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Taken collectively, the petrographic evidence for basement-contact relations overwhelmingly supports a tectonic contact in most locations, and an angular unconformity in one locality, Timber Brook.
The Warrensburg Sandstone Lies with angular unconformity upon cyclothemic rock units belonging to the Desmoinesian Series (Figures 3 and 4).
Third-stage deposits lie on the second-stage sediments with a slight angular unconformity and, moreover, the transition is marked by paleosol remnants.
The boundary with the Albarracin Formation is transitional, although as a result of its syntectonic deposition, the Mogna Formation also lies with an angular unconformity over the Albarracin Formation in the upper part of the fold limbs and on the Devonian succession in the anticlinal crest zone (Fig.
In many areas in the basin, an angular unconformity separates the base of the Cheverie Formation from underlying either Horton Bluff Formation or pre-Horton Group Devonian strata.
Besides these relationships, the general N-S trend of the La Premia Formation conglomerates and ignimbrites substantially differs from the more complex distribution of the Andacollo Group outcrops, due to their different deformation grade and the pronounced angular unconformity that separates them (e.g.
occurrence to the SW of Khojak Formation and overlying the Nisai Formation with angular unconformity, we believe that it may be Early to Middle Miocene.
Some researchers consider that, the basement of Qiangtang Basin is buildup by two-layers of Proterozoic metamorphic rocks, lower crystal --rigid basement , upper metamorphic --plastic basement , and middle angular unconformity (Wang GZ et al.2001; Wang CS et al.2001).
The PTB exhibits three types of contact according to the location, ranging from the central axis to the margins of the depositional area: i) disconformity overlain by quartz-conglomerate; ii) apparent transition; or iii) angular unconformity produced by intra-Permian tilting (Durand, 2006).
The basal conglomerates of the Ait Driss Member rest unconformably on Cambrian to Devonian folded metasediments, and locally, with an angular unconformity on Late Carboniferous sediments (Hmich et al., 2006).