Southward Expansion Research Articles

Shallow structure of the eastern segment of the Mediterranean Ridge deduced from seismic and side-scan sonar data

The eastern Mediterranean Ridge reveals a peculiar feature called the “United Nations Rise”. It is notable for its complex morphology, interior structure, and mud volcanism. Its unusual structural–morphological characteristics are explained by its location at a junction of the western and eastern branches of the ridge and by the probable tectonic escape of accretionary prism sediments from the west. The geophysical data on the shallow structure of the eastern ridge branch showed some unusual structural trends, which could not be expected from the overall tectonic stress distribution. They are interpreted as resulting from the southward expansion of the Hellenic Arc.

Neanderthal skeleton from Tabun: U-series data by gamma-ray spectrometry

The Neanderthal hominid Tabun C1, found in Israel by Garrod & Bate, was attributed to either layer B or C of their stratigraphic sequence. We have used gamma-ray spectrometry to determine the230Th/234U and231Pa/235U ratios of two bones from this skeleton, the mandible and a femur. The ages calculated from these ratios depend on the uranium uptake history of the bones. Assuming a model of early U (EU) uptake the age of the Tabun C1 mandible is 34±5ka. The EU age of the femur is 19±2ka. The femur may have experienced continuous (linear) U uptake which would give an age of 33±4ka, in agreement with the mandible's EU age, but implies marked inhomogeneity in U uptake history at the site. These new age estimates for the skeleton suggest that it was younger than deposits of layer C. This apparent age is less than those of other Neanderthals found in Israel, and distinctly younger than the ages of the Skhul and Qafzeh burials. This suggests that Neanderthals did not necessarily coexist with the earliest modern humans in the region. All of the more complete Neanderthal fossils from Israel are now dated to the cool period of the last glacial cycle, suggesting that Neanderthals may have arrived in this region as a result of the southward expansion of their habitable range. The young age determined for the Tabun skeleton would suggest that Neanderthals survived as late in the Levant as they did in Europe.

Biome reconstruction from pollen and plant macrofossil data for Africa and the Arabian peninsula at 0 and 6000 years

Biome reconstruction from pollen and plant macrofossil data provides an objective method to reconstruct past vegetation. Biomes for Africa and the Arabian peninsula have been mapped for 6000 yearsbpand provide a new standard for the evaluation of simulated palaeovegetation distributions. A test using modern pollen data shows the robustness of the biomization method, which is able to predict the major vegetation types with a high confidence level. The application of the procedure to the 6000 years data set (pollen and plant macrofossil analyses) shows systematic differences from the present that are consistent with the numerous previous regional and continental interpretations, while providing a more extensive and more objective basis for such interpretations. Madagascar, eastern, southern and central Africa show only minor changes in terms of biomes, compared to present. Major changes in biome distributions occur north of 15°N, with steppe in many low‐elevation sites that are now desert, and temperate xerophytic woods/scrub and warm mixed forest in the Saharan mountains. These shifts in biome distributions imply significant changes in climate, especially precipitation, between 6000 years and present, reflecting a change in monsoon extent combined with a southward expansion of Mediterranean influence.

DISTRIBUTION OF THE LYNX IN THE FRENCH ALPS

Abstract The European lynx disappeared from the French Alps around the beginning of the 20th century. The recovery in France is due to the re-introduction in Switzerland between 1971 and 1976. From 1974 to 1994, there were 70 records. The first records were recorded in Chablais. More regular records were around the Aravis mountains. Over 20 years, a southward expansion of about 200 km has been observed but no continuous distribution area has been shown by the survey. Observations remained scattered, probably because of low observation effort in many areas. Different possibilities for connections with the Jura populations seemed to exist in the French Alps. Bauges, Chartreuse and even Saleve could have been reached by individuals originating from the Jura or from the northern Alps. If the presence of the lynx south of Grenoble in the Vercors and in the Hautes Alpes departement is confirmed, expansion of the population over the whole south-east of France would be possible.

