Isoclinal fold

The Tisdale rocks were deformed by two tectonic events that resulted in superposition of east-west isoclinal folds on older north-south open folds. Five camp- to regional-scale faults, including the Hollinger Shear Zone (HSZ), have offset all these rocks. The HSZ is a reverse fault ( 140 m offset) that passes through the Hollinger-Mcintyre mine, strikes 57°, dips 65°S, extends to a depth of >1,500m and formed synchronous with the east-west folds. Most gold mineralization in the HMC deposit is associated with rocks in and above the HSZ. 

Structural studies by Zwanzig (1999) identified five episodes of deformation in the south flank of the Kisseynew Domain, four of which are evident in the Sherridon Complex. An episode of Fi isoclinal folding has been recently hypothesized... 

The four phases are Di thrust-related tight to isoclinal (Fi) folds and associated axial planar schistosity (Si). D2 tight-to-isoclinal folds (F2), with S2, are interpreted as high strain deformation with F1/F2 fold interference structure (Fig. 6) resulting in the development of SI/S2 composite fabric elements. D3 are recumbent and best developed in the west part of the BMC, and D4 are represented as kink-folds. 

Figure 27 Occurrences of isoclinally folded and boudinaged mafic layers in the Beni Bousera otogenic peridotite, northern Morocco, after Allegre and Turcotte, 1986 reproduced by permission of Nature Publishing Group from Nature, 1986, 323, 123-127. In their marhle cake model, Allegre and Turcotte interpret these mafic layers as subducted oceanic lithosphere—modified by partial melting and metamorphism—that was stirred, stretched, and thinned by mantle convection (see, also, Kornprobst et al., 1990 Blichert-Toft et al., 1999). For Pearson et al. (1993), these pyroxenites would rather derive from crystallization products of partial melts from subducted crust. They would have been emplaced as dikes in the hanging wall of a subduction zone and deformed during the exhumation of the...

The basement rocks of the Patuxent Range in Fig. 8.7 consists almost exclusively of the isoclinally folded metasedimentary rocks of the Patuxent Formation (redefined) and are not interbedded with felsite and basalt flows but they are cut by thin porphyritic... 

Fig. 8.7 The Patuxent Range forms the most southerly part of the Pensacola Mountains. It consists of nunataks composed of the Patuxent Formation (as revised by RoweU et al. 2001) which forms the local basement complex. The metasedimentary rocks of the Patuxent Formation are isoclinally folded and consist of a repetitious sequence of graywacke and slate. These rocks are younger than the fossiliferous Nelson Limestone which is late Middle Cambrian. The map area also contains outcrops of Devonian sandstone south of the Patuxent Range and of Permian siltstone and shale of the Pecora Formation in the Pecora Excarpment (Adapted from Schmidt and Ford 1969 with information from Rowell et al. 2001)...

Fig. 8.8 The basement rocks of the Neptune Range in the Pensacola Mountains consist of the isoclinally folded metasedimentary rocks of the Hannah Ridge Formation (defined by Rowell et al. 2001) which is unconformably overlain by the Nelson Limestone (late Middle Cambrian) followed by the Gambacorta Rhyolite and the Wiens Formation (Cambro-Ordovician). These basement rocks were locally intruded by the Serpan Granite and by the hypabyssal Mount Hawkes Porphyry. The Paleozoic sedimentary rocks include the Gale Mudstone which is a trUite of Permian age which resembles the Buckeye Tillite of the Beacon Supergroup in the Ohio Range of the Horlick Mountains (Adapted from Schmidt and Ford 1969 with information from Stump 1995)...

If beds that are horizontal, or nearly so, suddenly dip at a high angle, then the feature they form is termed a monocline (Fig. 2.4c). When traced along their strike, monoclines may flatten out eventually or pass into a normal fault indeed, they often are formed as a result of faulting at depth. Isoclinal folds are those in which both the limbs and the axial plane are parallel (Fig. 2.4d). A fan fold is one in which both limbs are folded (Fig. 2.4e). 

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