Global Chronology Research Articles

Integration of channel meander abandonment age uncertainty into a stochastic channelized system reconstruction method

The logic of sedimentary channelized systems is only partly preserved in the depositional record. We propose a new method to reconstruct 3D channelized systems from incomplete observations made on surface or subsurface images that integrates the uncertainty on meander abandonment chronology. Starting with the youngest channel path observed and the abandoned loops in the meander belt, the method generates local relative chronologies using cross-cutting analysis. It thus proposes a possible global chronology of channel meander abandonments by going back in time while updating the system configuration. This global chronology is obtained through a stochastic procedure that orders the youngest abandoned meanders with regard to their position and orientation relative to the current channel path. Ordered abandoned meanders are then integrated in the main channel path during the reverse migration process so that the global stochastic ordering is made at each time step of the migration algorithm consistently with the updated channel belt. The proposed approach is parameterized by the spatio-temporal density of meander cutoff along the channel belt, which can be inferred from analog databases. The application of our tool on a seismic stratal slice of the McMurray Formation in Canada provides various possible global chronologies of the abandoned meanders. We analyze the variability of these chronologies and highlight its impact on the various possible subsurface 3D global architectures of the paleo-system and on the associated subsurface heterogeneity.

Re-imagining the Empire of Japan through Japanese Schoolboy Uniforms

Japanese kimono and the Japanese schoolboy uniform continue to interact with, and interrogate, global fashions as contemporary designers continue to call on the tropes of ‘military chic’ (Tonchi) and Japanese-inspired clothing (Kawamura).

Evolution of an Alpine fluvioglacial system at the LGM decay: The Cormor megafan (NE Italy)

The dramatic climatic and environmental changes that occurred at the end of the last glaciation led to the formation of landforms (e.g., moraines, fluvial ridges, and alluvial terraces) that strongly characterize the landscape in the alluvial plains facing the Alps. This also occurred with the Tagliamento glacier, which built a large LGM moraine amphitheatre in the piedmont sector of the southeastern Alps and fed fluvioglacial systems in the Friulian plain (NE Italy). The Cormor stream was one of the main glacial outwashes and formed an alluvial megafan during the peak of the LGM. At the decline of the LGM, the active belt narrowed and was subsequently abandoned. Since the Lateglacial the Cormor system has been an intermittent stream with limited activity. This sequence of events led to the preservation of large LGM surfaces, which enables their investigation, along with correlatable moraine ridges. The study of megafan depositional phases allows us to precisely constrain the chronology of glacial withdrawal at the end of the LGM, which is difficult in large sectors of the southern Alps.The geomorphological and geological study of the Cormor megafan was realized through the use of remote sensing, DEM analysis, field survey, stratigraphic boreholes, and radiocarbon dating. During the peak glaciation of the LGM, the Cormor experienced widespread aggradation with gravel deposition up to 15–25km from the megafan apex, while the distal sector was dominated by fine-grained sediments. At the end of the LGM the Cormor stream incised the apical portion of its megafan, funnelling the sedimentary discharge and experiencing a limited aggradation in the distal sector with the formation of a progradational lobe. This deposition buried some swampy areas, sealing peaty and organic-rich clayey horizons with 2–4m of sediments. The top of these layers is radiocarbon dated at 22.0–19.5kacal BP and indirectly constrains the chronology of several recessional moraines that formed within the glacial amphitheatre.After this depositional phase, the Cormor megafan was deactivated because of water and sediment discharge concentration of the Tagliamento catchment in the Tagliamento River. This study demonstrates the possibility to reconstruct the timing of the decline of the Tagliamento moraine amphitheatre by studying the distal portion of the related outwash plain. Moreover, new geochronological dating allows chronological comparison of the glacial withdrawal in the eastern sector of the Southern Alps with the global chronology. The results suggest that we can apply this approach also in the distal part of the other alluvial megafans formed by Alpine glacial outwashes in the central part of the Po plain where radiocarbon chronology is almost lacking.

Global Chronology of Conflict

Global Chronology of Conflict

Sources: A Global Chronology of Conflict: From the Ancient World to the Modern Middle East

Sources: A Global Chronology of Conflict: From the Ancient World to the Modern Middle East

A Global chronology of conflict: from the ancient world to the modern Middle East

A Global chronology of conflict: from the ancient world to the modern Middle East

Ice Ages and the mitochondrial DNA chronology of human dispersals: a review.

Modern DNA, in particular maternally inherited mitochondrial DNA (mtDNA), is now routinely used to trace ancient human migration routes and to obtain absolute dates for genetic prehistory. The errors on absolute genetic dates are often large (50% or more) and depend partly on the inherent evolutionary signal in the DNA data, and partly on our imperfect knowledge of the DNA mutation rate. Despite their imprecision, the genetic dates do provide an independent, consistent and global chronology linking living humans with their ancestors. Combining this chronology with archaeological and climatological data, most of our own mtDNA studies during the past decade strongly imply a major role for palaeoclimate in determining conditions for prehistoric migrations and demographic expansions. This paper summarizes our interpretation of the genetic findings, covering the initial and modest spread of humans within Africa more than 100 ka, the striking re-expansion within Africa 60-80 ka, leading ultimately to the out-of-Africa migration of a single, small group which settled in Australia, Eurasia and America during windows of opportunity at least partly dictated by fluctuations in sea-levels and climatic conditions.

