ABSTRACT
The middle Ordovician rocks of the Albany 15 minute quadrangle comprise
interbedded graywacke and shale, and in the east, coarse cobble or olistostromic
deposits. The detrital composition, westward fining and regional westward
transgression of these deposits indicate that these were sediments shed
off the westward thrusting Taconic Allochthon. Primary sedimentary structures
show that these rocks were deposited by turbidity currents flowing into
a longitudinal trough, probably formed in response to increased load during
overthrusting. Although strongly dependent on lithology, deformation intensity
generally increases from west to east; from essentially undeformed bedded
flysch through asymmetrically folded and thrust beds to highly deformed
melange containing isoclinally folded, transposed and boudinaged beds within
a phacoidally cleaved shaly matrix. Folds in the least deformed flysch
are generally open and have horizontal hinge lines. In more highly deformed
rocks folds are isoclinal with hinge lines plunging to the SE. This suggests
that with increased strains overturned folds in the flysch rotated into
the direction of maximum finite extension. This direction corresponds with
the overthrust direction indicated by slickenside striations on minor fault
planes. Fold development apparently occurred as a two phase progressive
event, with initiation of buckle folds followed by the development of extreme
noncylindrial hinge lines accompanying brittle failure and boudinage. Locally,
a third phase of folding has occurred. In addition, an early phase of chaotic
folding occurred within a chert and siliceous argillite unit. The formation
of the Taconic melange in this area can be explained through the progressive
disruption of a syndepositionally deformed turbidite fan complex, which
included coarse proximal or olistostromic facies. Additionally, thrusting
has led to the incorporation of slivers or klippes of older facies into
the melange.
Unpublished MSc. thesis, State University of New York at Albany.
151pp., +xi; 6 folded plates (maps)
University at Albany Science Library call number: SCIENCE Oversize
(*) QE 660 V65X
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