Abstract Detailed mapping and logging of successions in the Central Inlier of central Jamaica has been undertaken. The succession contains three angular unconformities that allow the division of the succession into four units. The oldest rocks, the Arthurs Seat Formation, consist of a lower series of tholeiitic basaltic lavas and an upper unit of poorly sorted conglomerates with some calc-alkaline lavas. They represent lavas and proximal volcaniclastic deposits of a late early or early late Cretaceous volcanic center. The late Santonian to early Campanian Crofts Hill Synthem (Peters Hill Formation, Back River Formation [new], and Dawburns Content Formation [new]) rests unconformably on the Arthurs Seat Formation. It represents a deepening-upward succession, beginning with rudist limestones and ending in turbiditic sandstones and shales. The unconformity at the base of the Crofts Hill Synthem is interpreted as the result of a rifting event that created an intra-arc to back-arc basin, in which the rocks of the Crofts Hill Synthem were deposited. The Crofts Hill Synthem is cut by late Campanian thrust faults that dip toward the north. This thrusting was caused by the collision of the western part of the Greater Antilles arc with the Yucatán Peninsula. The Maastrichtian Kellits Synthem represents a transgressive-regressive cycle that rests unconformably on the rocks of the Arthurs Seat Formation and Crofts Hill Synthem. The succession begins with braided stream deposits (Slippery Rock Formation) and passes upward through tidal-flat siltstones (Thomas River Formation) into open-shelf limestones (Guinea Corn Formation). The succeeding Summerfield Group represents a progradational volcaniclastic braid-plain delta complex (Green River, Peckham, and Mahoe River Formations) and is succeeded by a thick succession of ignimbrites (Waterworks Formation). The volcaniclastic sediments and ignimbrites are interpreted to have been shed from a newly emergent volcanic center in eastern Jamaica, possibly the Above Rocks magma chamber. The Kellits Synthem is overlain unconformably by the limestones and clastics of the middle Eocene Yellow Limestone Group. This unconformity is interpreted to represent the initiation of northeast-southwest-directed extension that saw the formation of the Wagwater Trough in eastern Jamaica.

Abstract The Tertiary sedimentary and volcanic rocks of the Cascade Range unconformably overlie a crystalline basement of previously accreted terranes. The Tertiary strata are parts of four synthems, or interregional unconformity-bounded sequences of tectonic origin. Thus, the formations in these synthems were not deposited in local basins. The 55-38 Ma Challis synthem has five regional unconformity-bounded formations; the names with precedence are (from the base up) Swauk, Taneum, Teanaway, Roslyn, and Naches. Near Blewett Pass (nee Swauk Pass), the Challis fluvial and arkosic Swauk Formation is ~5 km thick and has several members in a generally upward-fining succession. The members of the Swauk do not interfinger, and some are separated by unconformities. The Oligocene to mid-Miocene andesitic and rhyolitic Kittitas synthem is almost absent in the area. The most voluminous lithostratigraphic unit in the mid-Miocene to Pliocene Walpapi synthem is the Columbia River Basalt Group. Clasts of Columbia River Basalt Group and older rocks in the ca. 4 Ma Thorp Formation of the High Cascade synthem record initial uplift of the Cascade Range to the west. North of Blewett Pass, the northwesterly segment of the Leavenworth fault is the Camas Creek reverse fault that places Swauk and Teanaway in the Blushastin anticline over a syncline in the Roslyn Formation. Northerly striking faults in the Leaven-worth fault zone are parts of a younger system that cuts the Camas Creek thrust and northwest-striking folds in Challis rocks. In style, scale, and age, the Camas Creek fault resembles the Easton Ridge thrust south of Cle Elum, the Eagle Creek fault in the Chiwaukum graben, and the Seattle fault in the Puget Lowland. These faults are on the steeper northeastern limbs of major anticlines in Challis rocks. Down plunge, these folds are more gentle in Walpapi rocks. These folds and faults are part of the regional Seattle-Wentachee-Kittitas fold-and-thrust belt. The Straight Creek fault is a major, north-south, dextral fault in the northern Cascade Range. The fault offsets all five of the Challis unconformity-bounded formations. The southeasterly curving discontinuity along which it was mapped east of Easton is due to unconformities at the base of the Taneum and Teanaway, not a fault. The Straight Creek fault is 2.7 km west of Easton and passes southward beneath Kittitas rocks. Although the fault dextrally displaces pre-Tertiary units >90 km, Tertiary displacement is &55 km. This may indicate two (or more) periods of displacement. Perhaps the displaced portion of the fault underlies Puget Sound. Two sets of post-Walpapi folds deform the Tertiary synthems. The Seattle-Wentachee-Kittitas fold-and-thrust belt is part of a set of northwest-striking folds. One of several north-trending regional anticlines causes the Cascade Range. The Cascade Range anticline, with an amplitude of ~3.5 km, has risen in approximately the past 3.5 m.y. This anticline causes the plunges of the Seattle-Wentachee-Kittitas fold-and-thrust belt folds. The two sets of folds cause a regional interference, or “egg-crate,” pattern that dominates the present topography of the Pacific Northwest.