A. adj. Geol. Applied to a line or axis towards which strata dip or slope down in opposite directions; also said of the fold or bend in such strata, or of a valley, trough, or basin so formed. Opposed to ANTICLINAL.
1833. Lyell, Princ. Geol., III. 293. A series of anticlinal and synclinal lines, which form ridges and troughs running nearly parallel to each other.
1863. Dana, Man. Geol., § 113. 105. A synclinal valley is a valley formed by strata sloping downward from either side.
1867. Murchison, Siluria, viii. (ed. 4), 171. The extension of the … Silurian strata … by … synclinal folds.
1876. Page, Adv. Text-bk. Geol., xix. 376. The synclinal basins of London and Hampshire.
b. transf. and gen. Inclined or sloping towards each other, or characterized by such inclination.
1880. B. E. Falkonberg, Desert Life, 320. Narrow avenues of airy palm-trees with their tops of synclinal fan-tracery.
1903. Agnes M. Clerke, Probl. Astrophysics, I. xi. 126. Synclinal forms (as the petal-shaped structures are called) emerge in both, and the branching effusions round the trapezium seem to mimic details legible in many eclipse-pictures.
B. sb. Geol. A synclinal line, fold, or depression.
1855. J. Phillips, Man. Geol., 142. The strata rising and falling in many steep anticlinals and deep synclinals.
1874. Raymond, Statist. Mines & Mining, 512. The east shaft … has passed the synclinal and is now cutting through the south-dipping strata.
Hence or so Synclinally adv., in the form of a synclinal fold; Syncline, a synclinal fold or depression; Synclinical a. = SYNCLINAL a.; ǁ Synclinorium, pl. -ia, anglicized Synclinore, see quots.; whence Synclinorial, -orian adjs.
1846. Worcester (citing Rogers), Synclinical.
1855. J. Phillips, Man. Geol., 45. The strata are synclinally and anticlinally bent.
1873. J. Geikie, Gt. Ice Age, xxi. 266. Diagrammatic view of synclines and anticlines.
1880. Dana, Man. Geol. (ed. 3), 821. The mountain range, begun in a geosynclinal, and ending in a catastrophe of displacement and upturning, is appropriately named a synclinorium.… (The word is from the Greek for synclinal, and ὄρος, mountain). Ibid., 823. After the last mentioned synclinorial range [of mountains] was completed. Ibid. (1883), Text-bk. Geol., 56 (Cent. Dict.) Synclinore.
1883. A. Winchell, World-Life (1889), 331. Geosynclinals are in progress beneath the sea, which will never attain synclinorian crises unless some revolution provides supplies of sediments.
1893. B. Willis, in 13th Ann. Rep. U.S. Geol. Surv., II. 219. The two great types of folds are the syncline and the anticline. The syncline … is a depression of the strata from a flat to a basin-shaped form.
