Toba Ash Research Articles

Sea surface acidification events in the Andaman Sea associated with the last Toba volcanic activity

To date, little is known about the impact of super-eruptions on ocean biogeochemistry. Using boron isotopes ratios measured on planktonic foraminifera in the marine sediment core BAR94–25, we provide a high-resolution pH record in the Andaman Sea (North of Sumatra), spanning Marine Isotopic Stage 5 to 3. This transition encompasses the super-eruption of the Toba volcano, 74,000 years ago, making it possible to decipher the potential impact of the super-eruption emissions on the ocean pH for the first time. Our results show that inferred foraminiferal pH values generally follow those predicted by glacial-interglacial CO2 variations. However, several abrupt pH drops coincide with Toba ash deposition. This suggests the occurrence of acidification events possibly related to Toba volcanic sulphur emission episodes. These pH drops are followed by anomalous pH increases, possibly relating to localised increases in seawater alkalinity following the alteration of large ash deposits on land.

Revisiting the occurrence and distribution of Indian Ocean Tephra: Quaternary marine Toba ash inventory

The Toba Caldera on Sumatra, Indonesia is the host of the Young Toba eruption (∼74 ka), globally one of the largest and most recognized eruptions during the Quaternary and regionally concentrated in the eastern Indian Ocean. Three older deposits (Middle, and Old Toba Tuff as well as Haranggaol Dacite Tuff) are also attributed to Toba caldera, with their eruption products distributed over the Indian Ocean.We present the Quaternary marine tephra record from an array of 14 sites and 28 holes from deep ocean drilling programs, complementing earlier work on distal to ultra-distal Indian Ocean sediment cores and terrestrial distribution data of Toba deposits. A unique set of major and trace element glass-shard compositions on 115 primary ash layers together with glass shard morphologies, core pictures and statistical analysis support geochemical fingerprinting between marine tephra layers and known deposits from Toba and five so far unidentified medium to large eruptions assigned to northern Sumatra. Additionally, zircon crystallization ages have been determined for the Haranggaol Dacite Tuff resulting in a new maximum eruption age of 1.42 ± 0.034 Ma.Tephra volumes and magma masses for the (co-ignimbrite) fallout are estimated based on the compiled marine tephra distribution that are complemented by published proximal ignimbrite volumes. For YTT the resulting tephra and DRE volumes of 5600 km3 and 3600 km3, respectively, are in between the previous estimates. For MTT (253 km3 DRE), ODT (1550 km3 DRE), HDT (129 km3 DRE), and the five additionally identified eruptions from Northern-Sumatran volcanoes, new magma volumes have been determined. Overall, the Indian Ocean tephra record reveals in one large eruption every 200 kyr in the Quaternary that is derived from northern Sumatra. Plain language summaryThe Toba Caldera on Sumatra, Indonesia, is a famous spot for volcanism since it is the host of one of the largest and most recognized eruptions on the world, the ∼74 ka Young Toba supereruption. It produced widespread volcanic particles (volcanic ash) that were distributed around the globe by winds, but most deposits are concentrated in the eastern Indian Ocean. Next to the Young Toba Tuff (YTT), three older deposits from probably similar large eruptions are known from this caldera that are also found as ash layers in the Indian Ocean.We investigated this marine tephra record, including 28 locations from the three phases of the deep ocean drilling program (DSDP, ODP, IODP), and created a unique set of glass-shard trace element (LA-ICP-MS) compositions that complements our major element (EMP) data on 115 primary ash layers. Comparing these compositions between the different marine locations and to known terrestrial deposits of the Toba eruptions is done by geochemical fingerprinting where the characteristic chemical “fingerprint” of marine ash layers is correlated between oceanic and to on-land deposits to find out from which eruption it originated. Glass shard morphologies, core pictures and statistical analysis complement this approach to support the correlations to four known tephras from Toba (Young, Middle, and Old Toba Tuff, as well as Haranggaol Dacite Tuff) and five so far unidentified eruptions from Northern Sumatra.The distribution of all tephras in the Indian Ocean allows to estimate erupted volumes by mapping out the occurrence and thicknesses of the tephras on the seafloor using drill cores. The resulting magma volumes amount to, for example, between 3600 km3 and 129 km3 magma for Young, Middle, and Old Toba Tuff as well as the Haranggaol Dacitic Tuff. Together with the five additionally identified (northern)Sumatra eruptions, these results indicate that one large eruption has happened every 200 kyr in northern Sumatra over the last 2.4 Ma.

