TECTONICS BLOG Rev. 2021-02-01
Gregory Charles Herman,
PhD
Flemington, New Jersey, USA
Click on an
image to enlarge it
Figure 5. GE map showing the Chesapeake impact crater with respect to a crustal blast pattern, regional structure contours (feet) atop Precambrian basement (Rickard , 1973; Baranoski, 2013), CAMP dolerite dikes (Herman and others, 2015), deep basement faults of the Rome trough (deWitt, 1993), and linear traces of strong aeromagnetic positive anomalies seen in global coverage (Maus and others, 2017). Crustal-compaction values compiled from calcite-strain-gauge work by Engelder (1979), Spang and Groshong (1981), Lomando and Engelder (1984), Craddock and others (1993), and Ong and others (2007). Green circles trace approximate crest lines of lithospheric arches lying circumferentially to the crater at 300 and 760 km radius bracketing circumferential troughs depicted in profile below (figure 6). The Westminster arch of Pennsylvania (Campbell, 1929) defines where pre-impact-age Cenozoic sediment is structurally warped just northward of Chesapeake Bay.
Figure 6. Graphic images captured from an AutoCAD model showing the upper half of sliced Earth detailing profile depths to interior phase boundaries and the hypothetical ITFF strains. Shear fractures locally thicken the lithosphere by compressional wedging downrange of the crater owing to the obliquity of impact. Primary seismic reflections off interior phase boundaries to produce long-wavelength surface ripples cresting at roughly 660 and 2900 km radius from the crater with estimated peak amplitude of 8 km. Profiles a. and b. depict a 20-km diameter sphere descending at an angle of 60o toward Earth’s surface. Profile c. details the geometry of the thickened lithospheric wedge. The wedge is modeled as conforming to seismic p-wave transmission geometry that may vary in depth of penetration with impact angle and size of the bolide (Tectonics Blog Chapter 1). Shear fractures likely develop at acute angle to refractory head waves that dissipate absorbed ground energy within the wedge with the remainder returned to Earth’s surface roughly 2900-km distance from impact. Therefore, compression, excavation, and indentation immediately downrange of the crater corresponds to foreland uplift at great distance from the crater.
Figure 7. Oblique, SW view of the compressed crustal sector and lithospheric wedge that is the foreland part of the radial blast pattern around the Chesapaeake crater. The foreland wedge is portrayed here together with a 5-km diameter bolide descending along a moderate angle from south to north. The primary path of crustal compression coincides with the azimuth of Chesapeake Bay and the maximim measured value of crustal compaction (%) in the foreland based on mechanically twinnned calcite (see refs in fig. 5). The compression axis bisects the Juniata Culmination and a foreland wedge of thickned crust through parts of the New York recess and Pennsylvania Salient. Also shown are locations of the Re-Os isotope data (Mathur and others, 2015), the Tom’s River impact, and Eocene magmatism. Nickelsen’s Bear Valley (1987) and Cove Valley (1996) structural studies of deformation kinematics straddle the culmination. C – compression, M – marginal, and E – extensional crustal sectors surrounding the crater (white circular lines).
Figure
8
Photographs of complex transtentional structures of probable Mesozoic
age with later (Cenozoic?) wrenching in upper Paleozoic strata at a coal
mine from Bear Valley, Pa. (Nickelsen, 1963; location noted in fig. 1).
Late-stage structural grabens (A) of probable Newark group (fig. 2;
Herman, 2009) dip steeply west and have two sets of slickenlines (B) on
graben-bounding faults. The earlier slickenlines indicate normal,
dip-slip shearing during graben development, and later ones indicate
compressional wrenching that is congruent to regional joints sets of
sub-parallel strike (Engelder and others, 2001). Photo A from
www.princeton.edu.
Figure
9.
Optical BTV imagery collected in Early Mesozoic bedrock in New Jersey
reveal late-stage, ~E-W-striking, reverse shear fractures that dip
gently SE (circled), less so to the NW, that are among the most open and
permeable conduits in these fractured aquifers. The schematic diagrams
on the left illustrates a gently dipping plane cut by a borehole in
wrapped and unwrapped versions of an optical-borehole image. The
interpretation is conducted on the unwrapped image. Note how early,
mineralized
fractures of steeper dip are sheared
and offset in the image to the right along one of the moderately dipping
reverse shear planes. Well locations and details from Herman (2015).
