Detrital zircons and the interpretation of palaeogeography, with the Variscan Orogeny as an example

AbstractAnalysis of the distribution of detrital zircon grains is one of the few parameters by which Precambrian palaeogeography may be interpreted. However, the break-up of Pangea and the subsequent dispersal of some of its fragments around the Indian Ocean demonstrate that zircon analysis alone may be misleading, since zircons indicate their original derivation and not their subsequent plate-tectonic pathways. Based on analysis of Precambrian–Ordovician zircon distributions, the presence of microcontinents and separating oceans in the north Gondwanan realm has been rejected in favour of an undivided pre-Variscan continental northwards extension of Africa to include Iberia, Armorica and neighbouring southern European terranes, based on analysis of Precambrian–Ordovician zircon distribution. However, contrasting views, indicating the presence of three peri-Gondwanan oceans with complete Wilson cycles, are reinforced here by a critical reappraisal of the significance of that Variscan area detrital zircon record together with a comparison of the evolution of the present-day Indian Ocean, indicating that Iberia, Armorica and other terranes were each separate from the main Gondwanan craton during the early Palaeozoic Era.

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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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Research Gap Analysis of Remote Sensing Application in Fisheries: Prospects for Achieving the Sustainable Development Goals

Remote Sensing ◽

10.3390/rs13051013 ◽

2021 ◽

Vol 13 (5) ◽

pp. 1013

Author(s):

Kuo-Wei Yen ◽

Chia-Hsiang Chen

Keyword(s):

Sustainable Development ◽

Indian Ocean ◽

Atlantic Ocean ◽

The Sustainable Development ◽

The North ◽

The Pacific ◽

Development Goals ◽

The Indian Ocean ◽

The Pacific Ocean ◽

Research Hotspots

Remote sensing (RS) technology, which can facilitate the sustainable management and development of fisheries, is easily accessible and exhibits high performance. It only requires the collection of sufficient information, establishment of databases and input of human and capital resources for analysis. However, many countries are unable to effectively ensure the sustainable development of marine fisheries due to technological limitations. The main challenge is the gap in the conditions for sustainable development between developed and developing countries. Therefore, this study applied the Web of Science database and geographic information systems to analyze the gaps in fisheries science in various countries over the past 10 years. Most studies have been conducted in the offshore marine areas of the northeastern United States of America. In addition, all research hotspots were located in the Northern Hemisphere, indicating a lack of relevant studies from the Southern Hemisphere. This study also found that research hotspots of satellite RS applications in fisheries were mainly conducted in (1) the northeastern sea area in the United States, (2) the high seas area of the North Atlantic Ocean, (3) the surrounding sea areas of France, Spain and Portugal, (4) the surrounding areas of the Indian Ocean and (5) the East China Sea, Yellow Sea and Bohai Bay sea areas to the north of Taiwan. A comparison of publications examining the three major oceans indicated that the Atlantic Ocean was the most extensively studied in terms of RS applications in fisheries, followed by the Indian Ocean, while the Pacific Ocean was less studied than the aforementioned two regions. In addition, all research hotspots were located in the Northern Hemisphere, indicating a lack of relevant studies from the Southern Hemisphere. The Atlantic Ocean and the Indian Ocean have been the subjects of many local in-depth studies; in the Pacific Ocean, the coastal areas have been abundantly investigated, while offshore local areas have only been sporadically addressed. Collaboration and partnership constitute an efficient approach for transferring skills and technology across countries. For the achievement of the sustainable development goals (SDGs) by 2030, research networks can be expanded to mitigate the research gaps and improve the sustainability of marine fisheries resources.

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Carbon-14 in the Southern Indian Ocean

Radiocarbon ◽

10.1017/s0033822200010055 ◽

1980 ◽

Vol 22 (3) ◽

pp. 684-692 ◽

Cited By ~ 6

Author(s):

Georgette Delibrias

Keyword(s):

Surface Water ◽

Indian Ocean ◽

Water Samples ◽

Sea Water ◽

Time Lag ◽

Vertical Profiles ◽

Carbon 14 ◽

Middle Latitudes ◽

The North ◽

The Indian Ocean

14C measurements were carried out on sea water samples collected in 1973, in the Indian ocean. The results obtained for 9 vertical profiles between 27° S and 48°S are presented. In surface water, the bomb 14C content is maximum at middle latitudes. A time lag relative to the north hemisphere bomb 14C delivery is apparent. In the more southern latitudes, 14C content remains very low.

