The Providence Island Formation in the northern Appalachian Region - a Lower-lower Middle Ordovician analogue to recent arid-semiarid tidal-flat carbonates of the Persian Gulf Trucial Coast

• Main Author: Roma Hernandez, Mauricio
• Format: Text
• Language: unknown
• Published: Scholars Archive 1987
• Subjects: Providence Island Formation; stratigraphic correlations; diagenesis; depositional environments; Geology; Stratigraphy; Newfoundland
• Online Access: https://scholarsarchive.library.albany.edu/cas_daes_geology_etd/76; https://scholarsarchive.library.albany.edu/context/cas_daes_geology_etd/article/1075/viewcontent/romamstxt.pdf

The Providence Island Formation of Early-early Middle Ordovician age occurs in the Champlain Valley and adjacent areas in eastern New York, western Vermont, and southern Quebec. The unit forms part of a carbonate shelf sequence which occupied the eastern margin of the North American continent from Newfoundland to Alabama, and its lithology is representative of the dolostone lithofacies that characterizes the uppermost Beekmantown Group in this region. This is the first study documenting depositional environments, diagenesis, and stratigraphic correlations of the Providence Island Formation. This formation consists, in decreasing abundance, of dolostones, limestones, shales, and dedolostones. The dominantly fine grain size of the rocks as well as the presence of sedimentary and diagenetic features such as homogeneous and mottled structures (biogenic), stromatolites, mudcracks, herringbone cross-bedding, fenestral cavities, evaporites or their pseudomorphs, diapiric structures, and solution-collapse breccias indicate that these sediments record tidal flat paleoenvironments. These are low tidal flat, high tidal flat and, to a lesser extent, subtidal and supratidal settings similar to those existing in modern arid, restricted marine tidal flats of the Persian Gulf Trucial Coast. The lithofacies and their inferred setting include: (1) Homogeneous dolostone: subtidal to lower intertidal or, occasionally, supratidal (sabkha). (2) Homogeneous limestone: lower intertidal. (3),(4) Mottled dolostone/limestone: lower intertidal. (5),(6) Laminated dolostone/limestone: upper intertidal. (7) Skeletal limestone: mostly upper intertidal. (8) Dedolostone: mostly upper intertidal to supratidal. (9) Shale: subtidal-lower intertidal to supratidal. Most laminated dolostones and limestones represent stromatolites. On the basis of composition and texture, the alternating laminae are grouped into two types: - Dolomitic facies: (I) FM-CPA: (F-fine, M-matrix – C-coarse, P-pyritic, A-allochemical-terrigenous) and (II) F-CA. - Calcareous ...