Depth units for the BTV imagery are feet below land surface.
Figure
10.
Mesozoic Bedrock in the Trenton, NJ is structurally inverted by reverse
shear fractures and faults striking about E-W that overprint and
reactivate earlier tensile-transitional fractures and faults developed
from Newark rifting (Herman, 2009). The complex structural geometry in
the region results in positive, transpressional flower structures that
are deeply weathered and commonly masked at land surface.
Note the location of core MW-20C at
RACER-TRENTON where transtentional fault breccia healed with spar
calcite are overprinted and twinned by tectonic compression (fig. 11).
Figure 11. Calcite-cemented autoclastic breccia in the Stockton Formation retrieved at MW-20C by Haley-Aldrich, Inc. at he RACER-TRENTON site (fig. 10 and Herman, 2016). Figure 12. GE display of the mid-Atlantic , continental and oceanic margin of the North American Plate (NAP), centered near 40o latitude and -75o longitude showing recent crustal motions determined using ground-fixed GPS receiving stations, crustal seismic zones, principal axes of crustal compression reported from focal-mechanism solutions from well-constrained earthquakes, and some key structural analyses used for interpretations (Herman, 2016). Note the parabolic line connecting the seismic zones wrapping around the rising Adirondack Mountains, which appear to act as a buttress in resisting the slow, northwestward plate drift with rates that slowly increase NE up the spine of the Appalachian Mountains. Also note the pronounced GPS-velocity break on the western side of the Pennsylvania Salient.
Figure 14. A structural palinspastic reconstruction of the Pennsylvania Salient was an unpublished aspect of my Masters thesis at the University of Connecticut (Herman, 1984) that was included in Hatcher and others (1989) showing that the curved mountain chain fans outward from the head of Chesapeake Bay. |
Chapter 2.
Mid-Cenozoic
tectonic disruption of the
Central Appalachians by the Chesapeake Invader
Introduction * Geological evidence * Discussion * References * Impacttectonics.org
Abstract
Geological, geochronological, and geophysical data mapped across the Pennsylvania Salient and New York Recess show that this region was uplifted from tectonic compression in the Cenozoic period. One phase of regional lithospheric compression is proposed here to have occurred in the Tertiary period stemming from the oblique bolide impact that produced the large crater now buried beneath the mouth of Chesapeake Bay, Maryland, USA (Poag and others, 1992; 1994, Koerbel and others, 1996; Poag, 1996; 1997, and 1999; Horton and others, 2005). The hypervelocity impactor is modeled to have obliquely struck the Chesapeake Bay area along a decent trajectory aligned along the bay axis (azimuth 347o). The impact compressed and thickened the Appalachian crust in a foreland sector situated downrange where brittle shear fracturing and faulting was focused as part of a circumferential blast pattern and far-reaching lithospheric welts formed at great distances from the crater. The foreland compressional sector fans northward away and outward from the impact crater into the central Appalachian foreland where bedrock strains of Cenozoic age affect all older rocks and measurements of bulk crustal compaction may reach 10%. Prior to the recent discovery of the concealed crater, most of the tectonic effects interpreted in this region are thought to solely result from the suturing of tectonic plates during Paleozoic orogenesis. In contrast, it is shown how this bolide impact contributed to the geological expression of the central Appalachian Mountains by overprinting the Paleozoic orogenic belt, a transtentional strain field imparted by Mesozoic continental rifting, and basal Tertiary strata of the Cenozoic coastal plain. The Chesapeake impact is therefore one of the latest of a series of causative tectonic agents contributing to the physiographic expression of the scalloped, passive margin.
The cratering effects from large, hypervelocity asteroid, comet and meteorite (bolide) impacts on terrestrial planet and moon surfaces are visually apparent and well known. Numerous studies have shown that large, episodic bolide collisions with host bodies disrupt the atmosphere, obliterate the impactor, and leave telltale scars behind on the host’s crust including not only complex craters, but near-field fracture fields lying close to the point of impact (Sharpton and Ward, 1990; Koerbel and Henkel, 2005). But there has been little consideration for, or accounting of impact-tectonic, far-field (ITFF) crustal strains stemming from large-bolide impacts lying outboard of the crater at distances of hundreds to thousands of kilometers (Chapter 1). Moreover, there are only abstract concepts of any long-lasting geodynamic consequences to periodic, large-bolide impacts (Herman, 2006).
