Searching for the root zone(s) of the Taconic allochthons: Leaving no stone unturned

Conference · Mon Mar 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5688530

Ratcliffe, N M ^[1]

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1. Geological Survey, Reston, VA (United States)

The site(s) of deposition and present location of the root zone(s) for the Taconic allochthon are major unresolved questions in Appalachian geology. The Green Mountain massif, the adjacent eastern cover sequence as well as extra-Laurentian sites have all been suggested. New geologic mapping, stratigraphic analyses, and geochemical studies of metabasalt sequences in Vermont redefine but do not solve the problem. If a single source area is assumed, the root zone is (1) not the Green Mountain massif as it lacks faults previously suggested, and therefore is not wide enough to accommodate the sediments of the allochthons, (2) outboard of the Cambrian shelf and shelf edge carbonates in the Tyson and Plymouth Formations but inboard of the Pinney Hollow Formation or Rowe Schist that contain abundant MORB, (3) probably outboard of the Chester dome because thrust faults that carry Pinney Hollow over the Hoosac Formation encircle the dome. However, the Hoosac and Pinney Hollow Formations contain alkalic to MORB basalts absent from the allochthons and they may be rift and predrift sedimentary rocks older than the bulk of the allochthon and therefore may not constrain source area. Additional uncertainty of root zone location comes from the fact that the eastern cover sequence is internally highly faulted and does not necessarily preserve either stratigraphic continuity or correct relative positions of the units. Despite the uncertainties listed above, striking similarities between rocks of the Dorset Mountain and Greylock slices with Hoosac lithologies now exposed at or near the eastern margin of the Green Mountain massif and on Hoosac Mountain, suggest these rocks were once coextensive. Rocks of the Chatham and Rensselaer Plateau slices have no counterpart in any exposed rocks and probably rooted outboard of Chester-Athens domes.

• OSTI ID: 5688530
• Report Number(s): CONF-9303211--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:2
• Country of Publication: United States
• Language: English

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58 GEOSCIENCES
580000* -- Geosciences
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CHEMISTRY
COMPARATIVE EVALUATIONS
DEPOSITION
DEVELOPED COUNTRIES
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GEOCHEMISTRY
GEOLOGIC FAULTS
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GEOLOGIC MODELS
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USA
VERMONT
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