Surface temperature in NW Europe during the Younger Dryas: AGCM simulation compared with temperature reconstructions

During the Younger Dryas (YD) the climate in NW Europe returned to near-glacial conditions. To improve our understanding of climate variability during this cold interval, we compare an AGCM simulation of this climate, performed with the ECHAM model, with temperature reconstructions for NW Europe based on geological and paleoecological records. Maps for the mean winter, summer and annual temperature are presented. The simulated winters are consistent with reconstructions in the northern part of the study area. A strong deviation is noted in Ireland and England, where the simulation is too warm by at least 10 °C. It appears that the N Atlantic was cooler than prescribed in the YD simulation, including a southward expansion of the sea-ice margin. The comparison for the summer shows a too warm continental Europe in the simulation. Supposedly, these anomalously warm conditions are caused by the AGCM’s response to the prescribed increased summer insolation. The region of maximum summer cooling is similar in both the simulation and reconstruction, i.e., S Sweden. We suggest that this is due to the local cooling effect of the Scandinavian ice sheet. Compared to the present climate a considerable increase of the annual temperature range is inferred, especially for regions close to the Atlantic Ocean.

Paleoclimatic implications of the presence of Clyomys (Rodentia, Echimyidae) in the Pleistocene of central Argentina

The presence of the Echimyidae Eumysopinae Clyomys in Ensenadan (Early-Middle Pleistocene) sediments cropping out northeast of Mar del Plata and south of Necochea (costal region of Buenos Aires province, Argentina) is reported. This is the first citation of Clyomys in Argentina and the first post-Pliocene record of echymids at this latitude. These remains represent a species closely related to the extant representatives of the genus, which live at least 1600 km north of the new localities. These fossils suggest that a southward expansion of the Brazilian fauna occurred during a warm and humid pulse in the Pleistocene.

‘Trouble Must Follow’: Australia's Ban on Iron Ore Exports to Japan in 1938

Despite the attention that has been given to the role of economic sanctions in Japan's decision to launch the Pacific war, Australia's decision to ban iron ore exports to Japan has been given little attention, even though this was one of the earliest economic sanctions imposed onimperial Japan in the 1930s. To a degree this neglect can be traced to a preoccupation with the actions and objectives of the great powers and a failure to consider the opportunities available to small nations to take significant initiatives. The following article traces the origins of the iron ore embargo back to 1934 when Essington Lewis, the Managing Director of the Broken Hill Proprietary Company Ltd (BHP), Australia's iron and steel monopoly, visited Japan and subsequently advocated the development of an Australian armaments industry to counter probable Japanese aggression in the Pacific. In Japan Lewis crossed paths with J. G. Latham, the Minister for External Affairs, who was leading the Australian government's Eastern Mission. Latham returned to Australia with conclusions that differed fundamentally from those of Lewis, who came up with a plan to take advantage of Japan's dependence on imports of iron ore and other iron products to finance investment in Australian armaments manufacturing. In explaining this outcome the article discusses interactions between a number of conflicts: between Latham and Lewis; between the British Treasury and the Foreign Office; and between the Japanese army and navy. In London the Treasury wanted to focus on the European theatre, while also holding down military spending in order to achieve balanced budgets. The Treasury believed that the way to best defend British commercial interests in Asia was to appease Japan. On the other hand, the Foreign Office was committed to the protection of British interests in the Far East by a more forceful diplomacy, although it was only willing to counten-ance behavior short of military action. Consistent with Latham's recommendations to his government, the emerging consensus in London was that while a settlement in China would help to safeguard British interests there, as long as the Japanese were bound up in their war in China they were less likely to attack British colonies in Southeast Asia and the Pacific. In 1936 this orientation was challenged by a shift in the balance of power in Tokyo away from the army and in favor of the navy. Although priority continued to be placed on winning the war in China and guarding against an attack from the Soviet Union, now the navy's plan for southward expansion was given more careful consideration and credibility.