First Report of Toba Ash Bed from the Himalayan Foot-Hill Alluvial Fan Deposit, Neora River Section, Jalpaiguri District, West Bengal and its Implication

First Report of Toba Ash Bed from the Himalayan Foot-Hill Alluvial Fan Deposit, Neora River Section, Jalpaiguri District, West Bengal and its Implication

Late Quaternary sediments from Barakar-Damodar Basin, Eastern India include the 74 ka Toba ash and a 17 ka microlith toolkit

The Youngest Toba Tuff (YTT, 74 ka ago) is considered as the product of one of the largest super-volcanic events in the Quaternary period, which possibly caused a disastrous effect on the climate and hominid habitation. Here, we report a rare occurrence of an ∼ 2 cm YTT ash bed in the Barakar-Damodar Late Quaternary sediments, Eastern India, and the Microlith toolkits that were found in the sedimentary deposits above the ash layer. The high silica content of the glass shards with bubble walls, blocky, rod-shaped structures, and pumice morphology, are similar to other YTT ash deposits. The sedimentary facies associated with the ash layer show a transition from lacustrine to fluvial depositional environments. Sedimentological, petrographical, mineralogical, geochemical, and magnetic properties suggest the ash was deposited in a lacustrine environment. Moreover, the discovery of the ash bed, the occurrence of in-situ Bovid species, and microlith assemblages in the Barakar-Damodar Valley add to our understanding of late Pleistocene depositional environments, hominin occupations, and possible local migration across eastern India during the Last Glacial Maximum (LGM) period.

Palaeolithic assemblages associated with Youngest Toba Tuff deposits from the upper Gundlakamma River basin, Andhra Pradesh, India

Abstract Archaeological and geological remains associated with the Youngest Toba Tuff (YTT) deposits in India are seen as significant proxies for reconstructing (1) initial modern human colonization of India and (2) possible climatic impacts of the Toba super-eruption of 74 ka on the Indian climate and hominin behaviour. In order to gain further insights into the environmental impacts and behavioural adaptations of human populations in India before and after the Toba eruption, we investigated archaeological horizons associated with the Toba ash beds along the Gundlakamma basin in Prakasam District, Andhra Pradesh, India. Here, lithic artefacts were identified below and above the YTT deposits. The YTT deposits in the Gundlakamma River basin have a maximum thickness of 50 cm, comparatively thinner than those at the better investigated valleys of the adjacent Jurreru and Sagileru in Andhra Pradesh and the Son, Madhya Pradesh, India. Our surveys indicate that the Palaeolithic assemblages associated with YTT deposits from the Gundlakamma River basin can provide significant insights into the issues and debates surrounding the Toba archaeology.

Lenggong Valley – Revisit Our National Treasure

Lenggong Valley was incepted as UNESCO World Heritage Site in 2012 for its marvellous cultural value. However, the status will be in peril if the valley is left neglected and nothing is done. The area is renowned for the discovery of prehistoric human settlement. Numerous studies and researches have been conducted at Lenggong Valley to increase the scientific knowledge of the surrounding areas for further conservation and development. Toba ash deposit from volcanic eruption in Sumatra, Indonesia and possible meteorite impact were also discovered within the valley. Geoelectrical resistivity survey have been conducted to determine the thickness of Toba ash. The results were correlated with borehole log from the Department of Mineral and Geoscience Malaysia (JMG), that shows the Toba ash layer is around 10 m in depth and presents low resistivity range of values (<100 Ωm). Water geochemical analysis at one of the known water spring shows the surface temperature is 27.6 °C, with a pH value of 7.47. Truth be told, Lenggong Valley has a diversity of archaeological sites and geosites that can be established as a geopark and a group of committee will be materializing it in year 2021 or 2022.

Correlation Problem in Quaternary Stratigraphy, Prehistrory and Archaeostratigraphy in India: Role of 75 Ka Toba Ash Bed Markers

Archaeology & Anthropology: Open Access Correlation Problem in Quaternary Stratigraphy, Prehistrory and Archaeostratigraphy in India: Role of 75 Ka Toba Ash Bed Markers Acharyya SK* Department of Geological Sciences, Jadavpur University, India *Corresponding author: Acharyya SK, Emeritus Scientist, Department of Geological Sciences, Jadavpur University, Kolkata-32, India Submission: September 11, 2017; Published: November 29, 2017 DOI: 10.31031/AAOA.2017.01.000512 ISSN: 2577-1949Volume1 Issue3

Comment on “The Latest on Volcanic Eruptions and Climate”

Alan Robock (Eos, 94(35), 305–306, doi:10.1002/2013EO350001) nicely summarizes past volcanic eruptions and climate, but we wish to correct his assessment of our recent discovery of the Youngest Toba ash in the sediments of Lake Malawi in East Africa [Lane et al., 2013].

