Unification of the Australian cratons before the formation of Nuna

2020 ◽  
Author(s):  
Uwe Kirscher ◽  
Ross Mitchell ◽  
Yebo Liu ◽  
Adam Nordsvan ◽  
Grant Cox ◽  
...  
Keyword(s):  
Building Blocks ◽  
Plate Motion ◽  
Central Pacific ◽  
Polar Wander ◽  
Central Pacific Ocean ◽  
The North ◽  
Rock Formations ◽  
Pine Creek ◽  
The Individual ◽  
Related Characteristic

<p>The paleogeography and chronology of the Paleoproterozoic supercontinent Nuna are highly debated. To further test the paleogeography of Australian cratons in the leadup to Nuna formation, we present new paleomagnetic results from two Paleoproterozoic rock formations in North Australia. First, we obtained paleomagnetic directions from the 1825±4 Ma, bimodal Plum Tree Creek Volcanics sequence located within the Pine Creek Inlier of the North Australian Craton. Second, we studied the 1855±2 Ma layered mafic-ultramafic ‘Toby’ intrusion from the Kimberley Craton (KC). Samples from both study areas reveal high quality, stable, magnetite related characteristic remanent magnetization directions. Combining within-site clustered mean directions, we obtained two paleopoles, which plot proximal to each other in the present day central Pacific Ocean, off the east coast of Australia. These results agree with previous interpretation that the Kimberly Craton was amalgamated with the rest of the North Australian Craton (NAC) prior to ca. 1.85 Ga. Comparing these new results with slightly younger poles from the NAC and slightly older, rotated poles form the West Australian Craton (WAC) reveal a high degree of clustering suggesting very minimal absolute plate motion between ca. 1.9-1.85 and 1.6 Ga before the final amalgamation of Nuna. All available paleomagnetic poles agree with an assembly, or close juxtaposition, of the two major Australian cratons (NAC and WAC) before 1.8 Ga. Furthermore, the individual virtual geomagnetic poles from the potentially slow cooled Toby intrusion show a non-fisherian distribution along a great circle. This spread might be related to previously interpreted major true polar wander events based on Laurentian data, which would be global if such an interpretation is correct. The assembly of proto-Australia prior to ca. 1.85 Ga roughly 250 to 300 Myr before the final stage of supercontinent Nuna’s amalgamation ca. 1.6 Ga suggests that assembling of major building blocks, such as Australia and Laurentia for the supercontinent Nuna and Gondwana for the supercontinent Pangea, is an important step in the formation of supercontinents.</p>

scholarly journals Temporal Variability of Dissolved Organic Radiocarbon in the Deep North Pacific Ocean

Radiocarbon ◽  
2018 ◽  
Vol 60 (4) ◽  
pp. 1115-1123 ◽  
Author(s):  
Ellen R M Druffel ◽  
Sheila Griffin ◽  
Ning Wang ◽  
Brett D Walker
Keyword(s):  
Pacific Ocean ◽  
Temporal Variability ◽  
North Pacific Ocean ◽  
Spatial Inhomogeneity ◽  
Central Pacific ◽  
North Central ◽  
Central Pacific Ocean ◽  
The Past ◽  
The North ◽  
C Value

ABSTRACTWe report marine dissolved organic carbon (DOC) ∆14C from seawater collected from the North central Pacific Ocean (NCP) in 2015. These measurements show DOC ∆14C values averaged –235±5‰ (n=3) in the mixed layer (24–81 m) and –544±5‰ (n=5) in the deep water (1500–5139 m). A comparison of these data with two previously published DOC ∆14C profiles from the NCP in 1985 and 1987 reveals that deep DOC ∆14C values have decreased. We discuss several possible mechanisms that could cause such a shift in DOC ∆14C values, including spatial inhomogeneity and temporal variability due to changes in the dissolution and ∆14C value of surface derived particles in the deep sea. We find that forthcoming profiles of DOC ∆14C results from the NCP will determine the primary mechanisms controlling deep DOC ∆14C distributions, and changes over the past three decades.