Strain patterns within the late Variscan granitic dome of Velay, French Massif Central

The Velay granites are intruded as a late Variscan dome in the French Massif Central. Strain patterns within the Velay granites reflect the geometry and kinematics of late Carboniferous deformation, at the site of final emplacement. The internal deformation developed during granitic magmatism is not homogeneously distributed. From inner to outer zones increasing deformation is marked by changes from high-temperature foliations to S- C orthogneisses. Strain concentration at the margins reflects a strength contrast due to cooling and subsequent magma hardening. According to the internal strain field two zones can be distinguished in the Velay dome: (i) a central and southern zone where concentric patterns indicate a southward expansion of granites; and (ii) a northern zone where the lateral expansion is limited and combined with top-to-the-north extensional shearing along the Mont Pilat detachment zone and high-temperature wrenching. These asymmetric strain patterns relate to the expansion and deformation of granites emplaced below a detachment fault, during the uplift of a thickened area. Post-thickening combination of extensional and wrench tectonics is inferred.

Late glacial drainage systems along the northwestern margin of the Laurentide Ice Sheet

The evolution of drainage systems along the retreating northwestern Laurentide Ice Sheet was complex. The interaction of ice-margin configuration, topography and glacioisostasy resulted in a network of meltwater rivers that variably overflowed to the Arctic and Pacific Oceans and to the Gulf of Mexico. Glacial lakes also changed dramatically in size and location during the period of deglaciation. At the last (and all time) glacial maximum, the ice sheet extended into the eastern Cordillera, blocking northward and eastward drainage to the Arctic Ocean. Some meltwater and most non-glacial runoff were diverted through the mountains to the Yukon River basin, into Alaska and the Pacific Ocean. Retreat from the glacial maximum prior to 21 ka BP allowed proglacial drainage from the western margin of the ice sheet to flow into the Beaufort Sea/Arctic Ocean. Deglaciation was rapid after about 13 ka BP, with the present route of the lower Mackenzie River established between 13 and 11.5 ka BP. Continued ice retreat led to significant southward expansion of the Mackenzie/Beaufort drainage basin at about 11.5 ka BP through drainage capture of glacial Lake Peace, which previously had drained southeastward into the Missouri River and to the Gulf of Mexico. Very rapid ice retreat between 10.5 and 10 ka BP allowed glacial lake McConnell to expand down-slope in contact with the ice margin.Numerous glacial lakes occurred along the northwestern margin of the ice sheet during the maximum and retreat phases. These include ice-dammed glacial Lake Old Crow, which occupied unglaciated terrain of the northern Yukon, and glacial Lake Peace, which utilized a number of outlets as it migrated eastward with the ice front along the Peace Valley. The largest glacial lakes in the region were the result of glacioisostatic depression reversing the regional drainage. The Mackenzie Phase of glacial Lake McConnell was the second largest Pleistocene lake in North America (> 215,000 km2). Late glacial and post-glacial changes in drainage systems were largely in response to isostatic rebound.

Modelling the Dispersal of the First Americans through an Inhospitable Ice-free Corridor.

An ice-free corridor is believed to have existed during the late Pleistocene, but it is suspected that ecological conditions may have been severe. Hence, it is controversial whether the route could have been used by the first Americans in their southward expansion from Beringia to the interior of North America. Two demographic models, both assuming negative population growth in the corridor, are examined to evaluate the possibility of a successful crossing. First, a deterministic reaction-diffusion model shows that the condition permitting traversal could have been met, provided the diffusion coefficient (one-half the variance of random migratory activity) was not too large. Based on the mitochondrial DNA sequence divergence data of Vigilant et al. (1989), I obtain an estimate of the diffusion coefficient applicable to prehistoric hunter-gatherers, which is smaller than available estimates for recent humans. Second, the average waiting time between two successful crossings is derived from a probabilistic branching chain model with migration. Although there is much uncertainty regarding the appropriate values of the parameters, the average waiting time appears to be too long. Taken together, the theoretical analyses of this paper suggest that the ice-free corridor probably could not have served as the principal dispersal route.

