Post-Paleozoic activity - Lamont-Doherty Earth Observatory ...

330 W. Manspeizer and Others
USGS LINE 28 NORFOLK BASIN
^00 500 600 700 800 900 1000 1100 1200
"
Figure 9. Seismic record of part of USGS line 28 showing buried Norfolk basin (shotpoints 500 to
1,000). Diffractions obscure some of the deeper reflectors. Upper limit of northwestdipping units in
basin is truncated by the postrift unwnformity (PRU). Caption and figures from Klitgord and Hutchin-
son 91985).
northwest-southeast extensional strain increased, new northeast-
trending faults (with evidence for dip slip and oblique slip) devel-
oped. These later faults were reactivated by sinistral strike slip
following emplacement of lava flows in the Early Jurassic. Dip-
slip motion in all cases preceded strike-slip and oblique-slip; and
in most cases, northeast, north-northeast, and east-northeast faults
cut north-south faults. Normal faulting resumed in the late phases
of basin formation and was followed by Cretaceous(?) compres-
sion, in which the region was alternately deformed by northeast-
southwest and northwest-southeast compressive forces.
The general homoclinal character of synrift strata within the
exposed basins thus belies their complicated structural histories.
TERTIARY 1
Although each basin has unique features, they share a core of
stratigraphic and structural elements that allow us to model, for
example, the Newark basin (Fig. 6) of New Jersey and Pennsyl-
vania, which geologically is the best known of these basins.
By analogy with the Atlantis and Long Island basins (Figs.
7, 8), the Norfolk and Franklin basins (Figs. 9 and lo), the
Hartford-Deerfield basin (Ando and others, 1984), the Rich-
mond and Taylorsville basins (Ressetar and Taylor, 1988), and
the Culpeper basin (Costain and others, this chapter), we model
the Newark basin as a half graben with west-dipping strata and
with listric normal border faults that sole into east-facing detach-
ment surfaces of thrust-imbricated Precambrian and Paleozoic
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