Geophysical Studies of North African Cenozoic Volcanic Areas I: Haruj Assuad, Libya

1974 ◽  
Vol 11 (7) ◽  
pp. 998-1006 ◽  
Author(s):  
J. M. Ade-Hall ◽  
P. H. Reynolds ◽  
P. Dagley ◽  
A. E. Mussett ◽  
T. P. Hubbard ◽  
...  
Keyword(s):  
Geomagnetic Field ◽  
Age Dating ◽  
Main Concern ◽  
Volcanic Area ◽  
North African ◽  
Weighted Mean ◽  
African Plate ◽  
North Central ◽  
The North ◽  
The Difference

This study is the first of a series in which a main concern will be to establish the Neogene absolute motion of the African Plate. A combined palaeomagnetic and K–Ar whole rock age dating study has been made of the Haruj Assuad basaltic volcanic area of central Libya. Seventy volcanic units, largely pahoehoe basaltic flows, were sampled in the north-central Haruj Assuad in an area centred on 27°45′ N, 017°30′E. Precisely defined paleomagnetic directions were obtained for 68 of the volcanic units and a weighted mean pole at 83°N, 171°E (δp = 5°, δm = 9°) obtained. This pole is just significantly different at the 95% level from the geographic pole. The difference between the paleomagnetic and geographic poles is thought to be largely the result of a degree of nonrepresentative sampling of the geomagnetic field. K–Ar radiometric age data indicate that volcanic activity in the Haruj Assuad area continued at least over the interval 6.0 to 0.4 my. The polarities of dated units are in agreement with the predictions of the time polarity scale. The ages of dated flows indicate that most of the flows presently exposed are younger than 2.2 my (i.e.) Upper Pliocene and younger. A scheme for assigning relative ages to groups of flows by degree of surface weathering is now calibrated in part with absolute ages.

Geophysical Studies of North African Cenozoic Volcanic Areas: II. Jebel Soda, Libya

1975 ◽  
Vol 12 (8) ◽  
pp. 1257-1263 ◽  
Author(s):  
J. M. Ade-Hall ◽  
P. H. Reynolds ◽  
P. Dagley ◽  
A. E. Mussett ◽  
T. P. Hubbard
Keyword(s):  
Volcanic Activity ◽  
Dipole Field ◽  
Age Dating ◽  
Data Selection ◽  
Main Concern ◽  
Data Sets ◽  
Volcanic Area ◽  
North African ◽  
African Plate ◽  
Combined Data

This study is the second of a series in which a main concern will be to try to establish the Neogene absolute motion of the African Plate. A combined paleomagnetic and K–Ar whole rock age dating study has been made of the Jebel Soda basaltic volcanic area of central Libya. Sixty basaltic flows were sampled in an area centered on 28°45′N, 15°30′E. Precisely defined paleomagnetic directions were obtained for 57 of the flows. Considerable attention has been given to the problem of data selection to obtain a best measure of the pole representing the dipole field during the period of volcanic activity. The equatorial nature of the directions, with equivalent poles extending continuously to 30°N latitude, provide a problem in data selection. Similar characteristics are apparent in the results of Schult and Soffel (1973) for the same area. A provisional average pole for the combined data sets, located at 73°N, 195°E(K: 26, A95: 5.6°) is significantly different from the geographic pole. Reasons for the 17 °divergence of paleomagnetic and geographic poles are discussed briefly.

Policing Colonial Migrants

2019 ◽  
Vol 42 (4) ◽  
pp. 655-680 ◽  
Author(s):  
Danielle Beaujon
Keyword(s):  
Intimate Relationships ◽  
Personal Knowledge ◽  
Coercive Power ◽  
North African ◽  
Municipal Council ◽  
The North ◽  
African Community ◽  
The Difference ◽  
Insight Into

Abstract In 1923 the Parisian Municipal Council created a special police unit to control North Africans in Paris, known as the Brigade Nord-Africaine (BNA). During its twenty-year tenure, the BNA controlled the North Africans they policed through intimation and violence, but also through personal knowledge of the community. The BNA's harsh tactics had to be balanced by its officers' admitted reliance on North Africans for information. This article explores both the uniquely discriminatory and colonial nature of the BNA and the nuanced, intimate relationships that developed between the officers and the North African community. A repatriation of colonial control, the BNA reified the difference of those it policed, uniquely targeting North Africans but also offering a space of possible agency for them in interwar Paris. The BNA gives us insight into policing in the 1930s, demonstrating the acceptability of targeted policing but also showing the limits of coercive power. En 1923, le Conseil municipal de Paris créa une brigade destinée à contrôler les Nord-Africains domiciliés à Paris : la Brigade nord-africaine (BNA). Pendant ses vingt années d'existence, la BNA employa non seulement l'intimidation et la violence, mais aussi des tactiques reposant sur une connaissance intime de la communauté, pour contrôler celle-ci. Le travail de la BNA exigeait un équilibre entre la répression et une entente avec la communauté nord-africaine qui fournissait des renseignements essentiels aux officiers. Cet article examine d'une part la nature discriminatoire et coloniale de la BNA et d'autre part, les rapports intimes et nuancés qui se tissèrent entre la brigade et les Nord-Africains. Rapatriant à Paris des formes de contrôle coloniales, la BNA contribua à réifier la différence des Nord-Africains qu'elle surveillait tout en leur offrant une certaine capacité d'action limitée. Etudier la BNA permet d'élucider les préjugés des policiers de l'époque, tout comme les limites de leur pouvoir coercitif.

