Visible Tephra Layers Research Articles

The Late Quaternary tephrostratigraphy of annually laminated sediments from Meerfelder Maar, Germany

The record of Late Quaternary environmental change within the sediments of Meerfelder Maar in the Eifel region of Germany is renowned for its high precision chronology, which is annually laminated throughout the Last Glacial to Interglacial transition (LGIT) and most of the Holocene. Two visible tephra layers are prominent within the floating varve chronology of Meerfelder Maar. An Early Holocene tephra layer, the Ulmener Maar Tephra (∼11,000 varve years BP), provides a tie-line of the Meerfelder Maar record to the varved Holocene record of nearby Lake Holzmaar. The Laacher See Tephra provides another prominent time marker for the late Allerød, ∼200 varve years before the transition into the Younger Dryas at 12,680 varve years BP. Further investigation has now shown that there are also 15 cryptotephra layers within the Meerfelder Maar LGIT-Holocene stratigraphy and these layers hold the potential to make direct comparisons between the Meerfelder Maar record and other palaeoenvironmental archives from across Europe and the North Atlantic. Most notable is the presence of the Vedde Ash, the most widespread Icelandic eruption known from the Late Quaternary, which occurred midway through the Younger Dryas. The Vedde Ash has also been found in the Greenland ice cores and can be used as an isochron around which the GICC05 and Meerfelder Maar annual chronologies can be compared. Near the base of the annual laminations in Meerfelder Maar a cryptotephra is found that correlates to the Neapolitan Yellow Tuff, erupted from Campi Flegrei in southern Italy, 1200 km away. This is the furthest north that the Neapolitan Yellow Tuff has been found, highlighting its importance in the construction of a European-wide tephrostratigraphic framework. The co-location of cryptotephra layers from Italian, Icelandic and Eifel volcanic sources, within such a precise chronological record, makes Meerfelder Maar one of the most important tephrostratotype records for continental Europe during the Last Glacial to Interglacial transition.

Millennial-scale reworking of tephra in alluvial to shallow marine settings: Distinguishing pseudo-isochrons from genuine ones

Primary tephra layers can provide isochrons in a stratigraphic sequence. Such isochrons are powerful tools in terms of correlation and chronology of strata, and they constrain a chronological framework for geology, geomorphology, archaeology and palaeo-environmental studies in the Neogene to Quaternary. However, reworking processes can re-distribute tephra materials in both time and space, so that a given tephra can form a new discrete layer later in the depositional sequence, or it can be distributed in low concentrations (no visible layers, i.e., crypto-tephras) over a range of different stratigraphic horizons. The present study, based on sedimentological, petrographical, and geochemical analyses of reworked tephras in Japan, evaluates the duration and persistence of reworking and the tephra mobilisation and delivery to watersheds. Furthermore, it discusses how a unique isochron can be constructed from tephra distribution in a sedimentary sequence. Examples presented here are from fluvial and deltaic sequences in the Japanese Quaternary, which contain several visible tephra layers and a certain amount of tephra materials from multiple sources at different stratigraphical horizons. In the Niigata Plain, 5.4ka Numazawako tephra material continued to be reworked for more than 4000 years after the eruption of Numazawa volcano, and was re-deposited as reworked pumice grains consisting of a “visible” tephra layer in delta front deposits. Mixed tephra materials originating from an earlier eruption of Numazawa volcano and eruptions from other calderas were also identified. In the Tsugaru Plain, post-2.5ka subsurface deposits have >10% glass shards content throughout the sequence. Glass shards were derived from several different tephra materials, such as those from the most recent eruption of Towada volcano (AD 915), and earlier caldera forming eruptions (30 ka, 15ka). Some of the glass shards probably originated from erosion of exposed Pliocene pyroclastic bedrock. Thus, tephra reworking processes in alluvial to shallow marine settings can continue long after an eruption has ended, and can persist even during inter-eruptive (i.e., background sedimentation) periods. As tephra reworking involves complicated processes, careful observation and interpretations are necessary to evaluate whether tephra materials can truly provide an isochron for the strata in which they are found to exist.