A Numerical Study of Mesoscale Eddy Development over the Santa Barbara Channel

The development of the “midchannel eddy” over the Santa Barbara Channel represents a mesoscale response of the large-scale airflow to the combination of the diurnal heating cycle over land surfaces, the curvature of the coastline, and the orientation of major ridges with respect to the coastline. In this paper we analyze and discuss the results of a numerical simulation of mesoscale airflow over the Santa Barbara Channel and adjacent land areas on 23–24 September 1985, with emphasis upon nocturnal mesoscale eddy development. Simulated winds are compared with SCCCAMP 1985 wind observations. Both simulation and observations indicate inception of a midchannel eddy in the vicinity of Santa Barbara during the late evening of 23 September, followed by westward and southward expansion of the eddy. Our analyses indicate that simulated midchannel eddy development is associated with the following sequence of events: 1) offshore-directed flow develops over coastal ridges in the early evening, associated with inertial rotation of the sea breeze; 2) a “warm pocket” appears south of the coastal ridge near Santa Barbara resulting in a hydrostatic pressure minimum at low levels; 3) easterly flow develops near the coast as an ageostrophic response to the pressure minimum, while westerly flow components are maintained over the southern part of the channel; and 4) the resulting eddy elongates as the easterly flow advects the warm pocket westward along the coast.

Modelling the differential impact of 1984 and 1950 sea‐surface temperatures on sahel rainfall

AbstractExperiments with the GISS general circulation model are analysed to evaluate the differential impact of the contrastingly different 1984 and 1950 sea‐surface temperature (SST) patterns on simulated precipitation over sub‐Saharan Africa. Simulations yielded significantly lower August rainfall with 1984 SST as compared with 1950 SST. Differences in the moisture convergence into the Sahel responsible for the different resultant precipitation conditions are related to different evolutions of key circulation features. These are, in turn, consistent with some 1984 vs. 1950 SST differences in the Atlantic Ocean. In the model scenario, anomalously warm surface waters in July 1984 deepened the near‐equatorial trough over the coastal waters adjacent to north‐west Africa, promoting a circulation that eventually inhibited moisture advection from the Gulf of Guinea to the Sahel. This atmospheric evolution included a southward expansion of the West African Mid‐tropospheric jet, which has been observed to occur during dry summers. The study suggests that this structure is a symptom of drought rather than a cause.

Large-Scale Atmospheric Circulation Features of Warm and Cold Episodes in the Tropical Pacific

Ship observations of sea surface temperature (SST), sea level pressure and surface wind, and satellite measurements of outgoing longwave radiation (OLR) (an indicator of deep tropical convection) are used to describe the large-scale atmospheric circulation over the tropical Pacific during composite warm and cold episodes. Results are based on linear regression analysis between the circulation parameters and an index of SST in the tropical Pacific during the period 1946–85 (1974–89 for OLR). Warm episodes along the Peru coast (i.e., El Niño events) and basin-wide warmings associated with the Southern Oscillation are examined separately. Charts of the total as well as anomalous fields of SST, sea level pressure, surface wind and OLR for both warm and cold episodes are presented. SST and surface wind anomalies associated with warm episodes are consistent with the results of Rasmusson and Carpenter (1982). El Niño events are characterized by strong positive SST anomalies along the coasts of Ecuador and Peru and along the equator eastward of 130°W, and by an equatorward expansion and intensification of the Inter Tropical Convergence Zone (ITCZ) over the eastern Pacific. Basin-wide warm episodes exhibit positive SST anomalies along the equator eastward of 170°E, a southward expansion and intensification of the ITCZ, and an eastward shift and strengthening of the Indonesian convective zone. The movements of the precipitation zones are in good agreement with anomalous large scale surface wind convergence, Meridional wind anomalies dominate the anomalous surface convergence throughout the tropical Pacific. Surface winds are consistent with the sea level pressure distribution, with down-gradient flow near the equator, and with Ekman balance in the subtropics. A center of below normal sea level pressure over the equatorial eastern Pacific, distinct from the negative pressure anomalies over the subtropical southeast Pacific, is observed during basin-wide warm episodes. This equatorial feature is highly correlated with local SST and appears to be a boundary layer phenomenon. There is a net increase in deep convection over the tropical Pacific during warm episodes. Enhanced convection in the ITCZ during warm years is not accompanied by a net increase in surface wind convergence. A comparison between precipitation and surface wind convergence suggests that moisture convergence extends through a deeper layer in the equatorial western Pacific than in the ITCZ over the eastern Pacific. The contrasting distributions of surface relative humidity, total cloudiness and air-sea temperature difference over the eastern tropical Pacific during basin-wide warm and cold episodes are described in the context of boundary layer processes.

