Mexico

The major element glass geochemistry of 10 Late Pleistocene and Holocene tephras found in the Toluca Basin in the Trans-Mexican Volcanic Belt is reported for the first time, as a key step towards establishing a tephrochronology for the region. The context for this tephrochronology is provided by a review of Late Quaternary volcanism of the basin. New tephra samples were collected from reference profiles around the basin in order to establish major element glass geochemical data for tephras described in previous publications, but not previously analysed. In addition, cores were taken from the basin floor to extend the known spatial distribution of the tephra layers and establish correlations with the lacustrine record. Improved chronological control has been provided by seven new AMS and conventional radiocarbon dates on the major tephras. Geochemical data are presented for 10 tephras ranging in age from ca. 25,000 BP (Lower Toluca Pumice) to about 8500 BP (Tres Cruces Tephra). Based on geochemical data, it is possible to correlate between sites within the Toluca Basin and between the Toluca Basin and the Basin of Mexico. The basis for a tephrochronological framework has been established.     

Glacier Peak and mid-Lateglacial Katla cryptotephras in Scotland: potential new intercontinental and marine-terrestrial correlations

Using contiguous high resolution sampling methods, we report the detection of a Glacier Peak volcanic ash from North America in Lateglacial Interstadial lake sediments in western Scotland. It occurs in close proximity to the Icelandic Borrobol and Penifiler tephras, but is distinguishable by its rhyolitic major-element composition that is consistent with the earliest set G layer, one of a number of mid-Interstadial Glacier Peak eruptions dated between 13.71 and 13.41 cal ka bp. Another cryptotephra layer present in these same Interstadial sediments has a rhyolitic composition consistent with the Icelandic Katla source. However, it is in a stratigraphic position below the widespread mid-Lateglacial Stadial Vedde Ash from Katla, which is also present in these cores. The Katla layer is stratigraphically well defined, suggesting primary airfall, and is compositionally similar to a mid-Interstadial rhyolitic tephra reported from a North Atlantic marine sequence south of Iceland dated to ~13.6 ka. The detection of Glacier Peak G in the European tephrostratigraphy will permit direct high-precision correlation of mid-Interstadial palaeoenvironments between North American and European terrestrial sequences. Any correlation between the new Katla layer and similar marine layers remains provisional, though if verified would permit similar correlation between North Atlantic marine and European terrestrial records.     

Quaternary tephra marker beds and their potential for palaeoenvironmental reconstruction on Chatham Island,east of New Zealand,southwest Pacific Ocean

Tephras provide one of the most reliable methods of time control and synchronisation within Quaternary sequences. We report on the identification of two widespread rhyolitic tephras – the Kawakawa and Rangitawa tephras – preserved in extensive peat deposits on Chatham Island ～900 km east of New Zealand. The tephras, both products of supereruptions from the Taupo Volcanic Zone, occur as pale, fine‐ash dominated layers typically 10–150 mm thick. Mineralogically they are dominated by rhyolitic glass, together with subordinate amounts of quartz, feldspar, hypersthene, hornblende, Fe–Ti oxides and zircon. Phlogopite/biotite was identified additionally in Rangitawa Tephra. Ages for each tephra were obtained via mineralogical and major element glass composition‐based correlation with well‐dated equivalent deposits on mainland New Zealand, and we also obtained a new zircon fission‐track age for Rangitawa Tephra (350 ± 50 ka) on Chatham Island. Both tephras were erupted at critical times for palaeoenvironmental reconstructions in the New Zealand region: the Kawakawa at ca. 27 cal. ka, near the beginning of the ‘extended’ LGM early in marine isotope stage (MIS) 2; and the Rangitawa at ca. 350 ka near the end of MIS 10. The time constraints provided by the tephras demonstrate that Chatham Island peats contain long‐distance pollen derived from mainland New Zealand, which provides a reliable proxy for identifying glacial–interglacial climate conditions, in this case during the MIS 11–10 and MIS 2–1 cycles. The two tephras thus provide important chronostratigraphic tie‐points that facilitate correlation and synchronisation not only across the Quaternary deposits of the Chatham Islands group but also with climatically significant terrestrial and marine records in the wider New Zealand region. Copyright © 2010 John Wiley & Sons, Ltd.     

