Post-Paleozoic activity - Lamont-Doherty Earth Observatory ...
Post-Paleozoic activity - Lamont-Doherty Earth Observatory ...
Post-Paleozoic activity - Lamont-Doherty Earth Observatory ...
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<strong>Post</strong>-<strong>Paleozoic</strong> <strong>activity</strong><br />
NEWARK BASIN<br />
Figure 6. A. Geologic map of the Newark basin, showing distribution of formations and clusters of<br />
detrital cycles (parallel black lines) in the Passaic Formation (from Olsen, 1980a). Abbreviations of<br />
formations and diabase bodies as follows: B, Boonton Formation; C, Coffman Hill Diabase; Cd,<br />
Cushetunk Mountain Diabase; F, Feltville Formation; H, Hook Mountain Basalt; Jb, Jacksonwald<br />
Basalt; L, Lockatong Formation; 0 , Orange Mountain Basalt; P, Passaic Formation; Pb, Preakness<br />
Basalt; Pd, Palisades Diabase; Pk, Perkasie Member of the Passaic Formation; Rd, Rocky Hill Diabase;<br />
S, Stockton Formation; Sc, carbonate facies of the Stockton Formation; T, Towaco Formation.<br />
B. Structural features of the Newark basin (from Olsen, 1980a). Faults are drawn as normal with dots<br />
on downthrown side; portions of the basin margin not mapped as faults should be regarded as onlaps.<br />
Although all the faults are mapped primarily as normal, some of the major intrabasinal faults are drawn<br />
with strike-slip components. Symbols for the names of structural features are: A, Montgomery-Chester<br />
fault block; B, Bucks-Hunterdon fault block; C, Sourland Mountain fault block; D, Watchung syncline;<br />
E, New Germantown syncline; F, Flemington syncline; G, Sand Brook syncline; H, Jacksonwald<br />
syncline; I, Ramapo fault; J, braided connection between Ramapo and Hopewell faults; K, Flemington<br />
fault; L, Chalfont fault; M, Hopewell fault.<br />
offset in the northern Appalachians and a modified left-stepping<br />
offset in the central and southern Appalachians (Fig. 3; Plate 5A).<br />
They thus appear to be linked to each other by strike-slip faults<br />
that have been identified in other rift basins as transform segments<br />
(Bally, 1981), transfer faults (Gibbs, 1984; Tankard and Welsink,<br />
1988), and accommodation zones (Rosendahl, 1987; Burgess and<br />
others, 1988). Whereas none of the major onshore basins con-<br />
form to a classical graben structure (e.g., the Rhine graben and<br />
the Red Sea), paired basins on the Long Island platform and<br />
those astride the Piedmont gravity high may have had an early<br />
graben history. For these basins, asymmetry may have resulted<br />
from subsequent uplift along the graben axis (as discussed below).<br />
Historically the marginal faults have been modeled as single<br />
planar high-angle faults (Barrell, 1915), as a set of low-angle<br />
planar faults (Ratcliffe and others, 1986), as a series of step faults<br />
(Faill, 1973; Sumner, 1977; Wenk, 1984), and as listric normal<br />
faults (Ratcliffe and Burton, 1985; Hutchinson and others, 1986;<br />
Manspeizer and Cousminer, 1988; Klitgord and others, 1988;<br />
Costain and others, this chapter). The listric normal fault model is<br />
preferred here. Offshore geophysical studies (Hutchinson and<br />
others, 1986; Klitgord and others, 1988; and Hutchinson and<br />
Klitgord, 1988) indicate that these listric faults merge with low-<br />
angle detachment surfaces that have decoupled the upper and<br />
lower crusts beneath the plate margin (Figs. 9, 10, 11).