An Upper Ediacaran Glacial Period in Cadomia: the Granville tillite (Armorican Massif) – sedimentology, geochronology and provenance

Abstract In the Cadomian orogenic belt a package of glacigenic sedimentary deposits have been recently described in the Armorican Massif (Normandy, France). The Granville Tillite Member, the middle part of the upper Granville Formation, is late Ediacaran in age. Maximum depositional ages of the pre- and syn-glacial sedimentary deposits obtained by LA-ICP-MS U–Pb detrital zircon dating indicate a maximum age of 561 ± 3 Ma. Combined with geochronological data on the previously described glacial deposits in Cadomia, West Africa, Arabia and Iran, the Granville Tillite Member appears to represent an Upper Ediacaran Glacial Period in northern peri-Gondwana, clearly younger than the c. 580 Ma old Gaskiers glaciation. Detailed mapping and analysis of the depositional regime of two sections near the city of Granville are indicative of two independent glaciomarine lower and upper tillite deposits separated by a distinct conglomeratic marker horizon, evidently a massive gravel beach horizon deposited during an interglacial stage. Age spectra of detrital zircon U–Pb ages constrain the palaeogeographical position of the upper Granville Formation to the periphery of the West African Craton. Post-Gaskiers aged glaciations in Cadomia and in West Africa should be grouped into an Upper Ediacaran Glacial Period dated at c. 565 Ma. This glacial period seems not to be related to the negative δ13C Shuram–Wonoka anomaly. Sedimentary deposits formed during the Upper Ediacaran Glacial Period show a scattered distribution along the marginal orogens of the Gondwana supercontinent independent of palaeolatitude and are coupled most likely to contemporaneous orogenic processes and uplift.

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Preliminary detrital zircon U-Pb Geochronology of the Wasatch Formation, Powder River Basin, Wyoming

The Mountain Geologist ◽

10.31582/rmag.mg.56.3.247 ◽

2019 ◽

Vol 56 (3) ◽

pp. 247-266

Author(s):

Ian Anderson ◽

David H. Malone ◽

John Craddock

Keyword(s):

River Basin ◽

Detrital Zircon ◽

Middle Part ◽

Detrital Zircons ◽

Powder River Basin ◽

Zircon Age ◽

Lower Eocene ◽

The North ◽

Mountain Front ◽

Fluvial Sandstone

The lower Eocene Wasatch Formation is more than 1500 m thick in the Powder River Basin of Wyoming. The Wasatch is a Laramide synorgenic deposit that consists of paludal and lacustrine mudstone, fluvial sandstone, and coal. U-Pb geochronologic data on detrital zircons were gathered for a sandstone unit in the middle part of the succession. The Wasatch was collected along Interstate 90 just west of the Powder River, which is about 50 km east of the Bighorn Mountain front. The sandstone is lenticular in geometry and consists of arkosic arenite and wacke. The detrital zircon age spectrum ranged (n=99) from 1433-2957 Ma in age, and consisted of more than 95% Archean age grains, with an age peak of about 2900 Ma. Three populations of Archean ages are evident: 2886.6±10 Ma (24%), 2906.6±8.4 Ma (56%) and 2934.1±6.6 Ma (20%; all results 2 sigma). These ages are consistent with the age of Archean rocks exposed in the northern part of the range. The sparse Proterozoic grains were likely derived from the recycling of Cambrian and Carboniferous strata. These sands were transported to the Powder River Basin through the alluvial fans adjacent to the Piney Creek thrust. Drainage continued to the north through the basin and eventually into the Ancestral Missouri River and Gulf of Mexico. The provenance of the Wasatch is distinct from coeval Tatman and Willwood strata in the Bighorn and Absaroka basins, which were derived from distal source (>500 km) areas in the Sevier Highlands of Idaho and the Laramide Beartooth and Tobacco Root uplifts. Why the Bighorn Mountains shed abundant Eocene strata only to the east and not to the west remains enigmatic, and merits further study.

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THE PROVENANCE OF GLACIAL TILL DEPOSITED IN ONG VALLEY, CENTRAL TRANSANTARCTIC MOUNTAINS DETERMINED BY LA-ICP-MS OF DETRITAL ZIRCON

10.1130/abs/2016am-285013 ◽

2016 ◽

Author(s):

Evan J. Miranda ◽

◽

Daniel Morgan ◽

Jaakko Putkonen ◽

Greg Balco ◽

...

