George W. Grader

Permian marine sedimentation in northern Chile: new paleontological evidence from the Juan de Morales Formation, and regional paleogeographic implications

Abstract Permian marine sedimentary rocks that crop out in northern Chile are closely related to the development of a Late Paleozoic magmatic arc. A study of Upper Paleozoic units east of Iquique (20°S) identified three members within the Juan de Morales Formation, each of which were deposited in a different sedimentary environment. A coarse-grained terrigenous basal member represents alluvial sedimentation from a local volcanic source. A mixed carbonate-terrigenous middle member represents coastal and proximal shallow marine sedimentation during a relative sea-level rise related with a global transgression. Preliminary foraminifer biostratigraphy of this middle member identified a late Early Permian (late Artinskian–Kungurian) highly impoverished nodosarid–geinitzinid assemblage lacking fusulines and algae, which is characteristic of temperate cold waters and/or disphotic zone. The upper fine-grained terrigenous member represents shallow marine siliciclastic sedimentation under storm influence. The Juan de Morales Formation consists of continental, coastal and shallow marine sediments deposited at the active western margin of Gondwana at mid to low latitudes. A revised late Early Permian age and similar paleogeography and sedimentary environments are also proposed for the Huentelauquen Formation and related units of northern and central Chile, Arizaro Formation of northwestern Argentina, and equivalent units of southernmost Peru.

The palynology of the Lower Permian (Asselian-?Artinskian) Copacabana Formation of Apillapampa, Cochabamba, Bolivia

The palynostratigraphy of the lower and Coal members of the Copacabana Formation from Apillapampa, central Bolivia was investigated. Twelve samples yielded abundant and diverse, moderately well-preserved pollen and spores. One new spore species, Dictyotriletes cousmineri, is described and 52 species are recorded for the first time in Bolivia. Two species each of acritarchs and scolecodonts are also present. The lowermost assemblage yielded Vittatina and taxa such as Pakhapites ovatus and Marsupipollenites striatus, which are characteristic of the Asselian—Early Artinskian Vittatina costabilis Zone of the Paraná Basin, Brazil. The uppermost assemblage is defined by the appearance of several species of Lueckisporites, together with species of Vittatina, Lunatisporites, Pakhapites, Hamiapollenites, Corisaccites, Mabuitasaccites, Striomonosaccites, Striatoabieites, Striatopodocarpites and Weylandites. Abundant monolete and trilete spores with subordinate pollen grains are present in the Coal Member. Those species suggest correlation to the Middle Artinskian—Wuachiapingian Lueckisporites virkkiae Zone of the Paraná Basin. Highly variable associations of gymnosperms occur in the lower member whereas pteridophytes, sphenophylls and lycopods are dominant in the overlying Coal Member. These groups of plants characterised terrestrial landscapes along marine margins during the Early Cisuralian, and confirm the widespread distribution of the Glossopteris flora during the Permian in Gondwanaland. Preliminary radiometric data from interbedded tuffs suggest an Asselian—Sakmarian age for the marine Copacabana Formation and a Sakmarian—?Artinskian age for the overlying Coal Member. These new data are highly significant in terms of Permian correlations in central South America.

Global biostratigraphic comparison and correlation of an early Cisuralian palynoflora from Bolivia

This paper presents new data about Early Permian (Cisuralian) strata, palynostratigraphy and absolute dating from the Copacabana Formation in central Bolivia. Recent stratigraphic and palynologic data from marine and transitional rocks at Apillapampa refine the age of Cisuralian palynomorphs in South America. Twelve samples interbedded with five volcanic ashes (processed and productive) yielded 94 palynomorph species arranged in two informal palynoassemblages: the lower assemblage Vittatina costabilis corresponds to one sample near the base of the Copacabana Formation and the upper Lueckisporites virkkiae assemblage occurs in overlying marine and coal-bearing transitional intervals. Ages were also independently refined by a modern review of conodonts, fusulinids, along with those U–Pb radiometric ages (Isotope Dilution Thermal Ionization Mass Spectrometry [ID-TIMS] of zircon-bearing interbedded tuffs). These data suggest that the lower marine member of the Copacabana Formation at this location is Asselian and Sakmarian. Lueckisporites virkkiae is a key species of palynomorph utilised in South American and global Permian biostratigraphic reconstructions. Hence, a thorough global comparison of these palynofloras and correlations is addressed in this contribution, considering first appearances of mainly cosmopolitan diagnostic taxa. Correlations are established with many similar Permian palynofloras, some also constrained with radiometric data, in South America (Brazil, Uruguay and Argentina) and elsewhere.

