Lower Ordovician

Lower Ordovician

[′lō·ər ‚ȯr·də′vish·ən]
(geology)
The earliest epoch of the Ordovician period of geologic time, extending from about 490- to 460,000,000 years ago.
References in periodicals archive ?
The description of the 33 m deep Varudi borehole in the sector B2 is unique: Lower Ordovician sandstones, shales and clays are covered by Late Pleistocene till (27 m) and Holocene peat (3 m), whereas the typical Middle Ordovician limestones found in the neighbouring boreholes are missing (Suuroja et al.
El-Franig produces from Lower Ordovician Hamra sands at a depth of 3,950 m.
The Maigaiti slope is based on the weathered crust of the Middle and Lower Ordovician Yingshan formations.
Peter Sandstone and the Upper Cambrian and Lower Ordovician Jordan Formation, with the Upper Cambrian Wonewoc and Mount Simon Formations gaining in importance.
The company added that Cat-1 will be drilled to a depth of 3,850 metres to evaluate the Lower Ordovician Hamra and El Atchane sandstone reservoirs.
Single kukersite seams are found in the Lower Ordovician Kunda Stage.
The target was composed of the stratified sedimentary cover comprising (from the top) bedded Upper and Middle Ordovician limestone (up to 20 m thick), Lower Ordovician Dictyonema shale (argillite with an admixture of organic matter, about 2 m thick), and an up to 200 m thick layer of Lower Ordovician to uppermost Vendian sand, silt, and some clay, which covered the Precambrian basement consisting of granites, gneisses, amphibolites, and other crystalline rocks.
The serpentinite occurs as pods and lenses in the Missisquoi Formation, a metamorphic complex in Vermont assigned to the Lower Ordovician.
This study examined the kinematics of strata in a 100-m-long roadcut on Highway 5 twelve miles north of Lebanon, where the upper part of the lower Ordovician Jefferson City Dolomite crops out in a structurally depressed zone.
The next westerly occurrence of Lower Ordovician felsic volcanic rocks lies several kilometres to the west of the southern extension of the Otter Slide belt, in the headwaters of Napadogan Brook (Lutes 1981), outside of the Napadogan area discussed here.
The territory is composed of Cambrian terrigenous sediments, lower Ordovician spilite-diabase sequences and middle-upper Ordovician sandstones and shales.