Volcanic aerosol records and tephrochronology of the Summit, Greenland, ice cores

The recently collected Greenland Ice Sheet Project 2 (GISP2) and Greenland Ice Core Project ice cores from Summit, Greenland, provide lengthy and highly resolved records of the deposition of both the aerosol (H2SO4) and silicate (tephra) components of past volcanism. Both types of data are very beneficial in developing the hemispheric to global chronology of explosive volcanism and evaluating the entire volcanism‐climate system. The continuous time series of volcanic SO42− for the last 110,000 years show a strong relationship between periods of increased volcanism and periods of climatic change. The greatest number of volcanic SO42− signals, many of very high magnitude, occur during and after the final stages of deglaciation (6000–17,000 years ago), possibly reflecting the increased crustal stresses that occur with changing volumes of continental ice sheets and with the subsequent changes in the volume of water in ocean basins (sea level change). The increase in the number of volcanic SO42− signals at 27,000–36,000 and 79,000–85,000 years ago may be related to initial ice sheet growth prior to the glacial maximum and prior to the beginning of the last period of glaciation, respectively. A comparison of the electrical conductivity of the GISP2 core with that of the volcanic SO42− record for the Holocene indicates that only about half of the larger volcanic signals are coincident in the two records. Other volcanic acids besides H2SO4 and other SO42− sources can complicate the comparisons, although the threshold level picked to make such comparisons is especially critical. Tephra has been found in both cores with a composition similar to that originating from the Vatnaöldur eruption that produced the Settlement Layer in Iceland (mid‐A.D. 870s), from the Icelandic eruption that produced the Saksunarvatn ash (∼10,300 years ago), and from the Icelandic eruption(s) that produced the Z2 ash zone in North Atlantic marine cores (∼52,700 years ago). The presence of these layers provides absolute time lines for correlation between the two cores and for correlation with proxy records from marine sediment cores and terrestrial deposits containing these same tephras. The presence of both rhyolitic and basaltic shards in the Z2 ash in theGISP2 core and the composition of the basaltic grains lend support to multiple Icelandic sources (Torfajökull area and Katla) for the Z2 layer. Deposition of the Z2 layer occurs at the beginning of a stadial event, further reflecting the possibility of a volcanic triggering by the effects of changing climatic conditions.

Stratigraphic placement of the Santonian-Campanian boundary (Upper Cretaceous) in the North American Gulf Coastal Plain and Western Interior, with implications to global geochronology

Recent micro- and macropaleontological research in the northern Aquitaine Basin of France, the stratotypic area for the Upper Cretaceous Santonian and Campanian Stages, was used to resolve a long-standing discrepancy in the stratigraphic position of the Santonian-Campanian boundary in east-central Texas as based upon zonations of planktonic foraminifers versus ammonites. On the basis of the presence in Texas of species of ammonites restricted to the lower reaches of the basal Campanian Placenticeras bidorsatum Zone of the Aquitaine Basin, the Santonian-Campanian boundary in Texas is significantly lower than has generally been considered by micropaleontologists. Specifically, it is within the foraminifer-based Globotruncana (= Marginotruncana ) concavata Zone ( sensu lato ). Such placement involves middle reaches of the type Austin Chalk, perhaps within the Dessau Chalk Member. An assumption that underlies the following conclusions is that the boundaries of the G. concavata Zone as recognized in European Tethys, the Atlantic and Caribbean basins, and North American Gulf Coast represent approximately synchronous stratigraphic levels. The following represent additional conclusions of pertinence to global chronology of the Cretaceous. (1) Rather than being younger than the Globotruncana concavata Zone, the Placenticeras bidorsatum Zone should be thought of as being contemporary with at least the younger half of the G. concavata (species total range) Zone. (2) Most of the Merchantville and Magothy Formations on the Atlantic seaboard of New Jersey and Delaware were deposited during early Campanian time, rather than principally during the Santonian. (3) The traditional placement of the Santonian-Campanian boundary in the Western Interior of North America slightly below the zone of Scaphites hippocrepis I is essentially correct. (4) The chronology of the Niobrara Formation of the North American Western Interior as based upon planktonic foraminifers is shown to be in serious error; specifically, it has been considered much too young. (5) Paleomagnetically sampled parts of the Niobrara Formation probably correlate with upper reaches of the “Cretaceous Long Normal Interval”, below magnetochron 33R. (6) Although the Santonian Stage surely represents a surprisingly brief interval of earth history, the Coniacian-Santonian boundary probably should be placed below the G. concavata Zone. (7) The Santonian-Campanian boundary slightly post-dates initiation of the last general Cretaceous regression of the North American Western Interior Seaway. (8) The beginning of the North American Aquilan Land Mammal “Age” represents earliest Campanian time. (9) Rather than representing an earliest Campanian geomagnetic event, the temporal span of global magnetochron 33R equates with approximately the second quarter of the total duration of the Campanian.

Regards sur le monde agricole : les archives filmiques

The film records, in spite of their scattering, of their insufficient classification, and of interpretation problems, are a first class source for the knowledge of rural world. They « enable us to see » the agricultural techniques, practices, rituals, environment of the traditional peasant society between the two -world wars, and they provide us with the 1950-1980 decades. That's what allows monographs and thematic studies according to an historical prospect. Similarly, one can analyze, through the films, the too often stereotyped image of the rural world, which expresses the feelings and the collective perception of the comprehensive society, as well as determine the ideological message these records are bearing. The « ruralists » cannot avoid to systematically compare the global chronology to the film one.

Holocene Sea-Level History: Case Study of the Statistical Evaluation of14C Dates

The limits of the statistical evaluation of14C dates by histograms are discussed. The method of the attempt to establish a global chronology of the short-term eustatic sea-level changes during the Holocene is examined as well as its correlation with the precisely determined Suess wiggles.