ABSTRACT
The Taconic Allochthon contains rocks of Cambrian (?), Cambrian
and Ordovician age. It measures approximately 200 kilometers by 25
kilometers and is located in contiguous sections of New York,
Vermont, Massachusetts, and Connecticut. The rocks are
predominantly slates with lesser amounts of arenites, wackes,
limestone, chert, and conglomerates. All have been subjected to
chlorite or biotite grade metamorphism and two tectonic
deformations. The study area in central Washington County, New
York, contains most of the Taconic sequence, and because of both
natural and man-made exposure it is more accessible than most
other locations.
A lithostratigraphic column has been identified which has more
detail than any single previous version. Because of the already
excessive Taconic nomenclature pre-existing boundaries and names
have been retained wherever appropriate. However, two new
formations and four new members have been described and formally
introduced. Extensive literature research suggests this column can
be applied throughout the Giddings Brook Slice of the Allochthon
as a reference section.
Analyses of horizontal and vertical rock type distribution,
sedimentary structures, and coarse clastic sedimentary petrography
indicate a depositional environment which varies both laterally
and with time. The overall picture suggests intermediate depths,
moderate distance from shore, and a slope between source and
deposition site which is sufficiently steep to permit turbidity,
debris, and channel flows. Comparisons with segments of a modern
stable rifted margin indicates that only the upper and lower
continental rise can accommodate this sedimentological variety on
a comparable scale.
Map pattern scale structural observations were consistent with
previous work and showed that the major folds have an approximate
north strike and are overturned to the west. Regional slaty
cleavage is axial planar to these folds. Evidence of a second
tectonic deformation, seen only sporadically, consisted of
fracture or crenulation cleavage and associated folds. Even more
infrequent were examples of soft sediment deformation.
Jacobi, Louise D. 1977. Stratigraphy, Depositional Environment
and Structure of the Taconic Allochthon, Central Washington
County, New York. Unpublished MSc. thesis, State University of New
York at Albany.193pp +ix +2p. abstract; 4 folded plates (map,
sections, stratigraphy).
University at Albany Science Library call number: SCIENCE
Oversize (*) QE 146 W3 J23x
Delano MS thesis scanned
image pdf (15 MB)
Plate
1
- Geological Map (Taconic Allochthon near Granville NY)
(coloured outcrop map, scale
1: 12,000) - 19MB pdf file
Plate
2
- Geological Cross Sections (Taconic Allochthon near Granville
NY)
(coloured cross sections,
scale 1: 12,000) - 9MB pdf file
Plate
3
- Geological Columns (Taconic Allochthon)
(part coloured lithounit
stratigraphic thicknesses, scale 1: 1,200) - 10MB pdf file
Plate
4 - Historical comparative stratigraphic chart
(uncoloured lithounit-age
stratigraphic chart) - 2.4MB pdf file
Return to MS Theses completed in the Geological Sciences Program, University at Albany