Evidence for a massive,
catastrophic disruption of this region's crust and lithosphere is summarized
herein that includes post-Mesozoic brittle strains found throughout the central
Appalachians stemming from dissipated ground strains imparted by the Chesapeake
impact event. Poag (1999) named the asteroid that struck the Mid-Atlantic margin
of the North American tectonic plate (NAP) during the late Eocene epoch (35.5
Ma) 'The Chesapeake Invader'. The resulting Chesapeake impact crater is about
85-kilometer diameter with circumferential, outboard gravity anomalies ringing
the structure with radii exceeding 150 km (fig. 1). It was discovered lying
beneath a blanket of Cenozoic sediment shed off the flanking Appalachian
Mountains and is correlated here to regional, penetrative lithospheric and
crustal strain fields including circumferential low-amplitude lithospheric welts
situated hundreds to thousands of kilometers distance away from the crater
(figures 1, 3, 5, 6 and Chapter
1).
Potential-field geophysical
data and structural-kinematics mapped in Paleozoic and Mesozoic bedrock in Pennsylvania
and New Jersey, together with radiometric age dates of mineralized faults (Mathur and others,
2008; 2015) signal the far-field, Cenozoic-aged tectonic disruption of
the central Appalachians. ITFF strains stemming from
this impact also include structurally compressed, thickened and elevated
crust downrange of the crater indicating an oblique descent trajectory along the
bay axis of azimuth 347o (fig.
1). The bedrock structural kinematics are
consistent with a Cenozoic-age tectonic northwest-directed push from the head of
Chesapeake Bay that tightened the central Appalachian foreland fold-and-thrust
belt, accentuated the scalloped Appalachian margin, and left Cenozoic igneous
intrusions systematically aligned in its wake (figs. 3 and 5). These tectonic
aspects overprint strain fields stemming from earlier Paleozoic orogenesis and
Mesozoic rifting, the latter also having localized epeirogenic movements
(Herman, 2015) associated with intrusive emplacement of the Central Atlantic
Magmatic Province (CAMP) into the crust during breakup of Pangaea (Marzolli and
others, 1999; Herman and others, 2013).
Stratigraphic, structural, geophysical, and radiometric evidence
The regional
stratigraphic succession, structural observations, and geophysical evidence
leading to this ITFF strain hypotheses are detailed
below. Figure 2
summarizes the tectono- stratigraphic groups for the New Jersey area in the
central Appalachians covering Proterozoic through Cenozoic crustal rocks
(Herman, 2015).
An expanded Cenozoic section includes subunits
separated by major unconformities developed on the central Appalachian margin of
the North American tectonic plate (NAP) beginning with a prominent one at the
Cretaceous-Tertiary boundary that corresponds with the timing of Chicxulub
impact event.
Figures 1 and 4 summarize radiometric ages obtained from
outcropping or cored sulfide-mineralized fault breccia retrieved from both Paleozoic and
Mesozoic bedrock that plot near an isochron of ~35 Ma (figure 1 and Mathur and
others, 2015). This geochronology was obtained from sulfide-mineralized
fault breccia having Os isotopic concentrations indicating upper-mantle to lower
crustal depths of origin (Mathur and others, 2008). Early sulfide
mineralization is also seen in extension veins of Mesozoic age like those
commonly associated with calcite vein fill and hydrocarbon expulsion from the
Newark rift basins (Parnell and Monson, 1995; Herman, 2009). Early veins in
foreland carbonate and siliciclastic rocks also have sulfides with calcite and
quartz intergrowths respectively that may stem from older Alleghanian
orogenesis, but the earliest forms and varieties of vein sulfides including
pyrite (with lesser chalco- and arsenopyrite) are superseded by sulfide-cemented
fault breccia (Mathur, 2008) returning a 29-point isochron and indicating Eocene
ages that closely match the impact age when considering measurement errors
(table 1 and figure 4). Earlier vein sulfides do not return reliable Re-Os
isochron because Re may not have reached closure temperature in pyrite (~300o
C; Brennan and others, 2000) during either the Mesozoic thermal pulse or any
Mississippi-valley type, late-Paleozoic sulfide mineralization (Roden and
Miller, 1989; Kohn and others, 1993; Blackmer and others, 1994; Smith and Faill,
1994; Smith, 2003). Fluid-inclusion analysis of sphalerite mineralization in
Mesozoic rocks provides age estimates of a possible 155-167 Ma (Cretaceous)
hydrothermal event in this region (Smith, 2003), however fluid inclusion
temperatures from the Eocene fault breccia indicate a higher-temperature thermal
event that exceeded 300o
C (Mathur and others, 2008). This Re-Os isotopic data clearly reflect an
impact-driven epigenetic mineralization event in the central Appalachians having
a deep lithospheric origin.
