Upper Triassic to Lower Cretaceous continental and coastal saline lake evaporites inthe Atacama region of northern Chile

1987 ◽  
Vol 124 (5) ◽  
pp. 467-475 ◽  
Author(s):  
M. Suarez ◽  
C. M. Bell
Keyword(s):  
Lower Cretaceous ◽  
Lower Jurassic ◽  
Upper Triassic ◽  
Northern Chile ◽  
Subtropical Zone ◽  
Playa Lake ◽  
Latitudinal Position ◽  
River Deposits ◽  
Geographical Position ◽  
Lake Deposits

AbstractEvaporites within Upper Triassic to Lower Cretaceous sequences in the Atacama region of northern Chile are interpreted as the deposits of continental and coastal saline lakes. Halite casts and finely laminated calcareous evaporites, intercalated with alluvial and fluvial sediments, are probably playa lake deposits. These continental evaporites have been recognized in Upper Triassic alluvial sediments (Cifuncho Formation), in Upper Triassic–Lower Jurassic braided river deposits (basal unit of the Pan de Azúcar Formation), and within a sequence of Lower Cretaceous aeolian, alluvial and playa lake mudflat sediments (Quebrada Monardes Formation). Lower Cretaceous evaporites between marine limestones (Lautaro Formation) and continental redbeds (Quebrada Monardes Formation) were probably deposited in coastal saline lagoons, produced during a regionally extensive marine regression.These sequences, and other similar successions in northern Chile, provide a record of almost continuous evaporite deposition, and hence of arid to semi-arid conditions, since Upper Triassic times. These conditions were primarily the result of a constant latitudinal position within the subtropical zone. A contributary factor was the geographical position of the area, initially on the west coast of Gondwanaland and subsequently on the coast of South America, with cold, northward-flowing ocean currents and offshore winds.

Transition from a passive to active continental margin setting for the NE Asian continental margin during the Mesozoic: Insights from the sedimentary formations and paleogeography of the eastern Jiamusi Massif, NE China

2021 ◽  
Author(s):  
Yini Wang ◽  
Wenliang Xu ◽  
Feng Wang
Keyword(s):  
Continental Margin ◽  
Lower Cretaceous ◽  
Active Continental Margin ◽  
Volcanic Rocks ◽  
Lower Jurassic ◽  
Pacific Plate ◽  
Upper Triassic ◽  
Passive Continental Margin ◽  
Ne China ◽  
Margin Setting

The Mesozoic tectonic evolution of the NE Asian continental margin has received much attention in recent years. However, previous studies focused mainly on the petrogenesis of igneous rocks and their relationship with Mesozoic tectonics, and there have been few studies of the Mesozoic sedimentary formations of the NE Asian continental margin. We combined zircon U-Pb ages with Hf isotopic and biostratigraphic data to reconstruct the Mesozoic paleogeography of the NE Asian continental margin. The results indicate that Mesozoic strata of the eastern Jiamusi Massif, NE China, include the Upper Triassic Nanshuangyashan Formation (Norian), Lower Jurassic volcanic rocks, and Lower Cretaceous Longzhaogou Group. The Upper Triassic Nanshuangyashan Formation consists of a suite of alternating marine and terrestrial sedimentary rocks with abundant fossils that formed in a passive continental margin setting. The Lower Jurassic strata comprise a suite of calc-alkaline volcanic rocks that include basaltic andesites, andesites, and rhyolites that formed in an active continental margin setting related to initial subduction of the Paleo-Pacific Plate beneath Eurasia. The Lower Cretaceous Longzhaogou Group belong to alternating marine and terrestrial sedimentary formations that formed in an active continental margin setting related to subduction of the Paleo-Pacific Plate. Here, we integrate these data to reconstruct the Mesozoic tectonic history of the NE Asian continental margin, which comprises a Late Triassic passive continental margin, the initiation of subduction of the Paleo-Pacific Plate in the Early Jurassic, and westward subduction and rollback of the Paleo-Pacific Plate in the Early Cretaceous.

A new species of Crenoptychoptera Kalugina, 1985 (Diptera: Ptychopteridae) from the Middle–Late Jurassic of Jiyuan Basin, China

2021 ◽  
Vol 4 (1) ◽  
pp. 027-029
Author(s):  
YU-MING LIU ◽  
DI-YING HUANG
Keyword(s):  
New Species ◽  
Lower Cretaceous ◽  
Type Species ◽  
Late Jurassic ◽  
Upper Jurassic ◽  
Lower Jurassic ◽  
Upper Triassic ◽  
The Family ◽  
Extinct Genus ◽  
A New Species