The use of microtephra horizons to correlate Late-glacial lake sediment successions in Scotland

Evidence is presented to show that two measurable concentrations of microtephra particles can be detected in deposits of Late Devensian Late-glacial age in three sites in Scotland. One layer is attributed to the Vedde Ash, a marker horizon within the Younger Dryas chronozone. The second is a new tephra reported for the first time, which we name the Borrobol Tephra. This occurs consistently near the base of the Late-glacial Interstadial organic sediments at each site, and is thought to date to around 12.5 ¹⁴C ka BP. Geochemical determinations using an electron microprobe confirm the identification of the Vedde Ash, suggest the Borrobol Tephra to have an Icelandic origin, and demonstrate the consistency of the geochemical signals at all three sites. © 1997 John Wiley & Sons, Ltd.     

Some numerical considerations in the geochemical analysis of distal microtephra

The use of Late Quaternary tephra horizons as isochronous markers for high resolution correlation between records is of growing importance in a number of scientific fields. Particular advancements have been made through the identification of microtephra deposits (very distal deposits of volcanic ash invisible to the naked eye). The successful correlation of ash layers and volcanic eruptions depends on the acquisition of the major element chemistries of a tephra layer, derived from microprobe analyses of individual glass shards. This is particularly important for microtephras where aeolian fractionation has removed much of the mineral phase of the ash deposit, which often aids tephra discrimination. There are, however, difficulties in distinguishing precisely between different eruptions of the same volcano using major element composition and this may not always be resolved by the use of trace elements. Given the potential of tephrochronology as a correlative tool in many disciplines it is important to resolve this difficulty. One way forward is to perform more robust statistical analyses on the geochemical data, as in general, analyses are confined to a series of bi-plots of major elements. Here the authors explore some of the problems associated with dealing with microprobe data generated for individual tephras and pay particular attention to the ‘unit sum problem’. Using a subset of data generated as part of a EURODELTA project on tephra distribution in the Adriatic, the authors demonstrate that this problem is detectable in major element data from tephras and have consequently applied the logratio method before further analyses of the data. It is demonstrated that the use of logratios combined with discriminant functions analysis provides a more robust assessment of likely chemical correlations between tephras, and are superior to the use of bi-plots alone; and obviate the need for any data normalization, a particular point of contention between tephrochronologists.     

Late‐glacial and Holocene palaeoceanography of the North Icelandic shelf

High‐resolution gravity cores and box cores from the North Icelandic shelf have been studied for palaeoceanographic history based on lithological and biostratigraphical foraminiferal data. Results from two outer shelf cores covering the last 13.6 k ¹⁴C yr BP are presented in this paper. The sediments accumulated in north–south trending basins on each side of the Kolbeinsey Ridge at water depths of ca. 400 m. Sedimentation rates up to 1.5 m kyr⁻¹ are observed during the Late‐glacial and Holocene. The Vedde and Saksunarvatn tephras are present in the cores as well as the Hekla 1104. A new tephra, KOL‐GS‐2, has been identified and dated to 13.4 k ¹⁴C yr BP, and another tephra, geochemically identical to the Borrobol Tephra, has been found at the same level. At present, the oceanographic Polar Front is located on the North Icelandic shelf, which experiences sharp oceanographic surface boundaries between the cold East Icelandic Current and the warmer Irminger Current. Past changes in sedimentological and biological processes in the study area are assumed to be related to fluctuations of the Polar Front. The area was deglaciated before ca. 14 kyr BP, but there is evidence of ice rafting up to the end of the GS‐1 (Greenland Stadial 1, Younger Dryas) period, increasing again towards the end of the Holocene. Foraminiferal studies show a relatively strong GS‐2 (pre‐13 kyr BP) palaeo‐Irminger Current, followed by severe cooling and then by unstable conditions during the remainder of the GI‐1 (Greenland Interstadial 1, Bølling–Allerød) and GS‐1 (Younger Dryas). Another cooling event occurred during the Preboreal before the Holocene current system was established at about 9 kyr BP. After a climatic optimum between 9 and 6 kyr BP the climate began to deteriorate and fluctuate. Copyright © 2000 John Wiley & Sons, Ltd.     