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The Geology of Portuguese Nyasaland

Geological Magazine ◽

10.1017/s0016756800109501 ◽

1922 ◽

Vol 59 (5) ◽

pp. 200-212

Author(s):

Robert R. Walls

Keyword(s):

Indian Ocean ◽

East Africa ◽

The South ◽

The North ◽

Dark Continent ◽

The Indian Ocean

Portuguese Nyasaland is the name given to the most northern part of Portuguese East Africa, lying between Lake Nyasa and the Indian Ocean. It is separated from the Tanganyika territory in the north by the River Rovuma and from the Portuguese province of Mozambique in the south by the River Lurio. The territory measures about 400 miles from east to west and 200 miles from north to south and has an area of nearly 90,000 square miles. This territory is now perhaps the least known part of the once Dark Continent, but while the writer was actually engaged in the exploration of this country in 1920–1, the Naval Intelligence Division of the British Admiralty published two handbooks, the Manual of Portuguese East Africa and the Handbook of Portuguese Nyasaland, which with their extensive bibliographies contained practically everything that was known of that country up to that date (1920). These handbooks make it unnecessary in this paper to give detailed accounts of the work of previous explorers.

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Art. VII.—Notes on Persian Belúchistán. From the Persian of Mirza Mehdy Khán. Published Teheran, July, 1875

Journal of the Royal Asiatic Society ◽

10.1017/s0035869x00016816 ◽

1876 ◽

Vol 9 (1) ◽

pp. 147-154

Author(s):

A. H. Schindler

Keyword(s):

Indian Ocean ◽

Temperate Climate ◽

The South ◽

The West ◽

The North ◽

The People ◽

The Indian Ocean ◽

The Hill ◽

Cool Climate

The part of Belúchistán now under Persian rule is bounded upon the north by Seistán, upon the east by Panjgúr and Kej, upon the south by the Indian Ocean, and upon the west by Núrámshír, Rúdbár, and the Báshákerd mountains.This country enjoys a variety of climates; almost unbearable heat exists on the Mekrán coast, we find a temperate climate on the hill slopes and on the slightly raised plains as at Duzek and Bampúr, and a cool climate in the mountainous districts Serhad and Bazmán. The heat at Jálq is said to be so intense in summer that the gazelles lie down exhausted in the plains, and let themselves be taken by the people without any trouble.

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U–Pb Dating and Hf Isotopes Analysis of Detrital Zircons of the Shanxi Formation in the Otuokeqi Area, Northwestern Ordos Basin

Geofluids ◽

10.1155/2021/6693005 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Jiaxuan Song ◽

Hujun Gong ◽

Jingli Yao ◽

Huitao Zhao ◽

Xiaohui Zhao ◽

...

Keyword(s):

Detrital Zircon ◽

North China ◽

Ordos Basin ◽

Detrital Zircons ◽

Oscillatory Zoning ◽

Edge Structure ◽

Material Recycling ◽

The North ◽

Upper Paleozoic ◽

The Ordos Basin

The Paleozoic strata are widely distributed in the northwest of the Ordos Basin, and the provenance attributes of the basin sediments during this period are still controversial. In this paper, the detrital zircon LA-MC-ICPMS U-Pb age test was conducted on the drilling core samples of the Shanxi Formation of the Upper Paleozoic in the Otuokeqi area of the Ordos Basin, and the provenance age and the characteristic of the Shanxi formation in the Otuokeqi area in the northwest were discussed. The cathodoluminescence image shows that the detrital zircon has a clear core-edge structure, and most of the cores have clear oscillatory zonings, which suggests that they are magmatic in origin. Zircons have no oscillatory zoning structure that shows the cause of metamorphism. The age of detrital zircon is dominated by Paleoproterozoic and can be divided into four groups, which are 2500~2300 Ma, 2100~1600 Ma, 470~400 Ma, and 360~260 Ma. The first two groups are the specific manifestations of the Precambrian Fuping Movement (2.5 billion years) and the Luliang Movement (1.8 billion years) of the North China Craton. The third and fourth groups of detrital zircons mainly come from Paleozoic magmatic rocks formed by the subduction and collision of the Siberian plate and the North China plate. The ε Hf t value of zircon ranges from -18.36 to 4.33, and the age of the second-order Hf model T DM 2 ranges from 2491 to 1175 Ma. The source rock reflecting the provenance of the sediments comes from the material recycling of the Paleoproterozoic and Mesoproterozoic in the crust, combined with the Meso-Neoproterozoic detrital zircons discovered this time, indicating that the provenance area has experienced Greenwellian orogeny.