Clay Mineralogy of the Pleistocene Soil Horizon in Barind Tract, Bangladesh

Abstract Pleistocene red soil horizons were exposed in different areas of the Barind Tract in north-west Bangladesh. X-ray diffractions of twenty seven samples from different depths of these soil horizons revealed that the soil horizons consisted of kaolinite, illite and chrysotile with significant amount of opal-CT. Samples from Maddhapara, Bogra, and Nachole contain kaolinite, illite, quartz and opal-CT, and the samples from Kantabari contain chrysotile instead of kaolinite. Clay mineral compositions of different soil horizons indicated two different types of clay assemblages, viz. (a) illite-kaolinite and (b) illite-chrysotile. In the village of Kantabari, illite-chrysotile clay mineral assemblage indicate that soil horizons were formed under low temperatures with alkaline and reducing conditions. However, other soil horizons of illite-kaolinite clay mineral assemblage indicate that soils were possibly formed under humid, temperate and well-drained conditions. These two soil horizons were formed under different geochemical, geomorphological and climatic conditions from different parent materials. Scanning Electron Microscopy photographs showing the presence of glass shards and no opal-A were found using XRD, suggesting that the opal-A might not be a precursor to opal-CT in the red soil horizon of the study area. This opal-CT along with the general lack of fossils and presence of glass shards was indicative of a volcanogenic rather than biogenic origin for the Opal-CT in the study area, and X-ray fluorescence data reveals higher percentages of silica which is comparable to the Toba Ash of Toba Caldera, Indonesia of about 75,000 B.P.

Continuity and change in the lithic industries of the Jurreru Valley, India, before and after the Toba eruption

Lithic assemblage variability is synthesized and discussed for seven open sites and one rockshelter from the Jurreru Valley in the Kurnool district of southern India. The sites span the last c.77,000 years and provide an invaluable record of cultural change spanning the Toba Super-eruption, 74 thousand years ago (ka), as well as the transition to the microlithic. Lithic evidence documents long-term continuities before and after the eruption that indicates the Toba eruption had a minimal impact on the underlying system of flake production in the valley. The analysis also indicates that many cores from above and below the Toba ash are technologically extremely similar to those from early modern human sites in sub-Saharan Africa, southeast Asia and Australia, suggesting modern humans may have entered India before the Toba eruption as part of an early eastward dispersal from Africa.

A single southern exit of modern humans from Africa: Before or after Toba?

During the Late Pleistocene, anatomically modern humans (AMH) dispersed out of Africa. They first spread north with game, across the Sahara to the Levant during the Eemian interglacial (c.125 ka); and there is some recent evidence they may also have spread via Arabia to the Far East at the same time. However, they failed to continue to Europe, then occupied by Neanderthals. The Sahara and Arabia then reverted to aridity, and AMH vanished from the fossil record after 92 ka, being later replaced in the Levant, again by Neanderthals. There is recent fragmentary evidence AMH may also have spread via Arabia to the Far East, but the archaeological record fades similarly, long before the Toba eruption. There is no evidence of surviving non-African DNA lineages, dating from anywhere near the Eemian, to contradict this narrative. Genetic evidence indicates that AMH successfully left Africa much later, as a single group, by the southern route to India. Since all non-African uniparental lineages date to this later exit, this appears to have been the only ultimately successful AMH exit. AMH reached the isolated Sahul continent at least by 48 ka and possibly by 60–50 ka. AMH only finally arrived in Europe from South Asia before 46 ka, probably linked to climatic amelioration during MIS-3.Dating the definitive exit without adequate fossil evidence relies on disputed genetic dates with wide confidence intervals. At the top end, independent genetic dates combined with ash-associated data from Malaysia and from India argue for a pre-Toba exit, although the consensus view is still largely post-Toba. Recent correction for non-linearity due to purifying selection and recalibration of the mtDNA clock has improved confidence in genetic dating, but reduced the age of the main exit lineage (L3, which effectively embodies its maximum estimate) to just below that of Toba (71.6 ka), although relevant 95% Confidence Intervals (CI: 57.1–86.6 ka) still include the Toba event. This weakening of the genetic argument puts more pressure on the archaeological evidence associated with Toba ash and the need for diagnostic, well-dated fossil data between 90–70 ka.

