Fractionation and incipient self-granulitization during deep-crust emplacement of Lower Ordovician Valle Fértil batholith at the Gondwana active margin of South America

Jujuyaspis borealis is reported from earliest Ordovician (North American usage) limestones in central Texas and western Utah, the first time this species has been recognized in the United States. Jujuyaspis is a widespread olenid trilobite that occurs near the base of the Tremadoc Series in a variety of lithologies in North and South America, Europe, and Asia. When international agreement is reached on the exact horizon at or near the base of the Tremadoc Series that is to be used as the Cambrian–Ordovician boundary, Jujuyaspis will likely prove to be a very useful taxon for recognition of the boundary interval.

Download Full-text

Lower Ordovician graptolite biozonation and lithofacies of southern Bolivia: relevance for palaeogeographic interpretations

Geological Magazine ◽

10.1017/s0016756804009239 ◽

2004 ◽

Vol 141 (3) ◽

pp. 287-299 ◽

Cited By ~ 25

Author(s):

SVEN O. EGENHOFF ◽

JÖRG MALETZ ◽

BERND-DIETRICH ERDTMANN

Keyword(s):

South America ◽

Basin Evolution ◽

Early Ordovician ◽

The Pacific ◽

Lower Ordovician ◽

Lithostratigraphic Units ◽

Faunal Succession ◽

Argentine Precordillera

The interpretation of the lithofacies and basin evolution of the early Ordovician of southern Bolivia is based on a number of sections on an E–W transect. Lithostratigraphic units are extremely diachronous and only the available data on the graptolite biostratigraphy enabled an interpretation of the basin evolution. The newly proposed graptolite biozonation includes the biozones of Rhabdinopora flabelliformis, Adelograptus sp., Araneograptus murrayi, Hunnegraptus copiosus, Tetragraptus phyllograptoides, Expansograptus protobalticus, Expansograptus holmi, Baltograptus minutus, Azygograptus lapworthi and Isograptus victoriae. Isograptus victoriae is the first isograptid identified from Gondwanan South America. The early Ordovician succession of southern Bolivia is the most complete one documented from South America and can be used as a standard for this continent. The faunas are most easily correlated with the faunal succession of Scandinavia and without doubt belong to the Atlantic graptolite faunal province. They show distinct differences from coeval faunas of the Argentine Precordillera, referable to the Pacific faunal province.

Download Full-text

Jujuyaspis and associated trilobites from the Mungok Formation (Lower Ordovician), Yongwol, Korea

Journal of Paleontology ◽

10.1017/s0022336000017595 ◽

2000 ◽

Vol 74 (6) ◽

pp. 1031-1042 ◽

Cited By ~ 10

Author(s):

Dong Hee Kim ◽

Duck K. Choi

Keyword(s):

North America ◽

South America ◽

North China ◽

Lower Ordovician ◽

America South ◽

Mungok Formation ◽

First Time

The trilobite genus Jujuyaspis Kobayashi, 1936, an index fossil of earliest Ordovician age, is recorded from the Yosimuraspis Zone of the Mungok Formation (Lower Ordovician) for the first time in Korea. The Yosimuraspis Zone comprises Yosimuraspis vulgaris Kobayashi, 1960; Jujuyaspis sinensis Zhou in Chen et al., 1980; Elkanaspis jilinensis Qian in Chen et al 1985; and pilekid genus and species indeterminate. Closely comparable faunas to the Yosimuraspis Zone are well represented in North China. The occurrence of Jujuyaspis allows the correlation of the Yosimuraspis Zone with the earliest Ordovician faunas of North America, South America, and Scandinavia, and suggests that the Cambrian-Ordovician boundary in Korea be placed at the base of the Yosimuraspis Zone.