Fingerprinting the Late Pleistocene tephras of Ciomadul volcano,eastern–central Europe

Late Pleistocene tephras derived by large explosive volcanic eruptions are widespread in the Mediterranean and surrounding areas. They are important isochronous markers in stratigraphic sections and therefore it is important to constrain their sources. We report here tephrochronology results using multiple criteria to characterize the volcanic products of the Late Pleistocene Ciomadul volcano in eastern–central Europe. This dacitic volcano had an explosive eruption stage between 57 and 30 ka. The specific petrological character (ash texture, occurrence of plagioclase and amphibole phenocrysts and their compositions), the high-K calc-alkaline major element composition and particularly the distinct trace element characteristics provide a strong fingerprint of the Ciomadul volcano. This can be used for correlating tephra and cryptotephra occurrences within this timeframe. Remarkably, during this period several volcanic eruptions produced tephras with similar glass major element composition. However, they differ from Ciomadul tephras by glass trace element abundances, ratios of strongly incompatible trace elements and their mineral cargo that serve as discrimination tools. We used (U-Th)/He zircon dates combined with U-Th in situ rim dates along with luminescence and radiocarbon dating to constrain the age of the explosive eruptions of Ciomadul that yielded distal tephra layers but lack of identified proximal deposits.     

North European last glacial–interglacial transition (LGIT; 15–9 ka) tephrochronology: extended limits and new events

High‐precision correlation of palaeoclimatic and palaeoenvironmental records is crucial for testing hypotheses of synchronous change. Although radiocarbon is the traditional method for dating late Quaternary sedimentary sequences, particularly during the last glacial–interglacial transition (LGIT; 15–9 ka), there are inherent problems with the method, particularly during periods of climate change which are often accompanied by major perturbations in atmospheric radiocarbon content. An alternative method is the use of tephras that act as time‐parallel marker horizons. Within Europe, numerous volcanic centres are known to have erupted during the LGIT, providing considerable potential for high‐precision correlation independent of past radiocarbon fluctuations. Here we report the first identification of the Vedde Ash and Askja Tephra in Ireland, significantly extending the known provenance of these events. We have also identified two new horizons (the Roddans Port Tephras A and B) and tentatively recognise an additional horizon from Vallensgård Mose (Denmark) that provide crucial additional chronological control for the LGIT. Two phases of the Laacher See Tephra (LST) are reported, the lower Laacher See Tephra (LLST) and probably the C2 phase of the Middle Laacher See Tephra (MLST‐C2) indicating a more northeasterly distribution of this fan than reported previously. Copyright © 2006 John Wiley & Sons, Ltd.     