Environmental impact of the 73 ka Toba super-eruption in South Asia

The cooling effects of historic volcanic eruptions on world climate are well known but the impacts of even bigger prehistoric eruptions are still shrouded in mystery. The eruption of Toba volcano in northern Sumatra some 73,000 years ago was the largest explosive eruption of the past two million years, with a Volcanic Explosivity Index of magnitude 8, but its impact on climate has been controversial. In order to resolve this issue, we have analysed pollen from a marine core in the Bay of Bengal with stratified Toba ash, and the carbon isotopic composition of soil carbonates directly above and below the ash in three sites on a 400 km transect across central India. Pollen evidence shows that the eruption was followed by initial cooling and prolonged desiccation, reflected in a decline in tree cover in India and the adjacent region. Carbon isotopes show that C 3 forest was replaced by wooded to open C 4 grassland in central India. Our results demonstrate that the Toba eruption caused climatic cooling and prolonged deforestation in South Asia, and challenge claims of minimal impact on tropical ecosystems and human populations.

Tropical rainforest vegetation, climate and sea level during the Pleistocene in Kerala, India

The southwestern Ghats region of the Indian Peninsula is unique for its extant endemic rainforest flora supported by high rainfall throughout the year. The record of tropical rainforest corresponding to the dynamic series of Pleistocene interglacial/glacial cycles is poorly known from peninsular India. This communication discusses the palynological study of organic matter (OM) deposits (>40 ka BP) in two well sections (Chaganachery, Kerala) from the Indian Peninsula (west coast). A rich archive of tropical rainforest pollen/spores and marine dinoflagellate cysts indicates anoxic fluvio-marine/estuarine depositional environments during warmer climates with an intensified Asian monsoon. The geochemical fingerprinting of glass shards indicates the presence of Youngest Toba ash of ∼74 ka from northern Sumatra, and therefore establishes a time-controlled stratigraphy. Thus, the depositional time period of the OM is related to the sea level highstand of Marine Isotopic Stage 5.1 (∼80 ka) which was the host to the YTT shards. The Late Quaternary pollen/spores diversity suggests that the modern climatic conditions in the southwestern Ghats have facilitated the conservation of moist evergreen rainforest and dry/moist deciduous forest. The pollen grains show its lineage with the extant flora and some of the fossil pollen recorded during the mesic Tertiary period from the Indian peninsula. Thus, it appears that the tropical rainforest survived here as ‘Plant Refugia’ in xeric (glacial) Quaternary periods, perhaps as riparian vegetation, and was rejuvenated during the Holocene as modern extant flora.

Tools in the Toba Ash Tuff

Tools in the Toba Ash Tuff

Cultural continuity and its implications on human evolution: A study from eastern Indian

Evidence of human evolution in India is mainly limited to cultural remains. Despite lack of proper absolute chronology a developmental pattern is established. Present work focuses on a specific region in the state of Orissa, located on eastern plateau region. So far no human fossil remain has been found from this area but there is enough cultural evidence to postulate evolutionary sequence. The earliest cultural remain, rich in Acheulian tradition, is found from the lower gravel bed, dated c. 0.3 myr B.P. on the basis of Toba ash. Then onward cultural evidences are found constantly from subsequent beds. Size diminution and refinement of technology is the hallmark for progress. Celts and polishing grinding technology is generally considered as the final phase of Stone Age technology. Findings from the region indicate continuation of the Stone Age tradition for a long time even into the recent past. The earliest metal finding is brass. This alloy is not only persisting in the region but even the technology of making brass objects is the same today. The tribal communities, the indigenous people living in the area, bear a legacy of behavioural strategy for survival. It appears that in the areas, life continued without a break from prehistory to present day in a processual manner. A similar situation is found in Africa, where as a result of comprehensive work the process of continuity is properly understood. In India, lack of absolute dates is the major hindrance for this kind of work. An attempt is made here to understand the behaviour, ecology and other related factors responsible for cultural continuity in the studied area.

Discovery of the Toba Ash ( c. 70 ka) in a high-resolution core recovering millennial monsoonal variability off Pakistan

