171 Tectonics (Posters)

CROSS SECTIONAL INTERPRETATION OF THE TECTONIC HISTORY OF THE HAMBURG 7.5' QUADRANGLE, SUSSEX COUNTY, NEW JERSEY

Paper number: 171-4
Program: Technical Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

Neoproterozoic Laurentian crystalline basement, Cambrian-Ordovician carbonate passive margin and Ordovician Taconic clastic wedge rocks have been mapped in the Hamburg 7.5' Quadrangle, Sussex County, New Jersey. The southwest plunging Crooked Swamp syncline (Herman and Monteverde, 1989) has an up-plunge termination in the Hamburg quadrangle and the fold limbs are cut by normal and thrust faults. Normal faults are mapped in the eastern part of the quadrangle where Neoproterozoic crystalline basement and outliers of Cambrian-Ordovician carbonate rocks crop out on the surface. Synthetic and antithetic thrust faults are mapped in the central and western parts of the quadrangle with tip lines exposed in Cambrian-Ordovician carbonate and siliclastic rocks.

Balanced cross sections were constructed for the Hamburg 7.5' Quadrangle conserving line length, cut-off angles and stratigraphic thickness. Stratigraphic thickness interpretations are the result of detailed (1:250 scale) stratigraphic section measurement conducted during geologic mapping. Interpretation of stratigraphic contacts at depth is constrained by gas well data (Saunders, 1983) and seismic profiles (Herman, 1992). The cross sections are retro deformed from present-day deformed state to the undeformed passive-margin carbonate platform. The basal decollement is interpreted as displacing a folded Neoproterozoic crystalline basement. Paleozoic normal and/or thrust faults splay up section from the basal decollement. Cross-cutting relationships between a folded basement complex, an undeformed decollement horizon and thrust faults branching from the detachment horizon indicates the need to reconsider timing of deformation in the Hamburg 7.5' Quadrangle.