Event layers in the Japanese Lake Suigetsu 'SG06' sediment core:Description, interpretation and climatic implications

Event layers in lake sediments are indicators of past extreme events, mostly the results of floods or earthquakes. Detailed characterisation of the layers allows the discrimination of the sedimentation processes involved, such as surface runoff, landslides or subaqueous slope failures. These processes can then be interpreted in terms of their triggering mechanisms. Here we present a 40 ka event layer chronology from Lake Suigetsu, Japan. The event layers were characterised using a multi-proxy approach, employing light microscopy and μXRF for microfacies analysis. The vast majority of event layers in Lake Suigetsu was produced by flood events (362 out of 369), allowing the construction of the first long-term, quantitative (with respect to recurrence) and well dated flood chronology from the region. The flood layer frequency shows a high variability over the last 40 ka, and it appears that extreme precipitation events were decoupled from the average long-term precipitation. For instance, the flood layer frequency is highest in the Glacial at around 25 ka BP, at which time Japan was experiencing a generally cold and dry climate. Other cold episodes, such as Heinrich Event 1 or the Late Glacial stadial, show a low flood layer frequency. Both observations together exclude a simple, straightforward relationship with average precipitation and temperature. We argue that, especially during Glacial times, changes in typhoon genesis/typhoon tracks are the most likely control on the flood layer frequency, rather than changes in the monsoon front or snow melts. Spectral analysis of the flood chronology revealed periodic variations on centennial and millennial time scales, with 220 yr, 450 yr and a 2000 yr cyclicity most pronounced. However, the flood layer frequency appears to have not only been influenced by climate changes, but also by changes in erosion rates due to, for instance, earthquakes

New 14C Determinations from Lake Suigetsu, Japan:12,000 to 0 Cal BP

Calibration is a fundamental stage of the radiocarbon (14C) dating process if one is to derive meaningful calendar ages from samples’ 14C measurements. For the first time, the IntCal09 calibration curve (Reimer et al. 2009) provided an internationally ratified calibration data set across almost the complete range (0 to 50,000 cal BP) of the 14C timescale. However, only the last 12,550 cal yr of this record are composed of terrestrial data, leaving approximately three quarters of the 14C timescale necessarily calibrated via less secure, marine records (incorporating assumptions pertaining to the temporally variable “marine reservoir effect”). The predominantly annually laminated (varved) sediment profile of Lake Suigetsu, central Japan, offers an ideal opportunity to derive an extended terrestrial record of atmospheric 14C across the entire range of the method, through pairing of 14C measurements of terrestrial plant macrofossil samples (extracted from the sediment) with the independent chronology provided through counting of its annual laminations. This paper presents new data (182 14C determinations) from the upper (largely non-varved) 15 m of the Lake Suigetsu (SG06) sediment strata. These measurements provide evidence of excellent coherence between the Suigetsu 14C data and the IntCal09 calibration curve across the last ~12,000 cal yr (i.e. the portion of IntCal based entirely on terrestrial data). Such agreement demonstrates that terrestrial plant material picked from the Lake Suigetsu sediment provides a reliable archive of atmospheric 14C, and therefore supports the site as being capable of providing a high-resolution extension to the “wholly terrestrial” (i.e. non-reservoir-corrected) calibration curve beyond its present 12,550 cal BP limit

Atlas of pollen, spores and further non-pollen palynomorphs recorded in the glacial-interglacial late Quaternary sediments of Lake Suigetsu, central Japan

Abstract not availableDieter Demske,Pavel E. Tarasov,Takeshi Nakagawa, Suigetsu 2006 Project Member

A re-analysis of the Lake Suigetsu terrestrial radiocarbon calibration dataset

Suigetsu 2006 Project Members: J.J. Taylor for the University of Adelaide.R.A. Staff, C. Bronk Ramsey, T. Nakagawa, Suigetsu 2006 Project Member

A standard sample method for controlling microfossil data precision: a proposal for higher data quality and greater opportunities for collaboration