The cultural nature of tephra: ‘Problematic’ ecofacts and artifacts and the Barú volcano, Panamá

This paper presents data from archaeological stratigraphy and lacustrine core samples containing tephra from the Barú volcano in western Panama. The discussion seeks to refine the understanding of medial tephra deposits near Barú in relation to the eruption history indicated by geological, palaeoecological, and archaeological data. A primary goal of this fieldwork is the identification and correlation of tephra from major Barú eruptions encountered in archaeological contexts by their lithology, stratigraphic position, and mineralogy without resorting to geochemical fingerprinting. The intention is to develop a cost efficient and reproducible means of utilizing tephra as a chronostratigraphic marker in archaeological contexts and examine the intersection of human life with volcanic events and dynamic environments. Tephra in archaeological contexts can have ambiguous placement between ecofact and artifact, as is the case with a small number of crude tephra sculptures in my excavated material and that of a seminal prior study. While the research project utilizes visible tephra layers, not cryptotephra, by all means the tephra data prove to be cryptic. Engagement with the imperfection entailed in meshing multidisciplinary data sets and different scientific communities with interests in tephra, particularly in lesser studied regions, is posited as a ‘total’ view of tephra.

Geochemical multielement signatures of glacial and interglacial facies of the Okhotsk Sea deepwater sediments during the past 350 kyr: A response to global climate changes at the orbital and millennial scales

AbstractThe previously dated deepwater sediment core MR06‐04 PC‐7R (length 1723 cm; 350 kyr) recovered from the central Okhotsk Sea (OS) was analyzed for biogenic compounds and for 63 chemical elements (using the inductively coupled plasma–mass spectrometry method) with a high resolution (1 cm; ~200 years). A one box model with two main members” and mathematical methods (based on multielemental composition of sediments) for the calculation of weight fractions (at each time slice) of two main types of geochemical facies that dominate during considerably diverse climatic periods (glacial maxima and interglacial optima) were proposed and tested. This model can be applied to other analogous natural systems whose sedimentation is driven by two main types of geochemical facies. The application of the developed model to the studied core revealed that variations of weight fractions of the typical interglacial and glacial geochemical facies in the sediments along the core depth (named as warm and cold “covariators,” respectively) change synchronously with global and regional climate variability. Profiles of warm and inversed cold covariators coincide tightly, and their values increase during warm marine isotope stages and substages and decrease during cold ones over the last 350 kyr. Millennial scale changes in covariators had occurred simultaneously with abrupt variability in the OS productivity and sediment lithology and with millennial global climate variability. Some discrepancies in the warm and inversed cold covariators calculated using specific mathematical treatments revealed the episodic influence of volcanogenic matter presented in the core by visible tephra layers and cryptotephras.

A multidisciplinary approach for reconstructing the stratigraphic framework of the last 40 ka in a bathyal area of the eastern Tyrrhenian Sea

A detailed integrated stratigraphic framework for the last 40ka in the eastern Tyrrhenian Sea (central Mediterranean) was obtained through quantitative analyses of planktonic foraminifera assemblages, tephrostratigraphical studies and δ18O measurements on the basinal CET1 cored succession.Relative abundance fluctuations in the planktonic foraminifera assemblages allowed the identification of nine known eco-biozones and several bioevents recognized in the Tyrrhenian area and that are useful for correlations between Mediterranean marine records. Compositional changes in the planktonic foraminifera assemblages together with variations in the oxygen isotope record allowed us to detect the major climatic global fluctuations and some of the minor events that occurred during the investigated time interval.A total of 12 visible tephra layers and cryptotephras have been recognized and correlated with their volcanic sources and/or with known explosive events of Campanian and Sicilian–Aeolian volcanoes.A stratigraphic relationship between foraminiferal and climatic events and tephra layers has been highlighted. For the first time ecostratigraphic and tephrostratigraphic methods were combined to obtain a detailed integrated stratigraphy for the last 40ka in the Tyrrhenian area. The achieved stratigraphic framework provides a useful stratigraphic reference record for the investigated area.

The detailed tephrostratigraphy of a core from the south‐east Black Sea spanning the last ∼60 ka

ABSTRACTOne visible volcanic ash layer and 21 non‐visible, cryptotephra horizons have been identified in the M72/5‐25‐GC1 core from the south‐east Black Sea that spans the last ∼60 ka. Glass chemistry suggests that the tephras derive from Italian, Hellenic and Turkish sources. The visible tephra layer is trachytic in composition and has been correlated to the ∼39 ka Campanian Ignimbrite super‐eruption from Campi Flegrei caldera, Italy. Two cryptotephra layers are associated with eruptions from Acigöl volcano (Turkey) around the Last Glacial Maximum, another is linked to activity at Erciyes Dagi in the Early Holocene (Perikartini or Karagüllü), and a cryptotephra layer near the top of the core correlates to the ∼3.6k cal a BP Minoan (marine Z2) tephra from Santorini (Thera), Greece. This extends the known dispersal area for all these volcanic ash units. Many other calc‐alkaline rhyolite layers preserved in the core are likely to be from central Anatolian sources but the lack of detailed proximal data for many of the volcanoes in the region prohibits further correlations. The tephrostratigraphy and glass compositional data presented here allow the tephra layers to be used to correlate sedimentary archives across the region, and help to extend the Mediterranean tephrochronology framework towards the east.