THE ZHUANG MINORITY IN THE MING ERA

AbstractIt has long been known that the southward expansion of the Chinese people which ultimately formed today's southern China was both a political and cultural process.’ While this southward movement may, in Confucian terms, have contributed to the “civilization” of the region's inhabitants, it also came at their expense as they ultimately were deprived of their autonomy. The most numerous of the southern peoples are known in China as the Zhuang and in Vietnam as the Nung. An important point in their history came in the Ming era (1368–1644), when “ethnic” or Han Chinese first attempted to fully incorporate the Zhuang into the imperial administrative system, in place of an earlier and looser recognition of Zhuang local autonomy by the Chinese government. This process was political in the sense that its purpose was to substitute a new and Chinese-ordered political hierarchy for that of the Zhuang. It was cultural in that the new order conflicted with important elements in Zhuang culture. The Zhuang resis...

Large‐ and small‐scale dynamics of the polar cusp

Photometric observations from two stations on Svalbard, Norway, have been used to map the location and dynamics of polar cusp auroras. Cases showing the behavior of cusp auroras and the local magnetic field related to changes in the interplanetary magnetic field (IMF) and irregularities in the solar wind plasma are presented. Dynamical phenomena with different time scales are studied. Southward and northward expansions of the midday sector of the auroral oval are discussed in relation to southward and northward turnings of the magnetosheath magnetic field and geomagnetic substorm activity. Examples showing no direct relationship to substorm activity are presented. Intensifications and rapid motions of discrete auroral structures in the cusp region are shown to be associated with local Pi‐type magnetic pulsations, each event lasting a few minutes. These small‐scale dynamical phenomena are discussed in relation to the concept of impulsive penetration of plasma irregularities across the dayside magnetopause, from the magnetosheath to the polar cusp region of the magnetosphere.

Paleoclimatic evidence for Cenozoic migration of Alaskan terranes

Chronostratigraphic and paleoclimatic comparisons of microfossils from deep‐sea cores, from samples of an exploratory drill hole, and from dredged rock of the Gulf of Alaska with coeval microfossil assemblages on the North American continent provide constraints on the northward migration of the Yakutat block, the Prince William terrane and the Pacific plate during Tertiary time. The comparative paleolatitudes of microfauna and flora provide three main constraints. (1) The Prince William terrane was in its present position with respect to North America (at high latitudes, 50° ± 5°N) by middle Eocene time (40–42 Ma), consistent with models derived from paleomagnetic data. (2) The adjacent Yakutat block was 30° ± 5° south of its present position in early Eocene (50 Ma), 20° ± 5° south in middle Eocene (40–44 Ma), and 15° ± 5° south in late Eocene time (37–40 Ma), thus requiring a northward motion of about 30° since 50 Ma. Moreover, the Yakutat block was at least 10° south of the Prince William terrane during Eocene time. These data are consistent with migration of the Yakutat block with the Pacific and Kula plates for at least the last 50 Ma. (3) site 192 on the Pacific plate was at about 15° ± 5°N latitude in the late Cretaceous (68 Ma), at 30° ± 5°N in early Eocene (50 Ma), at 40° ± 5°N in middle Eocene (40–44 Ma), at 45° ± 5°N in late Eocene (37–40 Ma), and north of 50° ± 5°N in latest Eocene to early Oligocene time (34–37 Ma). These paleolatitudes, based on planktonic foraminiferal assemblages, indicate northward drift consistent with the North America‐Pacific plate reconstructions from about 68 Ma to 40 Ma (Engebretson, 1982). However, from Cretaceous to early Eocené time, faunal data indicate significantly lower latitudinal positions, and from Oligocwne to early Miocene time, significantly higher latitudinal positions. These discrepancies can be explained by the northward expansion of tropical faunas during the globally warm early Tertiary and southward expansion of cold subarctic faunas as a result of global cooling during Oligocene time.