Comparative Precambrian geochronology of the North American, European, and Siberian Shields

1969 ◽  
Vol 6 (3) ◽  
pp. 357-365 ◽  
Author(s):  
R. A. Burwash
Keyword(s):  
Statistical Treatment ◽  
Geologic History ◽  
Northern Asia ◽  
North Central ◽  
Mean Values ◽  
The North ◽  
Central United States ◽  
History Of ◽  
The Difference ◽  
The Baltic

A comparison of average values of U–Pb, Rb–Sr, and K–Ar isotopic dates from Precambrian shields in North America, Europe, and northern Asia suggests three major orogenies common to all areas. U–Pb and Rb–Sr age determinations, qualified by the more numerous K–Ar data, suggest mean values of 2600 ± 100 m.y., 1800 ± 100 m.y. and 1000 ± 100 m.y. An earlier event at 3300 to 3500 m.y. is locally recognizable in the Baltic Shield, the Ukrainian Shield, and the north-central United States. Anorogenic igneous events intermediate between the major orogenies are indicated in the Canadian, Ukrainian, and Aldan Shields, but these are as yet unmatched outside their own restricted settings.Isotopic dates are divided into two categores: anorogenic and orogenic. Within a specified orogeny, dates are further divided into precrystalline, syncrystalline, and postcrystalline. Regional correlations ideally should be based only on syncrystalline dates, recording times of final crystallization, unmodified by subsequent processes except initial cooling. Depth of crystallization and rate of uplift determine the difference between true and apparent time of crystallization. Precrystalline dates (survival values) and postcrystalline (rejuvenated or overprinted) dates should be excluded from the designated span of major orogenies.Rigorous statistical treatment of isotopic dates seems unwarranted on the basis of uncertainties in the geologic history of most rock bodies. Histograms may aid in the identification of anorogenic and precrystalline dates.

U–Pb zircon age dating of a rapakivi granite batholith in Rangnim massif, North Korea

2007 ◽  
Vol 144 (3) ◽  
pp. 547-552 ◽  
Author(s):  
MINGGUO ZHAI ◽  
JINGHUI GUO ◽  
PENG PENG ◽  
BO HU
Keyword(s):  
North China Craton ◽  
North Korea ◽  
North China ◽  
Granulite Facies ◽  
Age Dating ◽  
Weighted Mean ◽  
Zircon Age ◽  
Metasedimentary Rocks ◽  
The North ◽  
Granite Batholith

Rapakivi granites and several small leucogabbroic and gabbroic bodies are located in the Rangnim Massif, North Korea. The largest batholith in the Myohyang Mountains covers an area of 300 km2 and was intruded into Precambrian metamorphosed rocks. It has a SHRIMP U–Pb zircon weighted mean 207Pb/206Pb age of 1861 ± 7 Ma. The country rocks of rapakivi granites are Neoarchaean orthogneisses and Palaeo-Mesoproterozoic graphite-bearing metasedimentary rocks of granulite facies, and they are similar to those of the rapakivi granites and anorthosites exposed in South Korea and in the North China Craton. We conclude that the three massifs in the Korean Peninsula commonly record an identical Palaeo-Mesoproterozoic anorogenic magmatic event, indicating that they have a common Precambrian basement with the North China Craton.

Engelmann × Sitka spruce hybrids in central British Columbia

1989 ◽  
Vol 19 (9) ◽  
pp. 1190-1193 ◽  
Author(s):  
G. K. Kiss
Keyword(s):  
British Columbia ◽  
Sitka Spruce ◽  
North Central ◽  
The North ◽  
Plantation Age ◽  
The Difference ◽  
Total Tree ◽  
Hybrid Spruce

Several crosses of Engelmann × Engelmann and Engelmann × Sitka spruce (one parent) were studied. Average crossability of the latter was 24.5%. Average heights of the pure Engelmann and the hybrid spruce were 361.6 and 183.6 cm, respectively, at plantation age 13 (16 years from seed). The difference in height appeared to be the result of repeated winter kill of large proportions of the previous summer's growth. Age to age correlations for total tree heights at 3–7 and 7–13 years old were highly significant. Based on these results, Engelmann × Sitka spruce hybrids are not recommended for reforestation purposes in the north-central interior of British Columbia. However, there are indications that preselecting better genotypes may improve the performance of the resulting hybrids; thus, further research in this direction is warranted.