Volcanic ash layers in Lake El'gygytgyn: eight new regionally significant chronostratigraphic markers for western Beringia

Abstract. Ash layers from explosive volcanic eruptions (i.e., tephra) represent isochronous surfaces independent from the environment in which they are deposited and the distance from their source. In comparison to eastern Beringia (non-glaciated Yukon and Alaska), few Plio-Pleistocene distal tephra are known from western Beringia (non-glaciated arctic and subarctic eastern Russia), hindering the dating and correlation of sediments beyond the limit of radiocarbon and luminescence methods. The identification of eight visible tephra layers (T0–T7) in sediment cores extracted from Lake El'gygytgyn, in the Far East Russian Arctic, indicates the feasibility of developing a tephrostratigraphic framework for this region. These tephra range in age from ca 45 ky to 2.2 My old, and each is described and characterized by its major-, minor-, trace-element and Pb isotope composition. These data show that subduction-zone-related volcanism from the Kurile–Kamchatka–Aleutian Arc and Alaska Peninsula is the most likely source, with Pb isotope data indicating a Kamchatkan volcanic source for tephra layers T0–T5 and T7, while a source in the Aleutian Arc is possible for tephra T6. The location of Lake El'gygytgyn relative to potential source volcanoes (> 1000 km) suggests these tephra are regionally distributed over a large area. These deposits provide a unique opportunity to correlate the high-resolution paleoenvironmental records of Lake El'gygytgyn to other terrestrial paleoenvironmental archives from western Beringia and marine records from the western North Pacific and Bering Sea, and to move towards the development of a robust integrated framework between the continuous paleoclimatic records of Lake El'gygytgyn and other terrestrial and marine records in NE Eurasia.

Chronicle of regional volcanic eruptions recorded in Okhotsk Sea sediments over the last 350 ka

Recovered from the central Okhotsk Sea, the dated marine sediment core MR PC-7R was used to reconstruct the history of volcanic eruptions taking place over the last 350 ka in the Kuril–Kamchatka area, one of the most active volcanic regions in the world. Three visible tephra layers previously identified in Okhotsk Sea sediments were identified in this core. A novel approach was applied to detect traces of tephra fallout from ancient eruptions, namely cryptotephras, based on the elemental content of bulk sediment and a new lithological index. The concentrations of 63 elements in 1723 samples of bulk sediment sampled every 1 cm throughout core length were measured via ICP-MS analysis, with an average resolution time of 200 years. Factor analyses of these 63 elements plus 2 further variables enabled the identification of Factor 1 elements, which had lowered content in tephra, and those in the Factor 2 group, with elevated content in tephra. A Volc/Ter ratio determined under a binocular microscope by means of visual assessment of volcanic and terrigenous grains in the >63 μm sediment fraction was used as an independently measured index of cryptotephra occurrence. The factor analysis and Volc/Ter ratio were then employed to facilitate the detection of cryptotephras in the sediments, with 31 detected in addition to the three visible tephra for the last 350 ka. The previously constructed age model for the core, based on marine isotope stages/sub-stages and millennial-scale cold events, allowed us to determine the age and stratigraphy of the newly-identified cryptotephras and therefore also of ancient regional eruptions.

Distal occurrence of mid-Holocene Whakatane Tephra on the Chatham Islands, New Zealand, and potential for cryptotephra studies