Permian plants from the Chutani Formation (Titicaca Group, northern Altiplano of Bolivia): II. The morphogenus Glossopteris

Fossil plants belonging to the morphogenera Glossopteris, Pecopteris and Asterotheca were collected from the upper part of the Chutani Formation (Titicaca Group), near the town of San Pablo de Tiquina, on the southeastern shore of Lake Titicaca (northern Altiplano, Bolivia). This paper presents the first description of specimens of the morphogenus Glossopteris from Bolivia. The Bolivian specimens of Glossopteris consist of poorly-preserved impressions, although they present the diagnostic features of this morphogenus. They are fragments of leaves with secondary veins of taeniopterid-type, typical of glossopterids from Late Permian deposits of Gondwana. The only species ofPecopteris confirmed in the first part of this study, i.e. P.dolianitii Rosler and Rohn (see Vieira et al. 2004), was previously reported from the Late Permian beds of the Rio do Rasto and Estrada Nova formations in the Parana Basin (southern Brazil). Therefore, a Late Permian age is proposed for the fossil plant-bearing beds of the Chutani Formation based on the analyzed assemblage. The phytogeographic implications of this new find are briefly analyzed.

Permian plants from the Chutani Formation (Titicaca Group, Northern Altiplano of Bolivia): I. Genera Pecopteris and Asterotheca

Fossil plants belonging to the morphogenera Glossopteris, Pecopteris and Asterotheca were collected from the upper part of the Chutani Formation (Titicaca Group), near the town of San Pablo de Tiquina, on the southeastern shore of Lake Titicaca (northern Altiplano, Bolivia). Here we report the analysis of fern-type foliage found at this location. Three species of pecopterid fronds are identified: Pecopterisdolianitii Rohn and Rosler, P. cf. P. cadeadensis Rohn and Rosler, and P. cf. P. pedrasica Read. All these species are typically found in Permian deposits of the Parana Basin in southern Brazil. Despite the poor preservation of the material, a fertile specimen could be studied and was determined asAsterotheca sp. The paleoenvironmental and paleoecological implications of this new find are briefly analyzed.

Palynologic delineation of the Devonian–Carboniferous boundary, West-Central Montana, USA

ABSTRACT Cratonic depositional systems in the Central Montana Trough involve the Devonian--Carboniferous boundary (DCB), and reflect both subtle regional epeirogeny and significant global glacioeustatic controls. A palynologic analysis of the upper Three Forks, Sappington and lower Lodgepole formations was carried out at the classic Logan Gulch location in Horseshoe Hills. The lower Trident Member of Three Forks Formation yielded low-diversity cosmopolitan, long ranging phytoplankton and few spores species (LAs1), attributed to the middle Famennian. The upper part of the same green seaway shale yielded only leiosphaerids and Botryococcus (LAs2), along with an external mold of a clymenid ammonoid. Age-diagnostic spores Retispora lepidophyta, Verrucosisporites nitidus and Vallatisporites vallatus from middle Sappington siltstone (LAs3) indicated a Strunian LN Zone. Two more assemblages from upper Cottonwood Canyon Member (LAs4) and false Bakken (LAs5), in the lower Lodgepole Formation yielded scarce, poorly preserved spores. The presence of Waltzispora polita in LAs4 indicated a Tournaisan-Visean age.

Biostratigraphic Significance of Lower Cisuralian Palynoflora from Apillapampa, Bolivia

Recent stratigraphic and palynological data from marine and transitional rocks of the Copacabana Formation at Apillapampa in central Bolivia refine the age of Cisuralian palynomorphs in South America. Samples interbedded with volcanic ashes yielded palynomorph taxa arranged into two informal palynoassemblages: the lower assemblage Vittatina costabilis (Vc) occurs in one sample at the base of the Copacabana Formation, and the upper Lueckisporites virkkiae (Lv) assemblage is found in overlying marine and coal-bearing transitional intervals. Ages were also independently refined by a modern review of microfossil (conodonts and fusulinids) and five U–Pb radiometric ages (ID–TIMS of zircon-bearing interbedded tuffs), which confirm that the Copacabana Formation at this location is Asselian and Sakmarian in age. Lueckisporites virkkiae and other palynomorphs are key species of palynozones utilized in South American and global Permian biostratigraphic reconstructions. Hence, a thorough global comparison of these palynofloras and correlations is made in this study, considering the first appearances of mainly cosmopolitan diagnostic taxa. Correlations are established with many similar Permian palynofloras, some also constrained by radiometric data, in South America (Brazil, Uruguay, and Argentina) and elsewhere (Africa, Australia, Oman, and Saudi Arabia).