New contribution to the survey of the theory of the acrotony on the branch of one year grapevine: I - Investigation in the Tunisian vineyard

OENO One ◽  
2000 ◽  
Vol 34 (3) ◽  
pp. 121
Author(s):  
Béchir Ezzili ◽  
M. Bejaoui
Keyword(s):  
Apical Part ◽  
The Other ◽  
North African ◽  
The North ◽  
Result Show ◽  
The Difference ◽  
One Year ◽  
The One ◽  
New Hypothesis ◽  
Test Result

<p style="text-align: justify;">Research in the conduct mode of grapevines other than the north African goblet incited us to make an investigation on the no bursting on table vine canes and to study if the vestigial dormancy is equivalent to acrotony phenomenon. Results of this survey clearly show that this phenomenon varies from one year to the other and that there is a negative interrelationship between the percentage of buds no bursted and the diameter of the basis of the cane on the one hand and of the top on the other hand. The difference in diameters of the basis and apical part is weakly correlated with the percentage of buds no bursted. As a result we concluded that at the level of the cane, the percentage of buds no bursted doesn't only depend on the diameter of the cane but also on the fixing of this one on the carrier axis. The bibliographic survey puts in exergue the low temperature role. We tried to dissociate the acrotony phenomenon and the vestigial dormancy. Test result show that the long cane fixing at the temperature of 4°C during 10 days removes partially or completely the vestigial dormancy but the phenomenon of the acrotony persists. We examined the qualitative answers of the investigation. In Tunisia, on long canes of Muscatel of Italy, a certain percentage of one year old presents both the acrotony (80 p. cent) and the basitony phenomena (8 p. cent) in 1995. The discussion of results of the investigation allowed us to give out a new hypothesis of work concerning the phenomenon which we will to verify.</p>

scholarly journals Paläoklimatologische Eindrücke aus Neuseeland

1965 ◽  
Vol 16 (1) ◽  
pp. 226-238
Author(s):  
Martin Schwarzbach
Keyword(s):  
New Zealand ◽  
Windward Side ◽  
Western Coast ◽  
Volcanic Area ◽  
The North ◽  
Long Time ◽  
Glacier Ice ◽  
Climatic History ◽  
The Difference ◽  
Wet Climate

Abstract. Some observations and remarks about the climate and paleoclimate of New Zealand, founded on journeys and the work of New Zealandic geologists. Some peculiarities of the climate (fig. 1). New Zealand has a relatively cool and wet climate (similar to Tasmania at the present). There is a very conspicious difference between the very humid windward side and the arid lee-side of the Southern Alps (also in the vegetation, fig. 2). „Edaphically caused deserts" begin to develop in the volcanic area of the North Island (fig. 3). The glaciers on the western coast of New Zealand (fig. 4), especially Franz Josef and Fox Glaciers, are impressive examples for the coexistence of lush, nearly subtropical rainforests (with tree-ferns) with glacier ice (figs. 6, 8). Therefore they are especially important for paleoclimatologists and for the interpretation of climatic indicators. Both glaciers have their tongues near the sea, nearly 2000 mts. below snow-line. Their recession (fig. 7) was 1200 and 1800 m respectively in 21 years. The cause for the low position of the tongues is to bee seen in high precipitation in connexion with the altitude and steepness of the mountains. Climatic history of New Zealand. The Quaternary is not treated; it only is referred to the influence of recent tectonic movements on the terraces. — The climate of the Tertiary was temperate to subtropical and humid. Maximal temperatures did not occur (as in Europe and North America) in the older, but (as in Australia) in the middle Tertiary (fig. 9). The author tries to explain this difference by the combination of 2 curves (fig. 10): one is the curve of changing latitude, caused by drift, the other is the general trend of the decline of temperature in Tertiary time. Because Australia obviously moved towards the equator, but Europe (if at all) towards the pole, the resulting curve is different in both continents. — Also the Mesozoic climate was neither tropical nor arid. Perhaps the Permian was a little warmer than in Australia. Compared with Australia, the climatic history is distinctly different. Australia changed from a polar climate to a subtropical and tropical one since the Carboniferous-Permian period, but New Zealand seems to have remained more or less in the same climatic zone during this long time. We don't yet know whether the difference between New Zealand and Australia is only apparent (caused by gaps in our knowledge), or is caused by an independent northward drift of both regions (Australia quickly, New Zealand more slowly).

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