The Whakatane Tephra, a rhyolitic tephra erupted ca. 5500 cal. BP from Okataina Volcanic Centre, central North Island, has been identified on the Chatham Islands which lie ∼900 km east of Christchurch, New Zealand. The visible tephra layer, ∼5 mm in thickness and preserved within peat on Pitt Island, was identified using both radiocarbon dating and analysis of glass shards by electron microprobe. Whakatane Tephra is the first Holocene tephra to be identified on the Chatham Islands, and it is the most-distal Holocene tephra yet recorded in the New Zealand region, being ∼850 km from source. The Pitt Island occurrence extends the tephra’s dispersal area markedly, by an order of magnitude, possibly to ∼300,000 km 2. An estimated dispersal index ( D) of approximately 10 5 km 2 indicates that the eruption generated a very high plinian column, possibly exceeding ∼30 km in height, with strong winds blowing the ash plume southeastwards. This new discovery of distal Whakatane Tephra as a thin but visible layer strongly implies that cryptotephras are likely to be preserved on the Chatham Islands and within adjacent ocean floor sediments. Therefore the potential exists to develop enhanced cryptotephrostratigraphic records from these distal areas, which in turn would help facilitate precise correlation via tephrochronology of palaeoenvironmental records (such as NZ-INTIMATE) from mainland New Zealand, the southwest Pacific Ocean, and the Chatham Islands.

Characterization and correlation of cryptotephras using major-element analyses of melt inclusions preserved in quartz in last interglacial marine sediments, southeastern Shikoku, Japan

Although sediments underlying marine terraces in SE Shikoku, southwest Japan, contain no visible tephra layers, late Pleistocene cryptotephras were detected in a paleosol within the sediments. The cryptotephras contained little or no glass, but they were characterized through major-element analyses of glass preserved as melt inclusions in quartz grains extracted from the paleosol. The analyses enabled correlation of the cryptotephras with known eruptives from volcanoes on Kyushu, namely the Kikai-Tozurahara tephra (MIS 5.2–5.3), the Aira-Tn tephra (28.6 cal ka), and the Kikai-Akahoya tephra (7.5 cal ka). These correlations enabled dating of the marine terrace surface known as the Murotomisaki 1 surface in SE Shikoku as being older than MIS 5.2–5.3, probably MIS 5.5 in age. In the absence of glass or mafic minerals because of weathering, the analysis of melt inclusions in resistant quartz grains demonstrably provides a powerful method for characterizing cryptotephras to facilitate their correlation and thus their application as a linking and dating tool.

Geochemistry of Holocene cryptotephras from the North Iceland Shelf (MD99-2269): intercalibration with radiocarbon and palaeomagnetic chronostratigraphies

Tephra-grain counting, morphology and geochemistry in the 150–1000 μm size fraction were used to identify 22 individual tephra horizons and one visible tephra layer (Saksunarvatn) from postglacial sediment of the north Iceland shelf. Core MD99-2269 (66°37.53‘N, 20°51.16‘W, water depth 365 m, length 2533 cm) from the Reykjafjardaráll basin is constrained at the base by the Vedde tephra (c. 12 000 cal. yr BP). Geochemical analyses and stratigraphical position of the 22 tephra horizons were used to identify the following cryptotephras: KOL-1372 (AD 1372), Hekla 1104 (AD 1104), Snæfellsnes 1 (c. 1790 cal. yr BP), Hekla 3 (c. 2970 cal. yr BP), Hekla 4 (c. 4230 cal. yr BP), TV 5 (c. 6860 cal. yr BP) and Suduroy (c. 8070 cal. yr BP). A tephra of the same geochemistry as KOL-1372 was found near the base of the core and is here named KOL3-2269 (>11 000 cal. yr BP). Eleven additional cryptotephras were geochemically typed to their respective Icelandic volcanic centres of origin and their ages constrained. Four tephra horizons had a very heterogeneous geochemical signal and may reflect secondary rather than primary deposition although we speculate whether the heterogeneity may be due to mixing of distinct cryptotephras within our sample. The cryptotephras and one visible tephra layer (Saksunarvatn) were intercalibrated with the combined MD99-2269 and MD99-2322 (67°08.18‘N, 30°49.67‘W, 714 m water depth, length 2617 cm) palaeomagnetic secular variation record, in depth and on a calibrated radiocarbon chronology, providing a fundamental chronological and stratigraphic template for future studies of environmental and volcanic variability for the Icelandic region, eastern North Atlantic and NW Europe.

極域アイスコアに記録された地球環境変動

This paper describes past climate and environmental changes during the past 101 to 105 year time scale obtained by recent studies on ice cores from Arctic and Antarctica. Shallow ice cores from Greenland and Svalbard show clear North Atlantic Oscillation (NAO) signals and explosive volcanic activities in the Northern Hemisphere and the equatorial regions. A deep ice core drilled to 2503 m at Dome Fuji, Antarctica covers the past 320 ka, which includes 3 glacial-interglacial cycles with Milankovitch cycles of about 20, 40, and 100 ka. Major chemical compositions and microparticle flux show high concentrations in glacials and low concentrations in interglain high-middle latitudes during glacial-interglacial cycles. The Dome Fuji deep ice core contains 25 visible tephra layers. An analysis of the chemical compositions shows the possible source volcanoes in and around the Antarctica.