Keyword(s):

Detrital Zircon ◽

Glacial Till ◽

Icp Ms ◽

Transantarctic Mountains

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Genomic investigation of a dengue virus outbreak in Thiès, Senegal, in 2018

Scientific Reports ◽

10.1038/s41598-021-89070-1 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Amy Gaye ◽

Tolla Ndiaye ◽

Mouhamad Sy ◽

Awa B. Deme ◽

Alphonse B. Thiaw ◽

...

Keyword(s):

West Africa ◽

Dengue Virus ◽

Clinical Signs ◽

Health Concern ◽

Public Health Concern ◽

Local Circulation ◽

Viral Genomes ◽

Genomic Characterization ◽

The City

AbstractDengue virus is a major and rapidly growing public health concern in tropic and subtropic regions across the globe. In late 2018, Senegal experienced its largest dengue virus outbreak to date, covering several regions. However, little is known about the genetic diversity of dengue virus (DENV) in Senegal. Here we report complete viral genomes from 17 previously undetected DENV cases from the city of Thiès. In total we identified 19 cases of DENV in a cohort of 198 individuals with fever collected in October and November 2018. We detected 3 co-circulating serotypes; DENV 3 was the most frequent accounting for 11/17 sequences (65%), 4 (23%) were DENV2 and 2 (12%) were DENV1. Sequences were most similar to recent sequences from West Africa, suggesting ongoing local circulation of viral populations; however, detailed inference is limited by the scarcity of available genomic data. We did not find clear associations with reported clinical signs or symptoms, highlighting the importance of testing for diagnosing febrile diseases. Overall, these findings expand the known range of DENV in Senegal, and underscore the need for better genomic characterization of DENV in West Africa.

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Paleomagnetism of the ~860 Ma Manso dyke swarm, West Africa: implications for the assembly of Rodinia

10.5194/egusphere-egu21-13336 ◽

2021 ◽

Author(s):

Paul Yves Jean Antonio ◽

Lenka Baratoux ◽

Ricardo Ivan Ferreira Trindade ◽

Sonia Rousse ◽

Anani Ayite ◽

...

Keyword(s):

West Africa ◽

West African ◽

Dyke Swarm ◽

Jigsaw Puzzle ◽

The West ◽

West African Craton ◽

Contact Test ◽

Fine Grained ◽

Paleomagnetic Pole ◽

Coarse To Fine

The West African Craton (WAC) is one of the major cratons in the Rodinia jigsaw puzzle (~1000&#8211;750 Ma). In the Rodinian models, the position of West Africa is mainly constrained by the assumption that it had been a partner of Amazonia since the Paleoproterozoic. Unfortunately, no paleomagnetic data are available for these cratons when the Rodina supercontinent is considered tectonically stable (~1000-750 Ma). Thus, every new reliable paleomagnetic pole for the West African Craton during the Neoproterozoic times is of paramount importance to constrain its position and testing the Rodinia models. In this study we present a combined paleomagnetic and geochronological investigation for the Manso dyke swarm in the Leo-Man Shield, southern West Africa (Ghana). The ~860 Ma emplacement age for the NNW-trending Manso dykes is thus well-constrained by two new U-Pb apatite ages of 857.2 &#177; 8.5 Ma and 855 &#177; 16 Ma, in agreement with baddeleyite data. Remanence of these coarse-to-fine grained dolerite dykes is carried by stable single to pseudo-single domain (SD-PSD) magnetite. A positive baked-contact test, associated to a positive reversal test (Class-C), support the primary remanence obtained for these dykes (13 sites). Moreover, our new paleomagnetic dataset satisfy all the seven R-criteria (R=7). The ~860 Ma Manso pole can thus be considered as the first key Tonian paleomagnetic pole for West Africa. We propose that the West Africa-Baltica-Amazonia-Congo-S&#227;o Francisco were associated in a long-lived WABAMGO juxtaposition (~1100&#8211;800 Ma).Keywords: West Africa, Neoproterozoic, Tonian, Rodinia, paleomagnetism.&#160;

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U–Pb age and Lu–Hf signatures of detrital zircon from Palaeozoic sandstones in the Oslo Rift, Norway

Geological Magazine ◽

10.1017/s0016756813000885 ◽

2013 ◽

Vol 151 (5) ◽

pp. 816-829 ◽

Cited By ~ 21

Author(s):

MAGNUS KRISTOFFERSEN ◽

TOM ANDERSEN ◽

ARILD ANDRESEN

Keyword(s):