Suigetsu 2006 Project Members: J. J. Taylor for the University of Adelaide.Abstract not availableTakeshi Nakagawa, Hiroyuki Kitagawa, Rebecca Payne, Pavel Tarasov, Dieter Demske, Suigetsu 2006 Project Member

Identification of the Changbaishan ‘Millennium’ (B-Tm) eruption deposit in the Lake Suigetsu (SG06) sedimentary archive, Japan: Synchronisation of hemispheric-wide palaeoclimate archives

The B-Tm tephra, dispersed during the highly explosive Changbaishan ‘Millennium’ eruption (ca. 940–950 CE) and a key marker layer within the Greenland ice cores, has now been identified in the Lake Suigetsu (SG06) sedimentary sequence, central Japan. The major element geochemistry of the volcanic glasses within this tephra layer are compared to a new glass dataset from the distal type-locality (Tomakomai Port, Hokkaido) and other published ‘Millennium’ eruption/B-Tm deposits, to verify this correlation. The discovery of the B-Tm tephra in the Lake Suigetsu record provides, to date, the most southerly identification of this ash and, crucially, the first direct tie-point between this high-resolution, mid-latitude palaeoclimate archive and the Greenland ice cores. These findings present significant encouragement for on-going research into the tephrostratigraphy of East Asia, focusing on the identification of widely-dispersed tephra layers which can facilitate the synchronisation of disparate palaeoclimate archives and thus enable the assessment of spatio-temporal variations in past climatic change

Identification and correlation of visible tephras in the Lake Suigetsu SG06 sedimentary archive, Japan: chronostratigraphic markers for synchronising of east Asian/west pacific palaeoclimatic records across the last 150 ka

The Lake Suigetsu SG06 sedimentary archive from Honshu Island, central Japan, provides a high-resolution palaeoenvironmental record, including a detailed record of explosive volcanism from Japan and South Korea. Thirty visible tephra are recorded within the 73 m-long SG06 core, which spans the last ∼150 ka. Here we describe and characterise these tephras based on major element glass composition, which is useful for the identification and correlation of these tephras and the age models of the records in which they are found. Utilising the large number of radiocarbon measurements (n > 600) from terrestrial plant macrofossils in the Lake Suigetsu SG06 record, we are able to provide precise and accurate ages for the tephras from eruptions within the last 50 ka. Glass compositional data of some of the largest eruptions from Japan (K-Ah, AT, Aso-4, Aso-A, Aso-D, and Ata; sampled at proximal outcrops) are also presented. These data show that the major element glass chemistry is distinctive for many of the visible SG06 tephra units, and allows some of the layers to be correlated to known eruptions from volcanoes in Japan and South Korea, namely K-Ah (SG06-0967), U-Oki (SG06-1288), AT (SG06-2650), Aso-4 (SG06-4963/SG06-4979), K-Tz (SG06-5181), Aso-ABCD (SG06-5287) and Ata (SG06-5181). The following ages were obtained for the SG06 tephra units: 3.966–4.064 cal. ka BP (95.4% probability range) for the SG06-0588 tephra, 10.242–10.329 cal. ka BP (95.4% probability range) for SG06-1293, 19.487 ± 112 SG062012 ka BP (2 σ) for SG06-1965, 28.425 ± 194 SG062012 ka BP (2 σ) for SG06-2504, 28.848 ± 196 SG062012 ka BP (2 σ) for SG06-2534, 29.765 ± 190 SG062012 ka BP (2 σ) for SG06-2601, 29.775 ± 191 SG062012 ka BP (2 σ) for SG06-2602, 43.713 ± 156 SG062012 ka BP (2 σ) for SG06-3485, 46.364 ± 202 SG062012 ka BP (2 σ) for SG06-3668, 49.974 ± 337 SG062012 ka BP (2 σ) for SG06-3912, 50.929 ± 378 SG062012 ka BP (2 σ) for SG06-3974, and improved ages for two of the most important tephra markers across Japan, the K-Ah (7.165–7.303 cal. ka BP at 95.4% probability range; SG06-0967) and AT tephra (30.009 ± 189 SG062012 ka BP at 2 σ; SG06-2650)