scholarly journals Rapid emplacement of massive Duluth Complex intrusions within the North American Midcontinent Rift

Geology ◽  
2020 ◽  
Author(s):  
Nicholas L. Swanson-Hysell ◽  
Steven A. Hoaglund ◽  
James L. Crowley ◽  
Mark D. Schmitz ◽  
Yiming Zhang ◽  
...  
Keyword(s):  
Plate Motion ◽  
Magmatic Activity ◽  
Midcontinent Rift ◽  
Polar Wander ◽  
Large Igneous Provinces ◽  
Duluth Complex ◽  
The North ◽  
Apparent Polar Wander Path ◽  
Igneous Provinces ◽  
Lithospheric Extension

The Duluth Complex (Minnesota, USA) is one of the largest mafic intrusive complexes on Earth. It was emplaced as the Midcontinent Rift developed in Laurentia’s interior during an interval of magmatism and extension from ca. 1109 to 1084 Ma. This duration of magmatic activity is more protracted than is typical for large igneous provinces interpreted to have formed from decompression melting of upwelling mantle plumes. While the overall duration was protracted, there were intervals of more voluminous magmatism. New 206Pb/238U zircon dates for the anorthositic and layered series of the Duluth Complex constrain these units to have been emplaced ca. 1096 Ma in <1 m.y. (duration of 500 ± 260 k.y.). Comparison of paleomagnetic data from these units with Laurentia’s apparent polar wander path supports this interpretation. This rapid emplacement bears similarities to the geologically short duration of well-dated large igneous provinces. These data support hypotheses that call upon the co-location of lithospheric extension and anomalously hot upwelling mantle. This rapid magmatic pulse occurred >10 m.y. after initial magmatism following >20° of latitudinal plate motion. A likely scenario is one in which upwelling mantle encountered the base of Laurentian lithosphere and flowed via “upside-down drainage” to locally thinned lithosphere of the Midcontinent Rift.

scholarly journals Revisiting the trend in the occurrences of the warm Arctic-cold Eurasian continent temperature pattern

2020 ◽  
Author(s):  
Lejiang Yu ◽  
Shiyuan Zhong ◽  
Cuijuan Sui ◽  
Bo Sun
Keyword(s):  
Surface Temperature ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Temperature Pattern ◽  
Self Organizing Map ◽  
Central Pacific ◽  
Central Pacific Ocean ◽  
The North ◽  
Eurasian Continent ◽  
Increasing Trend

Abstract. The recent increasing trend of warm Arctic, cold continents has attracted much attention, but it remains debatable as to what forces are behind this phenomenon. Here, we revisited surface-temperature variability over the Arctic and Eurasian continent by applying the Self-Organizing-Map (SOM) technique to gridded daily surface temperature data. Nearly 40 % of the surface temperature trends are explained by the nine SOM patterns that depict the switch to the current warm Arctic-cold Eurasia pattern at the beginning of this century from the reversed pattern that dominated the 1980s and the 90s. Further, no cause-effect relationship is found between the Arctic sea-ice loss and the cold spells in high-mid latitude Eurasian continent suggested by earlier studies. Instead, the increasing trend in warm Arctic-cold Eurasia pattern appears to be related to the anomalous atmospheric circulations associated with two Rossby wavetrains triggered by rising sea surface temperature (SST) over the central North Pacific and the North Atlantic Oceans. On interdecadal timescale, the recent increase in the occurrences of the warm Arctic-cold Eurasia pattern is a fragment of the interdecadal variability of SST over the Atlantic Ocean as represented by the Atlantic Multidecadal Oscillations (AMO), and over the central Pacific Ocean.

scholarly journals First record of Spotted Knifejaw, Oplegnathus punctatus (Temminck & Schlegel, 1844) (Oplegnathidae) in the southern South China Sea

Check List ◽  
2021 ◽  
Vol 17 (4) ◽  
pp. 1195-1198
Author(s):  
Yusri Yusuf ◽  
Ying Giat Seah ◽  
Md Repin Izarenah ◽  
Jen Nie Lee
Keyword(s):  
South China Sea ◽  
South China ◽  
First Record ◽  
Southern South China Sea ◽  
Central Pacific ◽  
China Sea ◽  
Central Pacific Ocean ◽  
The North ◽  
Southward Extension ◽  
First Time