Download Full-text

The Geochemical and Isotopic Record of Wilson Cycles in Northwestern South America: From the Iapetus to the Caribbean

Geosciences ◽

10.3390/geosciences12010005 ◽

2021 ◽

Vol 12 (1) ◽

pp. 5

Author(s):

Richard Spikings ◽

Roelant Van der Lelij

Keyword(s):

South America ◽

Passive Margin ◽

Large Igneous Province ◽

Geochemical Data ◽

Active Margin ◽

Iapetus Ocean ◽

Continental Arc ◽

Wilson Cycle ◽

The Caribbean ◽

Back Arc

Isotopic and geochemical data delineate passive margin, rift and active margin cycles in northwestern South America since ~623 Ma, spanning from the Iapetus Wilson Cycle. Ultramafic and mafic rocks record rifting associated with the formation of the Iapetus Ocean during 623–531 Ma, while the initiation of subduction of the Iapetus and Rheic oceans is recorded by continental arc plutons that formed during 499–414 Ma, with alternating compressive and extensional stages. Muscovite 40Ar/39Ar dates suggest there may have been a phase of Carboniferous metamorphism, although this remains tentative. A Passive margin was modified by active margin magmatism that started at ~294 Ma and culminated with collisional tectonics that signaled the final stages of the amalgamation of western Pangaea. Early Pangaea fragmentation included back-arc rifting during 245–216 Ma, leading to a Pacific active margin that spanned from 213–115 Ma. Trench retreat accelerated during 144–115 Ma, forming a highly attenuated continental margin prior to the collision of the Caribbean Large Igneous Province at ~75 Ma.

Download Full-text

Silurian-Early Devonian ostracodes from South America (Argentina, Bolivia): Preliminary investigations

Journal of Paleontology ◽

10.1017/s0022336000035265 ◽

1995 ◽

Vol 69 (4) ◽

pp. 752-772 ◽

Cited By ~ 12

Author(s):

J. M. C. Vannier ◽

P. R. Racheboeuf ◽

J. L. Benedetto

Keyword(s):

South America ◽

Lower Devonian ◽

San Juan ◽

South American ◽

Additional Material ◽

Lower Paleozoic ◽

Early Devonian ◽

The North ◽

Lower Ordovician ◽

South American Continent

Ostracodes are described from the “Cerro del Fuerte Section” and neighboring localities, all in the Precordillera de San Juan (northern Argentina, San Juan Province), and from sparse faunas in Bolivia (Chuquisaca, Tarabuco Province). Additional material comes from the collection of Thomas (1905). This preliminary study gives the first detailed description of ostracode assemblages in the Upper Silurian and Lower Devonian of the South American continent. Records of other abundant lower Paleozoic (Lower Ordovician to Lower Devonian) ostracodes in Argentina, Bolivia, Brazil, Peru, and Venezuela are also reviewed. Twelve different species, belonging to Palaeocopa (Beyrichiacea and Primitiopsacea) and to Binodicopa and Podocopa (Healdiacea, Thlip-suracea, Cypridacea) are described and a new genus is established (Australobollia n. gen.). Ostracode distribution at Cerro del Fuerte attests to the presence of the Siluro-Devonian boundary within the upper Los Espejos Formation and confirms recent stratigraphical attributions mainly based on conodonts and brachiopods (Benedetto et al., 1992). The beyrichiacean Hemsiella indicates a late Ludlow to Pridolian age for the lower part of upper Los Espejos Formation. The non-palaeocope “Thlipsurella-Phanasymmetria-Ranapeltis” assemblage found in the uppermost part of the formation indicates an Early Devonian (Lochkovian) age. The present study reveals the existence of faunal links at genus (Silurian) and probably species (Early Devonian) level between South America (Argentina, Bolivia), Laurentia, Avalonia-Baltica, and northern Gondwana. For example, close affinities (e.g., Ranapeltis sp. aff. rowlandi and Thlipsurella sp. aff. ellipsoclefta) exist between the uppermost Los Espejos Formation (Argentina) and contemporaneous horizons in the North American Mid-Continent (e.g., Haragan Formation, Oklahoma; Shriver Formation, Pennsylvania). Two types of ostracode assemblages, “beyrichiacean-dominated” and “thlipsuracean-bairdiacean-cypridacean dominated,” are recognized in the Late Silurian–Early Devonian of Argentina and discussed relative to other assemblages known in Laurentia, Avalonia-Baltica, and northern Gondwana. Their paleoecological significance in relation to marine bathymetry is addressed.

Download Full-text