Ptychopteridae is an ancient and rather diverse nematoceran family with three extant and 12 fossil genera subdivided into 80 extinct species belonging to five subfamilies (Eskov & Lukashevich, 2015; Lukashevich, 2019, 2020; Liu & Huang, 2020). Several undescribed ptychopterid larvae from the Upper Triassic of Germany represent the oldest record of the family (Barth et al., 2011). Crenoptychoptera Kalugina, 1985, an extinct genus belonging to the subfamily Eoptychopterinae Handlirsch, 1906, includes seven described species. All these species were recorded from the Lower Jurassic to the Lower Cretaceous of Eurasia: C. dobbertinensis Ansorge, 1998 from the Lower Jurassic of the Former Clay in Germany (Lukashevich et al., 1998), C. conspecta Lukashevich, 1995 from the Lower Jurassic of Ust-Baley in Russia (Lukashevich, 1995), the type species C. antica Kalugina, 1985 and C. defossa Kalugina, 1985 from the Middle Jurassic of the Kubekovo in Russia (Kalugina & Kovalev, 1985), C. bavarica Krzemiński & Ansorge, 1995 from the Upper Jurassic of Wegscheid in Germany (Krzemiński & Ansorge, 1995), C. liturata Lukashevich, 2011 from Upper Jurassic of Shar Teg in Mongolia, and C. gronskayae Kalugina, 1989 from the Upper Jurassic to Lower Cretaceous of Kempendyay in Russia (Kalugina, 1989; Lukashevich, 2011). Three species discovered from the Daohugou beds of China have been assigned to Crenoptychoptera (Hao et al., 2009), but a following study suggested that they should be placed in Axymyiidae (Zhang, 2010).

scholarly journals Mesozoic micropalaeontology of exploration well Elf 55/30–1 from the Fasnet Basin, offshore southwest Ireland

1986 ◽  
Vol 5 (1) ◽  
pp. 19-29 ◽  
Author(s):  
Nigel R. Ainsworth ◽  
Nicola F. Horton
Keyword(s):  
Lower Cretaceous ◽  
Lower Jurassic ◽  
Late Triassic ◽  
Ecological Distribution ◽  
Exploration Well

Abstract. The geology, biostratigraphy and palaeoecology of exploration well Elf 55/30–1 in the Fastnet Basin are summarised. The biostratigraphical and ecological distribution of the foraminifera and Ostracoda from the late Triassic, the Lower Jurassic and the Lower Cretaceous are reviewed with reference to microfaunas elsewhere in Europe. Selected microfossil taxa are illustrated.

The Lower Cretaceous Way Group of northern Chile: An alluvial fan-fan delta complex

1986 ◽  
Vol 46 (1-2) ◽  
pp. 1-22 ◽  
Author(s):  
S. Flint ◽  
H. Clemmey ◽  
P. Turner
Keyword(s):  
Lower Cretaceous ◽  
Alluvial Fan ◽  
Northern Chile ◽  
Fan Delta

scholarly journals MESOZOIC RADIOLARIANS FROM RHYTHMICALLY LAYERED SEDIMENTS OF THE RIMSKY-KORSAKOV ISLANDS (PETER THE GREAT BAY, JAPAN SEA) AND THEIR SIGNIFICANCE FOR DETERMINING THE TRIASSIC-JURASSIC BOUNDARY

2021 ◽  
pp. 39-54
Author(s):  
O.L. Smirnova ◽  
◽  
E.A. Bessonova ◽  
T.A. Emelyanova ◽  
◽  
...  
Keyword(s):  
Peter The Great Bay ◽  
Japan Sea ◽  
Research Area ◽  
Lower Jurassic ◽  
Upper Triassic ◽  
Peter The Great ◽  
Great Bay ◽  
The Pacific ◽  
Stratigraphic Division ◽  
First Time

The results of the biostratigraphic study based on the radiolarian analysis of the rhythmically layered terrigenous deposits from the Islands of the Rimsky-Korsakov Archipelago (Peter the Great Bay, Japan Sea) have been presented. These deposits are most similar to the medium-grained turbidites. For the first time the distribution and stratigraphic division of the boundary sediments of the upper Triassic and lower Jurassic separated by a marking layer were substantiated in the research area. On the basis of comparisons with isochronous zonal units of the Pacific and Tethyan areas in the upper Triassic sediments of the studied sections, layers with Globolaxtorum tozeri (upper Rhaetian) were established, and in the lower Jurassic zone Pantanellium tanuense Zone (Hettangian) was traced and layers with Parahsuum simplum (Sinemurian – Pliensbachian) were established.

An ichthyosaur forefin from the Triassic of British Columbia exemplifying Jurassic features

1991 ◽  
Vol 28 (10) ◽  
pp. 1553-1560 ◽  
Author(s):  
C. McGowan
Keyword(s):  
British Columbia ◽  
North America ◽  
Lower Jurassic ◽  
Upper Triassic ◽  
New Material ◽  
Important Site

New ichthyosaur material is reported from an Upper Triassic locality on Williston Lake, northeastern British Columbia. The paucity of ichthyosaurs from the Triassic of North America make this a potentially important site. An isolated forefin is described, which is unlike that of any Triassic species from North America but which compares closely with certain Lower Jurassic species from England and Germany. The new material suggests that the transition in the ichthyosaurian fauna at the close of the Triassic may have been less abrupt than was previously supposed.

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