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The Meridional Shift of the Midlatitude Westerlies over Arid Central Asia during the Past 21 000 Years Based on the TraCE-21ka Simulations

Journal of Climate ◽

10.1175/jcli-d-19-0798.1 ◽

2020 ◽

Vol 33 (17) ◽

pp. 7455-7478

Author(s):

Nanxuan Jiang ◽

Qing Yan ◽

Zhiqing Xu ◽

Jian Shi ◽

Ran Zhang

Keyword(s):

Indian Ocean ◽

North Atlantic ◽

North Atlantic Ocean ◽

Last Deglaciation ◽

The Past ◽

The North ◽

External Forcings ◽

The Indian Ocean ◽

The Last Deglaciation ◽

The North Atlantic

AbstractTo advance our knowledge of the response of midlatitude westerlies to various external forcings, we investigate the meridional shift of midlatitude westerlies over arid central Asia (ACA) during the past 21 000 years, which experienced more varied forcings than the present day based on a set of transient simulations. Our results suggest that the evolution of midlatitude westerlies over ACA and driving factors vary with time and across seasons. In spring, the location of midlatitude westerlies over ACA oscillates largely during the last deglaciation, driven by meltwater fluxes and continental ice sheets, and then shows a long-term equatorward shift during the Holocene controlled by orbital insolation. In summer, orbital insolation dominates the meridional shift of midlatitude westerlies, with poleward and equatorward migration during the last deglaciation and the Holocene, respectively. From a thermodynamic perspective, variations in zonal winds are linked with the meridional temperature gradient based on the thermal wind relationship. From a dynamic perspective, variations in midlatitude westerlies are mainly induced by anomalous sea surface temperatures over the Indian Ocean through the Matsuno–Gill response and over the North Atlantic Ocean by the propagation of Rossby waves, or both, but their relative importance varies across forcings. Additionally, the modeled meridional shift of midlatitude westerlies is broadly consistent with geological evidence, although model–data discrepancies still exist. Overall, our study provides a possible scenario for a meridional shift of midlatitude westerlies over ACA in response to various external forcings during the past 21 000 years and highlights important roles of both the Indian Ocean and the North Atlantic Ocean in regulating Asian westerlies, which may shed light on the behavior of westerlies in the future.

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Model system dynamics potential impact of disasters due to the re-period of the October 25th, 2010 earthquake in the Mentawai Islands

E3S Web of Conferences ◽

10.1051/e3sconf/202133107004 ◽

2021 ◽

Vol 331 ◽

pp. 07004

Author(s):

Aprilyanto ◽

I Dewa Ketut Kerta Widana ◽

Ady Subiyanto ◽

Hafizh Surya Islami

Keyword(s):

Indian Ocean ◽

System Dynamics ◽

Return Period ◽

Risk Mitigation ◽

Secondary Data ◽

Dynamics Modeling ◽

Mentawai Islands ◽

The North ◽

The Indian Ocean ◽

High Level

Geographically, the Mentawai Islands Regency has a territorial boundary with the sea. The north side is the Siberut Strait, the south side is bordered by the Indian Ocean, the east side is bordered by the Mentawai Strait, and the west side is bordered by the Indian Ocean. The Mentawai Islands Regency area has a high level of seismicity which makes it prone to earthquakes and tsunamis because it has an earthquake return period. Population and economic growth in the Mentawai Islands Regency continue to increase, resulting in a higher level of threat due to earthquakes and tsunamis to people and buildings. By using earthquake return period modeling based on secondary data and population and building growth modeling using system dynamics, Pentahelix can implement disaster risk mitigation in the Mentawai Islands Regency to reduce the risk of casualties and material losses. Based on the prediction that the Mentawai earthquake return period on October 25, 2010, will occur for 24 years to 57 years or around 2034 to 2067, and the results of system dynamics modeling with Powersim Studio 10 software, the number of vulnerable people affected is 24,764 people up to 42,944 people and potential losses. housing sector between 144.73 billion to 250.98 billion.

