A Significant middle Pleistocene tephra deposit preserved in the caves of Mulu, Borneo

2012 ◽  
Vol 77 (3) ◽  
pp. 335-343 ◽  
Author(s):  
Joyce Lundberg ◽  
Donald A. McFarlane
Keyword(s):  
Grain Size ◽  
Isotopic Ratio ◽  
The Philippines ◽  
Plinian Eruption ◽  
Middle Pleistocene ◽  
Fall Deposit ◽  
Potential Source ◽  
Tephra Deposit ◽  
Potential Sources ◽  
Ratio Limit

A distinctive white sediment in the caves of Mulu, Sarawak, Borneo is a well-preserved tephra, representing a fluvially transported surface air-fall deposit, re-deposited inside the caves. We show that the tephra is not the Younger Toba Tephra, formerly considered as most likely. The shards are rod-shaped with elongate tubular vesicles; the largest grains ~ 170 μm in length; of rhyolitic composition; and 87Sr/86Sr ratio of 0.70426 ± 0.00001. U–Th dating of associated calcites suggest that the tephra was deposited before 125 ± 4 ka, and probably before 156 ± 2 ka. Grain size and distance from closest potential source suggests an eruption of VEI 7. Prevailing winds, grain size, thickness of deposit, location of potential sources, and Sr isotopic ratio limit the source to the Philippines. Comparisons with the literature give the best match geochemically with layer 1822 from Ku et al. (2009a), dated by ocean core stratigraphy to 189 ka. This tephra represents a rare terrestrial repository indicating a very substantial Plinian/Ultra-Plinian eruption that covered the Mulu region of Borneo with ash, a region that rarely receives tephra from even the largest known eruptions in the vicinity. It likely will be a valuable chronostratigraphic marker for sedimentary, palaeontological and archaeological studies.

scholarly journals Changes in Paleovegetation and Paleoclimate in China Since the Late Middle Pleistocene: A Case Study of the Dajiuhu Basin

2021 ◽  
Vol 13 (9) ◽  
pp. 4848
Author(s):  
Liwei Wu ◽  
Xinling Li ◽  
Qinghai Xu ◽  
Manyue Li ◽  
Qiufeng Zheng ◽  
...  
Keyword(s):  
Grain Size ◽  
Asian Monsoon ◽  
East Asian Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Central China ◽  
Middle Pleistocene ◽  
Pollen Record ◽  
The Difference ◽  
Late Middle Pleistocene

The East Asian monsoon system is an important part of global atmospheric circulation; however, records of the East Asian monsoon from different regions exhibit different evolutionary rhythms. Here, we show a high-resolution record of grain size and pollen data from a lacustrine sediment core of Dajiuhu Lake in Shennongjia, Hubei Province, China, in order to reconstruct the paleovegetation and paleoeclimate evolution of the Dajiuhu Basin since the late Middle Pleistocene (~237.9 ka to the present). The results show that grain size and pollen record of the core DJH-2 are consistent with the δ18O record of stalagmites from Sanbao Cave in the same area, which is closely related to the changes of insolation at the precessional (~20-kyr) scale in the Northern Hemisphere. This is different from the records of the Asian summer monsoon recorded in the Loess Plateau of North China, which exhibited dominant 100-kyr change cyclicities. We suggest that the difference between paleoclimatic records from North and South China is closely related to the east–west-oriented mountain ranges of the Qinling Mountains in central China that blocked weakened East Asia summer monsoons across the mountains during glacial periods.

La production de limon sur des terrasses de cryoplanation dans les monts Richardson, Canada

1999 ◽  
Vol 36 (10) ◽  
pp. 1645-1654 ◽  
Author(s):  
I Lamirande ◽  
B Lauriol ◽  
A E Lalonde ◽  
I D Clark
Keyword(s):  
Grain Size ◽  
Size Fraction ◽  
Runoff Water ◽  
Chemical Action ◽  
Intergranular Porosity ◽  
Potential Source ◽  
Petrographic Analyses ◽  
Glacial Time ◽  
Richardson Mountains ◽  
Quartz Grains

The production of silt on cryoplanation terraces in the Richardson Mountains was documented by a sedimentological study. Geochemical, grain-size, and petrographic analyses of the Jurassic Bug Creek sandstone were done. Results show that in the unaltered rock the detrital quartz grains are solidly held by a siliceous cement. In the altered and strongly altered sandstone, there is a marked increase in intergranular porosity and fracturing of the grains. The disaggregation and weathering of the sandstone releases mainly material in the silt-size fraction, with lesser amounts of sand and clay. This material covers the tread of the terraces and constitutes a potential source of loess in glacial time. Runoff water has a PCO2 value two orders of magnitude greater than the atmosphere yet is weakly mineralized, with only amorphous silica approaching saturation. However, the weathering of sandstones is probably accelerated by the chemical action of water which, by attacking the cement that forms the diagenetic overgrowth of the quartz grains, facilitates their release.