A Lateglacial–early Holocene tephrochronology for SW Sweden

Four cores from southwestern Sweden are presented together with their tephra geochemistry. Two cryptotephra horizons were confirmed geochemically in the cores, the Vedde Ash and the Hässeldalen Tephra. The Lateglacial Hässeldalen Tephra (11 360–11 300 cal. a BP) offers great potential as a regional isochrone to add a new degree of certainty to the deglaciation chronology of southern Sweden, including the extent of glacial Lake Bolmen. In addition, the geographical distribution of the Hässeldalen Tephra has recently been extended outside of Sweden, making it an important time‐marker horizon in northern Europe. There are potential difficulties, however. Proper identification of the actual isochrone is complicated by the vertical pattern of shard distribution, which could be the result of several eruptive events, as well as by the fact that shards from the 10‐ka Askja horizon (10 500–10 350 cal. a BP) were found in close stratigraphical proximity. The geochemical data presented are the result of improved EPMA methodology, which significantly reduces sodium mobilization. The results therefore have slightly altered values, which has consequences for classifying new finds when they are compared with previous data for geochemically similar tephras. Finally, potential indications of the Borrobol/Penifiler horizon are presented, although the existence of the horizon could not be confirmed geochemically. This highlights the need to retrieve cores from different locations within a basin based on an analysis of basin morphology if horizons are to be located.     

Correlation and characterisation of individual glass shards from tephra deposits using trace element laser ablation ICP‐MS analyses: current status and future potential

Laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) is a high spatial resolution analytical method which has been applied to the analysis of silicic tephras. With current instrumentation, around 30 trace elements can be determined from single glass shards as small as ～ 40 µm, separated from tephra deposits. As a result of element fractionation during the ablation process using a 266 nm laser, a relatively complex calibration strategy is required. Nonetheless, such a strategy gives analyses which are accurate (typically within ±5%) and have an analytical precision which varies from ～ ±2% at 100 ppm, to ～ ±15% at 1 ppm. Detection limits for elements used in correlation and discrimination studies are well below 1 ppm. Examples of the application of trace element analysis by LA‐ICP‐MS in tephra studies are presented from the USA, New Zealand and the Mediterranean. Improvements in instrumental sensitivity in recent years have the potential to lower detection limits and improve analytical precision, thus allowing the analysis of smaller glass shards from more distal tephras. Laser systems operating at shorter wavelengths (e.g. 193 nm) are now more widely available, and produce a much more controllable ablation in glasses than 266 nm lasers. Crater sizes of <10 µm are easily achieved, and at 193 nm many of the elemental fractionation issues which mar longer wavelengths are overcome. By coupling a short wavelength laser to a modern ICP‐MS it should be possible to determine the trace element composition of glass shards as small as 20 µm and, providing sample preparation issues can be overcome, the determination of the more abundant trace elements in glass shards as small as 10 µm is within instrumental capabilities. This will make it possible to chemically fingerprint tephra deposits which are far from their sources, and will greatly extend the range over which geochemical correlation of tephras can be undertaken. Copyright © 2007 John Wiley & Sons, Ltd.     

Tephra stratigraphy on the North Icelandic shelf: extending tephrochronology into marine sediments off North Iceland

Tephra stratigraphical and tephrochronological studies of marine core MD99‐2275 on the North Icelandic shelf have revealed 58 new tephra horizons within the last 7050 cal. a BP, bringing the total number of identified tephra layers to 76. So far, over 100 tephra layers have been identified in the entire core spanning the last 15 000 years. The majority of the newly identified tephra layers are basaltic in composition and originate from the most active volcanic systems in Iceland, namely Grímsvötn, Veidivötn‐Bárdarbunga and Katla. A total of 40 tephra layer land–sea correlations have been made within this time period, of which 16 represent absolutely dated tephra markers. In addition, two tephra marker series are revealed in the marine sediments and in the terrestrial tephra stratigraphy, located between c. 2300–2600 and between 5700–5900 years. For the last 15 000 years, 21 tephra markers have been recognized. The marine tephra layer frequency (TLF) reveals two peaks, within the last 2000 years, and between 5000 and 7000 years ago. It shows the same general characteristics as the terrestrial TLF curve in Iceland, which indicates that marine sediments can yield important information about volcanism in Iceland. This is useful in time segments in which terrestrial records are poor or non‐existent. The study contributes to a high‐resolution tephrochronological framework on the North Icelandic shelf, with core MD99‐2275 representing a potential stratotype section in the area, and for the northern North Atlantic–Nordic Seas region, as well as being an important contribution to the Lateglacial–early Holocene volcanic history of Iceland.     