Spatial development of X-ray emission during the impulsive phase of a solar flare

The flare of 11 November, 1980, 17∶25 UT occurred in a magnetically complex region. It was preceded by some ten minutes by a gradual flare originating over the magnetic inversion line, close to a small sunspot. This seems to have triggered the main flare (at 70 000 km distance) which originated between a large sunspot and the inversion line. The main flare started at 17∶23∶20 UT with a slight enhancement of hard X-rays (E > 30 keV) accompanied by the formation of a dark loop between two Hα bright ribbons. In 3–8 keV X-rays a southward expansion started at the same time, with ν ∼- 500 km s −1. At the same time a surge-like expansion started. It was observable slightly later in Hα, with southward velocities of ≳ 200 km s−1. The dark Hα loop dissolved at ∼ 17∶24 UT at which time several impulsive phenomena started such as a complex of hard X-ray bursts localized in a small area. At the end of the impulsive phase at 17∶25∶40 UT, a coronal explosion occurred directed southward with an initial expansion velocity of ∼ 1800 km s−1, decreasing in 40 s to ∼500 km s−1.

Egypt and the enlargement of the EEC: Impact on the agricultural sector

This article examines the impact of the second enlargement of the EEC on the agricultural sector of Egypt. The authors consider the impacts on Egypt's agricultural trade and, through the use of a linear programming model, the long term impacts of EEC enlargement. The authors conlude that, in short run, the southward expansion of the EEC will impose only a limited additional burden on the Egyptian economy. But, in the long run the burden placed on Egypt by increased protectionism in the expanded EEC could be much more severe.

Distribution of quartz in late Quaternary Atlantic sediments in relation to climate

The distribution of quartz in the surface sediments of the Atlantic Ocean reflects derivation from continents by means of rivers, wind, ice, and coastal erosion. Enrichment of quartz thus supplied has occurred in some deep basins of especially the southern high latitudes from winnowing of finegrained clays by bottom currents. Although similar modes of quartz transport may have operated both during the Holocene and the last glacial maximum (18,000 yr B.P.), significant differences in the intensity of transport and in the locii of deposition, which are attributable to climatic variations during these times, exist in some areas of the Atlantic. In Holocene sediments of the eastern equatorial Atlantic, a band of high percent quartz exists directly off the present Saharan Desert and Sahel region and reflects the trade-wind transport of dusts from these arid and semiarid regions. During the last glacial maximum (18,000 yr B.P.), this high quartz band expanded southward by about 8° of latitude. This expansion was caused not only by the southward expansion of aridity and desert dunes but also by the southward migration of the northerly belt of trade winds during the last glaciation. Relatively high abundances and accumulation rates of quartz during the last glaciation suggest higher intensities of trade winds during that time compared to the Holocene. In the North Atlantic, the abundances of quartz in Holocene sediments are high adjacent to Greenland-Iceland and in the areas off Newfoundland-Labrador, and gradually decrease toward the central areas. The polar front and limit of sea-ice melting are at present confined to the northern part of the North Atlantic. The ice-rafting of quartz grains is, therefore, effective in the areas adjacent to Greenland and to some extent off Labrador causing high abundances in these areas. In contrast to this, during the last glaciation, the quartz abundances and accumulation rates are high in the central areas of North Atlantic around 45°N and decrease toward Greenland-Newfoundland. The migration of the polar front to as far south as 45°N and the consequent southward migration of sea-ice melting and ice-rafting during the last glaciation apparently caused this change in distribution. In addition to ice-rafting at present, wave or current reworking of relict glacial-marine detritus may have caused the high abundance of quartz in the surface sediments off Newfoundland-Labrador. In 18,000 yr B.P. sediments of the Norwegian Sea, the area of high percent quartz (>10%) is more extensive than that in Holocene sediments. This reflects the greater influence of ice-rafting or glacier activity in the sediment dispersal in the Norwegian Sea during the last glacial times.

Ecological experiments with Sargassum muticum

In spite of the controversy surrounding the accidental introduction of the Japanese seaweed Sargassutn muticum (Yendo) Fensholt onto two continents, the startling south-ward expansion of its range on the Pacific coast of North America (Norton, 1977 a), and the failure of an eradication campaign on the south coast of England, surprisingly little is known about the ecology of this species. Work has recently begun in both southern California and Britain (Nicholson et al. 1977; Lewey & Farnham, 1977). Unfortunately the ecological studies in Britain have been hampered by the conflicting aims of trying to study the plant and at the same time trying to eradicate it.