Oplegnathus punctatus (Temminck & Schlegel, 1844) is reported for the first time in the southern South China Sea, off Pulau Tenggol, Malaysia. This species is native to the north-western and central Pacific Ocean and mainly occurs in subtropical and warm temperate waters. This record is a significant southward extension of its range and also represents the first documentation of the family Oplegnathidae in Malaysia. 

scholarly journals Intermediate water flows in the South West Pacific from OUTPACE and THOT Argo floats

2018 ◽  
Author(s):  
Simon Barbot ◽  
Anne Petrenko ◽  
Christophe Maes
Keyword(s):  
Velocity Shear ◽  
Cyclonic Eddy ◽  
Intermediate Water ◽  
Central Pacific ◽  
Argo Floats ◽  
Central Pacific Ocean ◽  
Mesoscale Dynamics ◽  
Zonal Jets ◽  
The North ◽  
Deep Waters

Abstract. Thanks to the autonomous Argo floats of the OUTPACE cruise and of the THOT project, some features of intermediate flow dynamics, around 1000 m depth, within the Southwest and Central Pacific Ocean (156° E–150° W, around 19° S) are described. In the Coral sea, we highlight minima in dissolved oxygen of 140 μmol kg−1 that are associated with the signature of a southward transport of waters between two zonal jets: from the North Vanuatu Jet to the North Caledonia Jet. This transport takes place in the core of a cyclonic eddy or via the path between a cyclonic eddy and an anticyclonic one, highlighting the importance of mesoscale dynamics in upper thermocline and surface layers. Further east, we observe a strong meridional velocity shear with long-term float trajectories going either eastward or westward in the lower thermocline. More interestingly, these trajectories also exhibit some oscillatory features. Those trajectories can be explained by a single Rossby wave of 160 days period and 855 km wavelength. Considering the thermohaline context, we confirm the meridional shear of zonal velocity and highlight a permanent density front that corresponds to the interface between Antarctic Intermediate Waters and North Pacific Deep Waters. Hence both circulation and thermohaline contexts are highly favorable to instabilities and wave propagation.

scholarly journals Iron Profile of Octopus Hubbsorum (Cephalopoda: Octopodidae) for Enrichment of the Mexican Diet

2018 ◽  
Author(s):  
Juliano Palacios-Abrantes ◽  
Virginia melo Ruiz ◽  
Rafael Diaz-Garcia ◽  
Cesar Gazga-Urioste ◽  
Brian Urbano
Keyword(s):  
Main Role ◽  
Central Pacific ◽  
Human Welfare ◽  
Mexican Pacific ◽  
Central Pacific Ocean ◽  
The North ◽  
Food And Agriculture ◽  
Food And Agriculture Organization ◽  
Central Nervous Systems ◽  
Iron Profile

FAO (Food and Agriculture Organization of the United Nations) declared that 12% of the world’s population is undernourished while in Mexico the number is around 5%. Minerals are essential for the daily diet; iron (Fe) is an important mineral on human welfare because it has a main role on the function of the immune and central nervous systems, among others. Most Mexicans fulfill their iron requirements from vegetables, which are poorly absorbed; nevertheless, in coastal populations, where seafood-rich in iron- is available, it is not consumed on a regular diet. The aim of this work was to analyze minerals, focusing on the iron content of Octopus hubbsorum B (Cephalopoda: Octopodidae), an animal of the Mexican Pacific coast. Three specimens were analyzed, two from the north and one from central Pacific Ocean. Data obtained for the central Pacific Octopus was 0.008% and data for the North Pacific were 0.008% and 0.011%, repectively. In conclusion, the supply of iron for the Mexican diet provided by Octopus hubbsorum B is significant, therefore is recommended to consume more of this resource, to diminish iron deficiency, a world-wide problem, and to improve human health

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