Detrital Zircon ◽

Inductively Coupled Plasma ◽

Late Carboniferous ◽

Isotopic Signatures ◽

Inductively Coupled ◽

Source To Sink ◽

Icp Ms ◽

Plasma Mass Spectrometry ◽

Isotope Analyses ◽

Multiple Episodes

AbstractU–Pb and Lu–Hf isotope analyses of detrital zircon from the latest Ordovician (Hirnantian) Langøyene Formation, the Late Silurian Ringerike Group and the Late Carboniferous Asker Group in the Oslo Rift were obtained by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Overall the U–Pb dating yielded ages within the range 2861–313 Ma. The U–Pb age and Lu–Hf isotopic signatures correspond to virtually all known events of crustal evolution in Fennoscandia, as well as synorogenic intrusions from the Norwegian Caledonides. Such temporally and geographically diverse source areas likely reflect multiple episodes of sediment recycling in Fennoscandia, and highlights the intrinsic problem of using zircon as a tracer-mineral in ‘source to sink’ sedimentary provenance studies. In addition to its mostly Fennoscandia-derived detritus, the Asker Group also have zircon grains of Late Devonian – Late Carboniferous age. Since no rocks of these ages are known in Fennoscandia, these zircons are inferred to be derived from the Variscan Orogen of central Europe.

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Pemodelan Prediksi Banjir Kota Medan Dengan Menggunakan Sistem Informasi Geografis

Tunas Geografi ◽

10.24114/tgeo.v8i1.13480 ◽

2019 ◽

Vol 8 (1) ◽

pp. 19

Author(s):

M S Roganda

Keyword(s):

Rainfall Intensity ◽

Flood Hazard ◽

Middle Part ◽

Flood Inundation ◽

Flood Modeling ◽

Analysis Technique ◽

Study Techniques ◽

The Impact ◽

The City

This study aims to (1) Determine the results of inundation in Medan based on the scenario of rainfall intensity <60 mm / day and> 60 mm / day. (2) Determine the level of flood hazard based on flood inundation scenarios of rainfall intensity <60 mm / day and> 60 mm / day conducted in Medan City. (3) Determine the impact caused by the flooding based on interpretation techniques from the results of flood modeling conducted in Medan City. Data collection techniques used in this study are documentary study techniques. The data analysis technique was carried out with three stages, including (1) Determining the overflow results. (2) Determine the classification of flood hazard levels. (3) Identifying areas that affect flood hazard areas per district. The results in this study are (1) based on the scenario of rainfall intensity <60 mm / day, there is no inundation flooding, whereas based on the scenario of rainfall intensity> 60 mm / day shows several points of flood inundation especially in the northern part of Medan City. (2) flood hazard based on flood inundation scenario results in rainfall intensity <60 mm / day does not pose any danger at all whereas flood hazard based on flood inundation results rainfall intensity scenario> 60 mm / day shows that in the northern part there are two dominant classes namely class high and low, in the middle part of the city the dominant class terrain is medium and in the southern part of Medan City the dominance by medium and low classes. (3) Based on interpretation techniques carried out on the Flood Impact Map Based on Districts in Medan, it can be seen that several districts in Medan have several flood hazard classes such as low, medium, and high.Keywords: Medan City, Rain, Flood Modeling AbstrakPenelitian ini bertujuan untuk (1) Mengetahui hasil banjir genangan di Kota Medan berdasarkan skenario intensitas curah hujan < 60 mm/hari dan > 60 mm/hari. (2) Mengetahui tingkat bahaya banjir berdasarkan hasil banjir genangan skenario intensitas curah hujan < 60 mm/hari dan > 60 mm/hari yang dilakukan di Kota Medan. (3) Mengetahui dampak yang disebabkan banjir berdasarkan teknik interpretasi dari hasil pemodelan banjir yang dilakukan di Kota Medan. Teknik pengumpulan data yang digunakan dalam penelitian ini adalah teknik studi dokumenter. Teknik analisis data dilakukan dengan tiga tahapan diantaranya (1) Menentukan hasil luapan. (2) Menentukan klasifikasi tingkat bahaya banjir. (3) Mengidentifikasi wilayah-wilayah yang berdampak ke daerah bahaya banjir per kecamatan. Hasil dalam penelitian ini adalah (1) berdasarkan skenario intensitas curah hujan < 60 mm/hari tidak terjadi banjir genangan sedangkan berdasarkan skenario intensitas curah hujan > 60 mm/hari menunjukkan beberapa titik terjadi genangan banjir terutama di bagian utara Kota Medan. (2) bahaya banjir berdasarkan hasil banjir genangan skenario intensitas curah hujan < 60 mm/hari tidak menimbulkan bahaya sama sekali sedangkan bahaya banjir berdasarkan hasil banjir genangan skenario intensitas curah hujan > 60 mm/hari memperlihatkan pada bagian utara ada dua kelas yang dominan yaitu kelas tinggi dan rendah, pada bagian tengah kota medan kelas yang dominan adalah sedang dan di bagian selatan Kota Medan dominasi oleh kelas sedang dan rendah. (3) Berdasarkan teknik interpretasi yang dilakukan pada Peta Dampak Banjir Berdasarkan Kecamatan Di Kota Medan terlihat bahwa beberapa kecamatan di Kota Medan memiliki beberapa kelas bahaya banjir seperti rendah, sedang dan tinggi.Kata Kunci : Kota Medan, Hujan, Pemodelan Banjir