Chemical composition of volcanic glasses in visible tephra layers found in a 2503 m deep ice core from Dome Fuji, Antarctica

AbstractTwenty-six ash layers were found in a 2503 m deep ice core from Dome Fuji station, East Antarctica. In order to gain information about the sources of ash particles found in the layers, major and trace element abundances have been measured. The particles found in 21 of the 26 layers were commonly a few tens of μm in size, suggesting that they originated from volcanoes located in and around the Antarctic. On the basis of comparison of the major-element compositions of these tephras with reference to volcanic rocks and ash, the tephras were divided into three types: (1) tholeiitic basalt to dacite, (2) calc-alkaline andesite, and (3) trachyandesite to trachyte. The source regions appear to be (1) South Sandwich Islands, Southern Ocean, (2) South Shetland Islands, Antarctica, and/or a southern part of the volcanic zone of the Andes, and (3) Marie Byrd Land and/or Victoria Land, Antarctica, respectively. The tephras found in the other five ash layers were significantly smaller (< 5 μm), suggesting that they traveled over longer distances. Abundances of trace elements for the alkaline tephra collected from one layer revealed a possible genetic link to volcanic rocks from Marie Byrd Land. In order to correlate between ice cores from Dome Fuji and Vostok, Antarctica, which are widely separated, we found coeval ash layers serving as stratigraphic markers of Antarctic ice cores. A comparison of profiles of 18O/16O (δ18O) and 2H/1H (δD) for the Dome Fuji and Vostok cores indicates that eight ash layers are equivalent in the two cores. A clear correlation was found for the chemical compositions of six of these ash layers, indicating a high potential for key correlation beds between the deep ice cores from Dome Fuji and Vostok.

Volcanic layers in Antarctic (Vostok) ice cores: Source identification and atmospheric implications

Fifteen visible volcanic ash layers (tephra) from Vostok ice cores have been analyzed for major elements, trace elements, and Sr and Nd isotope composition. Comparison of their geochemical signatures to lava composition from the inventory of Antarctic and subantarctic volcanoes, which have been active over the last 0.5 million years, indicates that nine layers originate from activity of the South Sandwich volcanic arc, three from southern South America, one from the Antarctic Peninsula (Bransfield Strait), and one from West Antarctica (Marie Byrd Land province). The large size of the tephra (up to 50 μm) requires rapid atmospheric transfer from the volcanic centers to East Antarctica. Rapid tropospheric transport from the southwestern Atlantic, penetrating East Antarctica, therefore predominates during the period studied, whether in glacial or interglacial climatic mode. In spite of the low frequency of occurrence of visible tephra layers in Vostok core (one event every 20 kyr), the overall atmospheric pathway of these ash events appears consistent with the almost continuous advection of continental dust from South America.

Tephra layers in the Dome Fuji (Antarctica) deep ice core

AbstractA deep ice core drilled to 2503 m depth at Dome Fuji, Antarctica, contains 25 visible tephra layers during the past 340 ka. The thickness of tephra layers is in the range 1-24 mm. The thickness and duration at deposition, determined by a simple ice-flow model, suggests that a violent volcanic eruption caused ash to fall onto the Antarctic ice sheet for ~5 years and to form a ~100 mm thick tephra layer at 117 ka BE Two tephra layers at depths of 573 and 2202 m probably originated from volcanoes in the South Sandwich Islands, Southern Ocean, given the size of tephra shards, >20μm in diameter, and their major chemical composition. Only eight of the 25 tephra layers can also be recognized in the Vostok (Antarctica) ice core, but all correspond to the Vostok tephras if we consider cloudy bands to be volcanic.

Deep ice-core drilling at Dome Fuji and glaciological studies in east Dronning Maud Land, Antarctica

The Dome Fuji Project is a comprehensive study of present and past glaeiological/climatological features of the Antarctic ice sheet in east Dronning Maud Land. Field observations on a 100U km traverse route from the coast to Dome Fuji slum changes in various glaciological parameters with surface elevation and distance from the coast. Deep ice-core drilling at Dome Fuji was started in August 1995 and reached a depth of 2503.52 m in December 1996. in situ core analyses revealed 25 visible tephra layers and a number of distinct cloudy bands in the ice.