Geochemistry,dispersal, volumes and chronology of Holocene silicic tephra layers from the Katla volcanic system,Iceland

At least 12 silicic tephra layers (SILK tephras) erupted between ca. 6600 and ca. 1675 yr BP from the Katla volcanic system, have been identified in southern Iceland. In addition to providing significant new knowledge on the Holocene volcanism of the Katla system which typically produces basaltic tephra, the SILK tephras form distinct and precise isochronous marker horizons in a climatically sensitive location close to both the atmospheric and marine polar fronts. With one exception the SILK tephras have a narrow compositional range, with SiO₂ between 63 and 67%. Geochemically they are indistinguishable from ocean transported pumice found on beaches in the North Atlantic region, although they differ significantly from the silicic component of the North Atlantic Ash Zone One (NAAZO). Volumes of airborne SILK tephra range from 0.05 to 0.3 km³. We present new isopach maps of the six largest layers and demonstrate that they originate within the Katla caldera. The apparently stable magma system conditions that produced the SILK tephras may have been established as a consequence of the eruption of the silicic component of NAAZO (ca. 10.3 ka) and disrupted by another large‐scale event, the tenth century ad Eldgjá eruption (ca. 1 ka). Despite the current long repose, silicic activity of this type may occur again in the future, presenting hitherto unknown hazards. Copyright © 2001 John Wiley & Sons, Ltd.     

New age estimates and climatostratigraphic correlations for the Borrobol and Penifiler Tephras: evidence from Abernethy Forest,Scotland

The emerging tephrostratigraphy of NW Europe spanning the last termination (ca. 15–9 ka) provides the potential for synchronizing marine, ice‐core and terrestrial records, but is currently compromised by stratigraphic complications, geochemical ambiguity and imprecise age estimates for some layers. Here we present new tephrostratigraphic, radiocarbon and chironomid‐based palaeotemperature data from Abernethy Forest, Scotland, that refine the ages and stratigraphic positions of the Borrobol and Penifiler tephras. The Borrobol Tephra (14.14–13.95 cal ka BP) was deposited in a relatively warm period equated with Greenland Interstadial sub‐stage GI‐1e. The younger Penifiler Tephra (14.09–13.65 cal ka BP) is closely associated with a cold oscillation equated with GI‐1d. We also present evidence for a previously undescribed tephra layer that has a major‐element chemical signature identical to the Vedde Ash. It is associated with the warming trend at the end of the Younger Dryas, and dates between 11.79 and 11.20 cal ka BP. Copyright © 2011 John Wiley & Sons, Ltd.     

Major and trace element abundances in volcanic glass shards in visible tephras in SG93 and SG06 drillcore samples from Lake Suigetsu,central Japan,obtained using femtosecond LA–ICP–MS

The major and trace element concentrations of volcanic glass shards from visible tephra layers in the SG93 and SG06 cores from Lake Suigetsu, central Japan, were determined by femtosecond laser ablation–inductively coupled plasma–mass spectrometry. The glass-shard analyses, together with the petrographic properties of the tephra samples, allow the Suigetsu tephra layers to be broadly classified into tephras derived from calderas on Kyushu Island, and from Daisen and Sambe volcanoes in the Chugoku district of southwest Japan. The layers correlated with tephras from Kuju caldera and Daisen volcano, and with the younger Sambe tephras, have adakitic elemental features. A Suigetsu tephra sample correlated with the Sambe−Kisuki tephra based on petrographic properties has an elemental pattern similar to that of the Toya tephra from Hokkaido Island, northeast Japan. This match implies that tephras from northeast Japan, as well as Kyushu–Chugoku tephras, are possible correlatives of the Suigetsu tephra layers. Both petrographic properties and major–trace element data of volcanic glass shards are essential for robust tephra correlations, and hierarchical cluster analysis proved additionally useful in statistically evaluating relationships among the tephras.