The lower Rocky Mountain Supergroup of Pennsylvanian age contains five formations which in ascending order are: Todhunter, Tyrwhitt, Storelk, Tobermory and Kananaskis. All except the Kananaskis are new formations that are equivalent to the Tunnel Mountain Formation. The Todhunter, Tyrwhitt and Tobermory consist mainly of brown weathering, dolomitic and quartzitic, very fine- to fine-grained, pure, quartz-chert sandstones with some interbedded, locally f ossiliferous, sandy dolomite. The Storelk is quartzitic, very fine- to medium-grained, very massive, cross-bedded, white wheathering quartzi-chert sandstone. All these formations contain varying amounts of scattered medium and coarse sand. The Kananaskis consists of sandy and cherty, dense, microcrystalline, grey dolomite. The Todhunter, Tyrwhitt and Storelk Formations are interpreted as being Early Pennsylvanian (Morrowan) in age, and the Tobermory and Kananaskis Formation, which regionally may be facies equivalents, as early Middle Pennsylvanian (Atokan) in age. The contact between the lower Rocky Mountain and the underlying Etherington Formation (Late Mississippian Chesterian) is conformable and locally gradational. Contacts between the Todhunter and Tyrwhitt, and between the Storelk and Tobernory are unconformable, whereas that between the Tyrwhitt and Storelk may be conformable or unconformable. The lower Rocky Mountain is unconformably overlain by Permian, Triassic or Jurassic strata. The lower Rocky Mountain sediments were deposited in a structural basin which may have been partially isolated from adjacent basins to the north, west and south by low barrier arches. Individual formations in the succession thin in a northwesterly and southwesterly direction towards the basin flanks, where as little as 160 feet of the five formations was deposited and remains, whereas at least 1,175 feet of equivalent strata is preserved in the central part. The quartz sand was probably transported by rivers and longshore marine currents from a source lying to the east within the continental interior. Chert and phosphorite fragments ranging up to pebble size were probably locally derived. The strata of Chesterian and Morrowan age represent a regressive sequence. After Morrowan time, gentle warping, emergence, and erosion caused truncation of Lower PennsyIvanian and Upper Mississippian strata towards the east. Angular truncation, and local conglomerates composed of chert, phosphorite, sandstone and dolmite granules and pebbles mark this unconformity. Strata of Atokan age thicken westward and represent a transgressive, sequence which onlaps and truncates the underlying strata. The Pennsylvanian sandstones are a potential source of pure silica sand. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

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Call number: LD2668 .T4 1978 M37 / Master of Science

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Conodontes são microfósseis potencialmente úteis para bioestratigrafia e em reconstruções paleoecológicas de rochas sedimentares paleozóicas e do Triássico. Desta forma, este estudo apresenta a classificação taxonômica e o estabelecimento das condições biocronoestratigráficas e paleoecológicas nas quais estes organismos viveram, bem como uma revisão do estágio atual do conhecimento a respeito dos conodontes e de seu aparelho alimentar. A seção analisada pertence à Formação Itaituba, Grupo Tapajós, Pensilvaniano da Bacia do Amazonas. A área de estudo localiza-se a Nordeste da cidade de Itaituba, às margens do Rio Tapajós, em um afloramento da Pedreira Calminas. A distribuição dos conodontes reconhecida define duas biozonas: uma Zona de Amplitude Diplognathodus orphanus e uma Zona de Concorrência Idiognathodus incurvus-Idiognathoides sinuatus. As espécies Diplognathodus coloradoensis, Diplognathodus orphanus e Idiognathodus incurvus formam uma associação tipicamente atokana. Baseando-se na associação descrita, a seção analisada foi definida como atokana. A espécie de melhor resolução bioestratigráfica é Diplognathodus orphanus, sendo sua distribuição restrita ao Atokano. O ambiente deposicional dominante na Bacia do Amazonas durante o Pensilvaniano é caracterizado por uma rampa carbonática rasa. Os depósitos estudados refletem uma sequência predominantemente regressiva, com a presença de gêneros de águas mais rasas, tais como Adetognathus, Diplognathodus e Ellisonia. A ocorrência de conodontes associados a braquiópodes, briozoários, crinóides e fragmentos de peixes sugere que estes estratos foram depositados em paleoambiente marinho raso, com energia de sedimentação baixa a moderada, em águas calmas, límpidas e quentes. No regime de flutuações de alta freqüência do nível do mar, os principais ambientes deposicionais eram laguna (submaré) e planície de maré (intermaré superior-supramaré inferior com tapetes microbiais). / Conodonts are useful microfossils for biostratigraphy and paleoecological reconstructions in Paleozoic and Triassic sedimentary rocks. This research aims to their taxonomic classification and to establish the biochronostratigraphic and paleoecological conditions in which these organisms lived. Furthermore, this study reviews the current knowledge about conodonts and their feeding apparatus. The section analyzed belongs to Itaituba Formation, Tapajos Group, Pennsylvanian of the Amazon Basin. The study area is located northeast of Itaituba city, on the banks of the Tapajós River, in an outcrop of Calminas Quarry. The distribution of conodonts recognized defined two biozones: Diplognathodus orphanus Amplitude Zone and Idiognathodus incurvus-Idiognathoides sinuatus Competition Zone. The species Diplognathodus coloradoensis, Diplognathodus orphanus and Idiognathodus incurvus are typically an Atokan association. Based on the association described, the section analyzed was defined as Atokan. The specie with better biostratigraphic resolution is Diplognathodus orphanus, because its distribution is restricted to the Atokan. The depositional environment prevailing in the Amazon Basin during the Pennsylvanian is characterized by a shallow carbonate ramp. The deposits studied reflect a predominantly regressive sequence, with the presence of shallow water genera, such as Adetognathus, Diplognathodus and Ellisonia. The occurrence of conodonts associated with brachiopods, bryozoans, crinoids and fish fragments suggests that these strata were deposited in a shallow marine environment, with low to moderate energy, in calm, clear and warm waters. In high frequency sea level fluctuations regime, the main depositional environments were lagoon (subtidal) and tidal flat (upper intertidal-lower supratidal with microbial mats).

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