Abstract A discrete Toba Ash layer in the northeastern Arabian Sea was detected near the base of a 20.2 m long piston core (289KL) recovered from the oxygen minimum zone off the Indus delta. In addition to the Toba Ash, we discovered two highly disseminated, vitreous, rhyolitic ‘ash layers’ in two annually laminated box cores: a ‘Younger Ash’ (about ad 1885–1900), and an ‘Older Ash’ (about ad 1815–1830). The glass shards were probably derived from eruptions of Indonesian volcanoes, although it was not possible to correlate these two ashes with well-known historical eruptions. We discuss source, transport and deposition of distal ash-fall layers in the Arabian Sea, which are derived from violent ultra-Plinian eruptions on the Indonesian volcanic archipelago, as well as their use for palaeoclimatic correlation. Core 289KL has a complete, high-resolution stratigraphic record of the past 75 ka with 21 interstadials (IS) or Dansgaard-Oeschger (D-O) cycles and equivalents of Heinrich events H1–H6. The high-frequency record of this core shows rapid climate oscillations with periods around 1.5 ka and can be tuned precisely to the δ 18 O record of a Bay of Bengal core and to the GISP-2 ice core from Greenland. The Toba event (70 ± 4 ka bp ), which is well documented in the Arabian Sea and Bay of Bengal records at the end of IS-20, as well as in the Greenland ice, is an excellent stratigraphic marker horizon to validate this correlation. The apparent synchronous appearance of the various D-O oscillations and Heinrich events, which has been documented for many northern hemisphere localities, can be explained only by fairly rapid atmospheric circulation changes. Changes in the intensity of the Indian summer monsoon are tightly coupled with suborbital climate oscillations in the northern hemisphere via atmospheric moisture and heat circulation.

Author Index

Volcanic glasses with minor mafic mineral fragments, such as biotite and hornblende, found in deep-sea sediments of the South China Sea Basin (SCSB) have been clearly identified as eruptive products of the Youngest Toba Tuff (YTT), northern Sumatra, Indonesia. The tephra layer occurs between marine oxygen isotopic event 5.1 (79.3 ka) and event 4.22 (64.1 ka), with an interpolated age of 74.0 ka, which is in good consistence with previous radiometric dating (73–75 ka) and ice-core dating (71±5 ka) of the YTT. The tephra consists predominantly of bubble-wall shards with minor elongated vesicles of pumice fragments. Geochemical characteristics of the tephra, such as high total alkali content, high 87Sr/86Sr ratio and uniformity of their compositions, all suggest that the recovered tephra is of the Youngest Toba Tuff. This finding supports an extended dispersal of coarse (>63 μm) glass shards over 1500 km northeast of the Toba caldera, a direction opposite to what previously conceived. While providing a better documentation of the distribution extent of the Toba ash, this report points to the need to re-estimating the eruptive volume of the YTT and re-evaluating its environmental impact.

Toba ash layers in the South China Sea: Evidence of contrasting wind directions during eruption ca. 74 ka: Comment and Reply

Toba ash layers in the South China Sea: Evidence of contrasting wind directions during eruption ca. 74 ka: Comment and Reply

Newly discovered eastern dispersal of the youngest Toba Tuff

Volcanic glasses with minor mafic mineral fragments, such as biotite and hornblende, found in deep-sea sediments of the South China Sea Basin (SCSB) have been clearly identified as eruptive products of the Youngest Toba Tuff (YTT), northern Sumatra, Indonesia. The tephra layer occurs between marine oxygen isotopic event 5.1 (79.3 ka) and event 4.22 (64.1 ka), with an interpolated age of 74.0 ka, which is in good consistence with previous radiometric dating (73‐75 ka) and ice-core dating (71 ^ 5 ka) of the YTT. The tephra consists predominantly of bubble-wall shards with minor elongated vesicles of pumice fragments. Geochemical characteristics of the tephra, such as high total alkali content, high 87 Sr/ 86 Sr ratio and uniformity of their compositions, all suggest that the recovered tephra is of the Youngest Toba Tuff. This finding supports an extended dispersal of coarse (.63 mm) glass shards over 1500 km northeast of the Toba caldera, a direction opposite to what previously conceived. While providing a better documentation of the distribution extent of the Toba ash, this report points to the need to reestimating the eruptive volume of the YTT and re-evaluating its environmental impact. q 2000 Elsevier Science B.V. All rights reserved.

Toba ash layers in the South China Sea: Evidence of contrasting wind directions during eruption ca. 74 ka

Two cores from the southern South China Sea contain discrete ash layers that mainly consist of rhyolithic glass shards. On the basis of the SPECMAP time scale, the ash layers were dated to ca. 74 ka, the age of the youngest Toba eruption in northern Sumatra. This link is supported by the chemical composition of the glass, which is distinct from volcanic glass supplied from the Philippines and the northern South China Sea, but is almost identical with the chemistry of the Toba ash. The youngest Toba ash layers in the South China Sea expand the previously known ash-fall zone over more than 1800 km to the east. The dispersal of ashes from Sumatra in both western and eastern directions indicates two contrasting wind directions and suggests that (1) the Toba eruption probably happened during the Southeast Asian summer monsoon season, and (2) the volume of erupted magma was larger than previously interpreted.