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Caledonian terrane amalgamation of Svalbard: detrital zircon provenance of Mesoproterozoic to Carboniferous strata from Oscar II Land, western Spitsbergen

Geological Magazine ◽

10.1017/s0016756813000174 ◽

2013 ◽

Vol 150 (6) ◽

pp. 1103-1126 ◽

Cited By ~ 33

Author(s):

DETA GASSER ◽

ARILD ANDRESEN

Keyword(s):

Detrital Zircon ◽

Large Scale ◽

Strike Slip ◽

Western Coast ◽

Zircon Age ◽

The North ◽

Tectonic History ◽

Icp Ms ◽

Depositional Age ◽

Sveconorwegian Orogen

AbstractThe tectonic origin of pre-Devonian rocks of Svalbard has long been a matter of debate. In particular, the origin and assemblage of pre-Devonian rocks of western Spitsbergen, including a blueschist-eclogite complex in Oscar II Land, are enigmatic. We present detrital zircon U–Pb LA-ICP-MS data from six Mesoproterozoic to Carboniferous samples and one U–Pb TIMS zircon age from an orthogneiss from Oscar II Land in order to discuss tectonic models for this region. Variable proportions of Palaeo- to Neoproterozoic detritus dominate the metasedimentary samples. The orthogneiss has an intrusion age of 927 ± 3 Ma. Comparison with detrital zircon age spectra from other units of similar depositional age within the North Atlantic region indicates that Oscar II Land experienced the following tectonic history: (1) the latest Mesoproterozoic sequence was part of a successor basin which originated close to the Grenvillian–Sveconorwegian orogen, and which was intruded byc. 980–920 Ma plutons; (2) the Neoproterozoic sediments were deposited in a large-scale basin which stretched along the Baltoscandian margin; (3) the eclogite-blueschist complex and the overlying Ordovician–Silurian sediments probably formed to the north of the Grampian/Taconian arc; (4) strike-slip movements assembled the western coast of Spitsbergen outside of, and prior to, the main Scandian collision; and (5) the remaining parts of Svalbard were assembled by strike-slip movements during the Devonian. Our study confirms previous models of complex Caledonian terrane amalgamation with contrasting tectonic histories for the different pre-Devonian terranes of Svalbard and particularly highlights the non-Laurentian origin of Oscar II Land.

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Prologue

African Dominion ◽

10.23943/princeton/9780691196824.003.0001 ◽

2019 ◽

pp. 1-8

Author(s):

Michael A. Gomez

Keyword(s):

West Africa ◽

Political Power ◽

The State ◽

The Third ◽

History Of ◽

City State ◽

Relationship Of ◽

The Relationship ◽

The City

This prologue provides an overview of the history of early and medieval West Africa. During this period, the rise of Islam, the relationship of women to political power, the growth and influence of the domestically enslaved, and the invention and evolution of empire were all unfolding. In contrast to notions of an early Africa timeless and unchanging in its social and cultural categories and conventions, here was a western Savannah and Sahel that from the third/ninth through the tenth/sixteenth centuries witnessed political innovation as well as the evolution of such mutually constitutive categories as race, slavery, ethnicity, caste, and gendered notions of power. By the period's end, these categories assume significations not unlike their more contemporary connotations. All of these transformations were engaged with the apparatus of the state and its progression from the city-state to the empire. The transition consistently featured minimalist notions of governance replicated by successive dynasties, providing a continuity of structure as a mechanism of legitimization. Replication had its limits, however, and would ultimately prove inadequate in addressing unforeseen challenges.

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