The use of diets containing high levels of copra meal for growing/finishing pigs

1997 ◽  
Vol 1987 ◽  
pp. 97-97
Author(s):  
P.J. Thorne ◽  
J. Wiseman ◽  
D.J.A. Cole
Keyword(s):  
Coconut Oil ◽  
Oil Industry ◽  
The Philippines ◽  
Finishing Pigs ◽  
Poor Growth ◽  
Copra Meal ◽  
Potential Source ◽  
Tropical Conditions ◽  
The University ◽  
The Tropics

Copra meal is a by-product of the coconut oil industry and is a potential source of protein and energy in the diets of pigs and poultry in the tropics. However, previous studies with pigs have suggested that its use may be limited because of poor growth performance associated with levels of inclusion above 300 g/kg (Creswell and Brooks, 1971). The experiment reported here and conducted under tropical conditions at the University of the Philippines at Los Banos was designed to study possible ways of feeding copra meal at levels of inclusion greater than 300 g/kg in the diets of pigs while maintaining acceptable animal performance.

scholarly journals The Orange Tuff: a Late Pleistocene tephra-fall deposit emplaced by a VEI 5 silicic Plinian eruption in West Java, Indonesia

2019 ◽  
Vol 81 (6) ◽  
Author(s):  
Christopher J. Harpel ◽  
Kushendratno ◽  
James Stimac ◽  
Cecilia F. Avendaño Rodríguez de Harpel ◽  
Sofyan Primulyana
Keyword(s):  
Late Pleistocene ◽  
Plinian Eruption ◽  
Fall Deposit ◽  
West Java ◽  
Tephra Fall

Quantitative reconstruction of landscape dynamics and tectonics from sediment calibre and architecture: an example from the Kerinitis megadelta, Gulf of Corinth, Greece

2020 ◽  
Author(s):  
Daniel Hobley ◽  
Alexander Whittaker
Keyword(s):  
Grain Size ◽  
Middle Pleistocene ◽  
Normal Faults ◽  
Sudden Increase ◽  
Level Control ◽  
Data Set ◽  
Accommodation Space ◽  
Gulf Of Corinth ◽  
Climatic Environment ◽  
Climatic History

<p>In tectonically active landscapes, fault movement drives both the creation of accommodation space (i.e., basins), and the production of topography on which geomorphic processes act (i.e., mountains). The action of fluvial processes on those mountains will route eroded sediment into the basins; in many extensional mountain belts, this leads to the deposition of coarse alluvial fans or Gilbert deltas in the hanging-walls of normal faults as they slip and create accommodation space. The stratigraphic architecture and sedimentary characteristics of such deposits clearly respond to and thus in principle can record the tectono-climatic environment controlling the system. This implies that key stratigraphic variables, such as grain size and unit thicknesses, can be quantitatively inverted to recover a tectono-climatic history. However, confounding variables also active in erosional-depositional systems (e.g., far-field base level control, stochastic processes, signal degradation during transport) may complicate attempts to decode this archive and may buffer or shred tectono-climatic signals before they are preserved.</p><p>The well-exposed early to middle Pleistocene deltaic stratigraphy of the Corinth Rift, central Greece, provides a rare opportunity to test these ideas quantitatively. Here, we present a preliminary data set attempting to decode the geomorphic and hence tectono-climatic history of a key section of the rift directly from the grain size and architecture of a very large (~500 m thick), fault controlled, and now uplifted Gilbert delta in the Kerinitis valley, located on the southern margin of the Gulf of Corinth. We used a series of high-resolution drone surveys to obtain 27 vertical transects through the incised delta, from which detailed grain size and sediment thickness data were obtained from photogrammetric analyses (~10,000 images). Our data enabled us to produce a highly detailed correlation of stratal horizons within the deltaic package, from which we were able to describe the evolution of grain size trends both downstream and through the ca. 800 ky lifespan of the delta. We are able to resolve a marked acceleration of the driving fault from the delta stratigraphy itself, which is recorded in a sudden increase in downstream fining rate, driven by more rapid extraction of sediment from the river supplying material to the delta. The timing of this increase correlates with independent constraints from stratigraphic form on the onset of “rift climax” in this delta. Post fault acceleration, we demonstrate that the fining rates begin to fall back, consistent with transient response to tectonic perturbation in the upstream catchment and with a wave of incision sweeping up through the terrestrial system. Our results demonstrate that sophisticated insights into fault evolution can be drawn from deltaic stratigraphy, and emphasise the importance of transient landscape response in creating rift zone sedimentary archives.</p>

Generation of a Stochastic Seismic Event Set Based on a New Seismicity Model in China’s Earthquake Catastrophe Model

2021 ◽  
Author(s):  
Weijin Xu ◽  
Mengtan Gao ◽  
Huiqiang Zuo
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Seismic Event ◽  
Hazard Analysis ◽  
Source Model ◽  
Seismic Events ◽  
Catastrophe Model ◽  
Potential Source ◽  
Potential Sources ◽  
Seismicity Model

