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The Florence-Niagara terrane is an elongate fault-bounded block ∼ 10 km wide and 80 km long, composed of miogeoclinal assemblage lithologies, bounded on the north by a generally coherent miogeocline extending to the Superior craton, and on the south by a probably exotic, magmatic arc terrane. The Florence-Niagara terrane is composed of a collage of eight fault-bounded packets. All fault packets are characterized by faults that trend west to west-northwest, with a dominant west-northwest-striking, deeply dipping foliation. Elongation lineations plunge down the dip of foliations in all cases except in packet 1, where bulk extension locally parallels shallowly plunging fold axes, a probable product of superimposed strains. Fold axes are subhorizontal, or girdled in the mean foliation plane, or plunge steeply. Packets containing girdled fold axes probably were subjected to greater strain than were packets with subhorizontal fold axes. Steeply plunging fold axes are not easily explained, but they were, perhaps, formed by noncoaxial deformation. One of the packets contains a younger generation of folds formed during east-west shortening. Another packet contains folds associated with later strike-slip faulting. Convergence between the magmatic terrane and the miogeocline probably resulted in accretion of miogeoclinal sediments in the forearc area of the magmatic terrane. The Florence-Niagara terrane may represent such a zone of forearc accretion formed prior to, and during, collision, and thus it may be referred to as an accretionary complex.

The early Proterozoic Chocolay Group in the Lake Superior region is a cratonal sequence consisting of a basal unit overlain successively by quartzite, dolomite, and slate formations. Two regional depositional environments are described: (1) present-day structural troughs (Marquette, Menominee, and Felch, Michigan) show evidence of having sedimentary-basin precursors; and (2) other areas (Gogebic Range, Michigan) show evidence of sedimentation in platform settings. The basal unit in the Marquette and Menominee troughs is as much as 160 m thick and was probably deposited by alluvial processes. In the Gogebic Range, the basal unit is less than 10 m thick and resembles lag deposits at the base of transgressive sequences. The overlying quartzite contains cross-beds that show two regional sedimentary-vector (paleocurrent) distributions: (1) unimodal low-variance distributions with sedimentary vectors oriented subparallel to local structural trough axes (Marquette, Menominee, and Felch troughs); and (2) polymodal distributions with sedimentary vectors showing greater dispersion about the mean (Gogebic Range). As indicated by many varieties of sedimentary structures (silicified evaporites, cryptalgal structures, intraclast breccias, and so on), the carbonates and interstratified siliciclastics of the Chocolay Group were deposited in subtidal to supratidal conditions. Taylor noted, in 1972, that certain members of the Chocolay Group carbonates thicken toward the center of the Marquette trough, with concomitant facies changes. The uppermost pelite unit of the Chocolay Group was probably deposited below normal wave base. It is concluded that the basins and platforms were formed on a craton undergoing rift-type tectonism.

This is the second of a series concerning the accretionary complex that is exposed on the island of Barbados and is thought to represent the Lesser Antilles fore-arc at its structural high. Two principle tectonostratigraphic elements are present in the Bissex Hill area: a basal complex composed of east-northeast–striking, generally steeply dipping, fault-bound packages of terrigenous sandstones and mudstones (mostly turbidites), hemipelagic rocks and melange; that complex is overlain by the Bissex Hill nappe, composed of calcareous pelagic rocks, crystalline limestone and foraminiferal arenite. Also present in the basal complex are smaller fault-bound packages, termed “micropackets,” composed of brecciated basal complex lithologies. Basal complex faults are cut by the Bissex Hill nappe, except on the southern margin of the Bissex Hill nappe where melange and hemipelagic lithologies apparently have been faulted over the nappe rocks. This youngest faulting may be driven by Holocene and older melange diapirism. Structural evolution of terrigenous and probably hemipelagic rocks in basal complex fault-packages is characterized by coaxial deformation about southwest-trending axes. Melange packages possibly experienced greater strain as evidenced by girdled fold axes and axial planes and foliations of constant orientation. Packet-bounding faults probably developed during early folding and probably represent surfaces against which packet contents contracted. Micropackets are the result of motions after the assembly of major packets, and are formed through fault imbrication and (or) diapiric injection. Rocks of the Bissex Hill nappe experienced folding first about a north-trending axis, followed by folding about a southwest-trending axis and gentle folding on the entire nappe about an east-northeast–trending axis. Deformation in the basal complex is thought to have occurred by progressive accretion of sediment packets. The Bissex Hill nappe is thought to represent a fore-arc basin complex thrust over the accretionary complex. Quartzose sandstones present in the Bissex Hill nappe that probably had their source in the basal complex indicate that the accretionary complex probably shoaled by the Miocene.