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Late Paleozoic tectonism of the Bogda region in Chinese North Tianshan: Insights from sedimentary provenance analysis

10.5194/egusphere-egu21-16422 ◽

2021 ◽

Author(s):

Qian Wang ◽

Guochun Zhao ◽

Yigui Han ◽

Jinlong Yao

Keyword(s):

Detrital Zircon ◽

Detrital Zircons ◽

Late Paleozoic ◽

Provenance Analysis ◽

The North ◽

Tectonic Transition ◽

Isotopic Analyses ◽

Zircon Morphology ◽

Detrital Zircon Ages ◽

T Values

The Chinese North Tianshan (CNTS) extends E-W along the southern part of the Central Asian Orogenic Belt and has undergone complicated accretion-collision processes in the Paleozoic. This study attempts to clarify the late Paleozoic tectonism in the region by investigating the provenance of the Late Paleozoic sedimentary successions from the Bogda Mountain in the eastern CNTS by U-Pb dating and Lu-Hf isotopic analyses of detrital zircons. Detrital zircon U-Pb ages (N=519) from seven samples range from 261 &#177; 4 Ma to 2827 &#177; 32 Ma, with the most prominent age peak at 313 Ma. There are Precambrian detrital zircon ages (~7%) ranged from 694 to 1024 Ma. The youngest age components in each sample yielded weighted mean ages ranging from 272 &#177; 9 Ma to 288 &#177; 5 Ma, representing the maximum depositional ages. These and literature data indicate that some previously-assumed &#8220;Carboniferous&#8221; strata in the Bogda area were deposited in the Early Permian, including the Qijiaojing, Julideneng, Shaleisaierke, Yangbulake, Shamaershayi, Liushugou, Qijiagou, and Aoertu formations. The low maturity of the sandstones, zircon morphology and provenance analyses indicate a proximal sedimentation probably sourced from the East &#173;Junggar Arc and the Harlik-Dananhu Arc in the CNTS. The minor Precambrian detrital zircons are interpreted as recycled materials from the older strata in the Harlik-Dananhu Arc. Zircon &#603;Hf(t) values have increased since ~408 Ma, probably reflecting a tectonic transition from regional compression to extension. This event might correspond to the opening of the Bogda intra-arc/back arc rift basin, possibly resulting from a slab rollback during the northward subduction of the North Tianshan Ocean. A decrease of zircon &#603;Hf(t) values at ~300 Ma was likely caused by the cessation of oceanic subduction and subsequent collision, which implies that the North Tianshan Ocean closed at the end of the Late Carboniferous. This research was financially supported by the Youth Program of Shaanxi Natural Science Foundation (2020JQ-589), the NSFC Projects (41730213, 42072264, 41902229, 41972237) and Hong Kong RGC GRF (17307918).

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The Linear Sensitivity of the North Atlantic Oscillation and Eddy-Driven Jet to SSTs

Journal of Climate ◽

10.1175/jcli-d-19-0038.1 ◽

2019 ◽

Vol 32 (19) ◽

pp. 6491-6511 ◽

Cited By ~ 5

Author(s):

Hugh S. Baker ◽

Tim Woollings ◽

Chris E. Forest ◽

Myles R. Allen

Keyword(s):

Indian Ocean ◽

North Atlantic Oscillation ◽

North Atlantic ◽

High Sensitivity ◽

Internal Variability ◽

The North ◽

The Indian Ocean ◽

The North Atlantic ◽

The North Atlantic Oscillation ◽

The Impact

Abstract The North Atlantic Oscillation (NAO) and eddy-driven jet contain a forced component arising from sea surface temperature (SST) variations. Due to large amounts of internal variability, it is not trivial to determine where and to what extent SSTs force the NAO and jet. A linear statistical–dynamic method is employed with a large climate ensemble to compute the sensitivities of the winter and summer NAO and jet speed and latitude to the SSTs. Key regions of sensitivity are identified in the Indian and Pacific basins, and the North Atlantic tripole. Using the sensitivity maps and a long observational SST dataset, skillful reconstructions of the NAO and jet time series are made. The ability to skillfully forecast both the winter and summer NAO using only SST anomalies is also demonstrated. The linear approach used here allows precise attribution of model forecast signals to SSTs in particular regions. Skill comes from the Atlantic and Pacific basins on short lead times, while the Indian Ocean SSTs may contribute to the longer-term NAO trend. However, despite the region of high sensitivity in the Indian Ocean, SSTs here do not provide significant skill on interannual time scales, which highlights the limitations of the imposed SST approach. Given the impact of the NAO and jet on Northern Hemisphere weather and climate, these results provide useful information that could be used for improved attribution and forecasting.

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