Abstract Earthquakes are among the most devastating natural disasters in China, causing serious casualties and property losses. To effectively reduce catastrophic risk, it is important to establish an earthquake catastrophe insurance system based on the earthquake catastrophe model, of which seismic hazard analysis is a main module. Probabilistic seismic-hazard analysis uses the potential source model, seismicity model, and ground-motion attenuation model, as well as the probability method to obtain the seismic hazard value of a given point. However, because the influence of a single seismic event is required when the earthquake catastrophe model is used for risk analysis, a series of single events needs to be generated according to the potential source model so as to calculate the influence of each event on the given point. In this study, based on the seismicity model (potential sources and their seismicity parameters) used in compiling the fifth generation of Seismic Ground Motion Parameter Zoning Map of China, we use the Monte Carlo method to simulate seismic events conforming to temporal, spatial, and intensity distribution of China’s seismic activities. In the simulation process, we follow the Poisson distribution in occurrence time and the Gutenberg–Richter law in magnitude distribution, and we use potential sources and earthquake occurrence rates to describe spatial distribution. The simulated seismic events include the following parameters: date (year, month, and day), location (longitude and latitude), depth, magnitude, and attitude of seismogenic faults. The simulated seismic event set can support earthquake risk analysis in the earthquake catastrophe model and has been applied in the earthquake catastrophe model of China.

High-resolution seismic geomorphology and stratigraphy of a tunnel valley confined ice-margin fan (Elsterian glaciation, Southern North Sea)

2016 ◽  
Vol 4 (4) ◽  
pp. T461-T483 ◽  
Author(s):  
Antonio Benvenuti ◽  
Andrea Moscariello
Keyword(s):  
Grain Size ◽  
High Resolution ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
North Sea ◽  
Large Scale ◽  
Scale Up ◽  
Ice Sheet ◽  
Middle Pleistocene ◽  
Southern North Sea

The deep Middle Pleistocene subglacial incisions of the Southern North Sea (SNS) are commonly infilled by northward gently dipping clinoforms oriented toward the former ice-sheet core. We have focused on the terminal sector of the largest tunnel valley (TV) of the SNS and offer the first high-resolution reconstruction of the geomorphology and stratigraphy of the infill of the glacial incision, as well as the detailed geomorphology of the incision to better understand the genetic mechanisms of these uncommon but peculiar large-scale (up to 13 km in length) bedforms. For this study, high-resolution 3D seismic data, the grain-size distribution from ditch cutting samples, and the gamma-ray wireline log of borehole K14-12 are used. The TV formed in the subglacial environment by steady state flows in a time-transgressive fashion. Meltwater flow transports the eroded material southward and eventually deposits it at the ice-sheet margin, in the lightly grounded ice-sheet environment where the adverse slope forces the flow to wane. The process results in an elongated ice-margin fan made of clinoforms, whose grain-size distribution fines progressively southward, in the downstream direction. The formation and filling of the TV occurred during the retreat of the ice-sheet margin and cyclic fluctuations of the meltwater mass flow rate, which affected the internal stratigraphy and created an undulated top of the clinoforms’ unit. Sparsely distributed, horizontally layered units interpreted as distal proglacial lacustrine deposits filled depressions on the top of the clinoforms-bearing unit. The sequence was then sealed by a chaotic seismic-stratigraphic unit that probably belongs to postglacial times. The ice-sheet-oriented clinoforms were thus formed by sustained meltwater flow resulting from large-size Scandinavian and British convergent ice sheet flows in the freshwater environment of SNS developed between the complex ice margins and the topographic highs inherited from continental Europe.

Mollusk Record of Monsoon Variability during the L2–S2 Cycle in the Luochuan Loess Sequence, China

1999 ◽  
Vol 52 (3) ◽  
pp. 286-292 ◽  
Author(s):  
Denis-Didier Rousseau ◽  
Naiqin Wu
Keyword(s):  
Grain Size ◽  
Environmental Conditions ◽  
Middle Pleistocene ◽  
Northwestern Pacific ◽  
Ecological Groups ◽  
Proxy Data ◽  
Climate Conditions ◽  
Monsoon Variability ◽  
Temperature Requirements ◽  
Terrestrial Mollusks

Molluscan changes that occurred in China over the S2–L2 upper middle Pleistocene series may be caused by monsoon variation. Study of terrestrial mollusks from the loess sequence in Luochuan, gathered in ecological groups according to the moisture and temperature requirements of the identified species, indicates alternating strengthened summer and winter paleomonsoons between 130,000 and 244,000 yr. The four occurrences of species, currently distributed in S.E. China in the sequence, indicate that the climate conditions were warmer and wetter than today between about 242,000 and 233,000 yr, at about 210,000, 164,000, and 140,000 yr. The main occurrence of xerophilous taxa at about 180,000, 154,000, and 138,000 yr is interpreted as indicating a drier environment than today. Such suggestions are in agreement with other proxy data such as grain size distribution. Higher numbers of individuals in the different ecological groups from the S2–L2 sequence indicate more favorable general environmental conditions than in the youngest S1–L1. This may agree with an increase in the regional aridity, since 500,000 yr, deduced from the study of the eolian flux in the northwestern Pacific downwind from China.

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