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

Strata within these Mesozoic basins are also cut by major
oblique-trending cross faults, Sanders (1963) reports that in the
Newark basin some faults have as much as 20 km of horizontal
displacement and 3 km of vertical displacement, and Van Houten
(1969) reports that some northeast-trending strike-slip faults in
the Newark basin may be part of a strike-slip system involving
the Ramapo border fault (Fig. 5). Published geophysical and
subsurface data from the Newark-Gettysburg basin (Sumner,
1977; Cloos and Pettijohn, 1973), the Hartford basin (Wenk,
1984), the Durham basin (Bain and Harvey, 1977), and the
Sanford basin (Deep River; Randazzo and others, 1970) show
that the basement is cut by cross faults creating intrabasin grabens
and horsts that, most probably, formed early and concurrently
with the onset of sedimentation (see Sumner, 1977; Cloos and
Pettijohn, 1973). However, field data (e.g., Faill, 1973; Lucas and
^
-J -r
-'
0 I-
I-
-
2-
-
3-
-
NW
Post-Paleozoic activity 329
USGS LINE 9 LONG ISLAND BASIN
S P* 400 500 600
others, 1988) also show that some rift-related deformation of the
onshore basins postdates the youngest rift strata (Early Jurassic)
and may have continued through the Middle Jurassic, when sea-
floor spreading and drifting began offshore. Seismic profiles
across the passive margin show that, except for intrusions by salt
and igneous rocks, the younger drift strata appear essentially
undisturbed (Figs. 8,9).
That the onshore rift basins have been deformed during the
drifting phase is supported by many studies, including McHone
and Puffer (this chapter) and Prowell (this chapter). The defor-
mational continuum and complexity is documented in field stud-
ies of the north-trending Hartford basin, where de Boer and
Clifford (1988) and Wise (1982) show that late Triassic faulting
was accomplished by oblique slip with a dextral shear component
along north-south (grain parallel) fractures in the basement. As
S P# 400 500 600 700
I I I I I I 0
T/UK TERTIARY /QUATERNARY
T/LK
UPPER CRETACEOUS
Figure 8. Seismic-reflection profile and interpreted line drawing of USGS line 9, showing the Long
Island basin beneath the post-rift unconformity. The low-angle western border fault, tilted (sedimen-
tary?) horizons, and high-angle cross faults can be identified on this profile. PRU: post-rift unconformity,
T/UK: top of Upper Cretaceous, T/LK: top of Lower Cretaceous, T/UJ: top of Upper Jurassic. Figures
and caption from Hutchinson and others, 1986.
SE
LOWER CRETACEOUS - I
-
-
CRYSTALLINE
BASEMENT - 2
5 KM
O- -3
-
-