Outcrop-based finite-strain
studies of Paleozoic rocks of the Appalachian Plateau through Mesozoic-aged
bedrock of the Newark Supergroup also show, penetrative bulk compaction of
rock-cementing calcite grains approaching 10% within in a finite-strain field
fanning northward out in front of Chesapeake Bay (figs 3 and 5). Bedrock in this
region was subject to secondary crustal compaction that overprints both
Alleghanian orogenic and Newark rift structures. The Tertiary disruption would
likely have been a sudden push that translated and thickened the crust as part
of a lithospheric wedge downrange of the crater. We portray the event in Google Earth
(figs. 3 and 7) using an impactor of 10-km radius and a 45o incidence
angle to
give this tectonic event geospatial perspective (see
also Chapter 1). Most reports of the Chesapeake
Invader cite a 3-5 km bolide based on the crater dimensions but this
multi-ringed impact structure was probably more energetic than prior estimates.
Circumferential, positive Bouger gravity anomalies
clearly lie at 150-km radius from the point of impact (fig. 1), and although the
oblique incidence angle is poorly constrained, it may become
more clear after a thorough compilation and review of other post-impact tectonic
structures mapped in the central and southern Appalachians that must fall into
the other, marginal and extensional strain sectors arranged circumferentially
about the crater (figs. 3 and 5).
The regional stratigraphic
succession and structural kinematics of Paleozoic rocks throughout the
Pennsylvania Salient and New York Recess (fig. 2) indicate at least two episodes
of post-CAMP tectonic inversion in the region (Herman, 2015; Merguerian, 2015).
The earliest hypothetically stems from the Mesozoic-ending Chicxulub impact in
the Gulf of Mexico (~65 mya) and is overprinted by a later event having
cross-cutting kinematic indicators in the Pennsylvania Valley & Ridge Province
showing sinistral-oblique slip slip congruent with a NNW-directed tectonic push
directed up Chesapeake Bay. The resultant structures fan outward downrange of
the crater into the Appalachian foreland (figs. 1, 3, 5, 7 and 8).
Mesozoic (Newark) transtentional structures
affecting CAMP rocks are also reactivated and structurally inverted by this late
compression that opened suitably oriented fractures (fig. 9) and imparted
mechanical twins in calcite cemented tensile-transitional fractures mapped as
joints and autoclastic fault breccia in Triassic rocks (figs.
10 and 11).
Steckler and others (1993) estimate a minimum of 3 km
of denudation over the Newark basin and surrounding region based on
fission-track analysis of zircons from both Proterozoic basement and Jurassic
basalts. More
recent estimates of up to 6 km of erosion in the piedmont are reportedly
associated with late-stage intra-basin faulting (Withjack and others, 2013).
Basal sections of the NJ Coastal Plain of Mesozoic
age younger than the impact are likewise compressed, fractured, and locally
folded (Herman and others, 2013; Herman, 2015; 2016). It is likely that this
crustal disturbance also produced a pronounced, post-impact, mid-Tertiary
unconformity in the region (fig.
2).
Miocene and younger strata mostly lack any
secondary tectonic structures except in areas in the Delaware coastal plain
(Andres and Howard, 1998) in an area having some of the fastest rates of crustal
subsidence (~3-4 mm/yr) based on ground-fixed GPS monitoring and reporting
(Herman, 2016). The relatively rapid rate of current subsidence in the
Pennsylvania culmination may reflect an inherited tectonic response to the Early
Tertiary uplift (fig. 12). The pronounced, linear break in the historical GPS
vertical-velocity field on the west side of the Pennsylvania salient (fig. 12)
therefore probably signals current, continued and prolonged far-field
crustal-strains that continue to operate today as inherited from this ancient
event.
The late-stage penetrative
tectonic compaction and wrenching reported in the Appalachian is modeled here as
an fanned-shaped envelope whose basal geometry follows P-wave refraction paths
that penetrate most deeply directly in front of the oblique impact, and diminish
in intensity laterally (figs. 6 and 7). We hypothesize the return of a
considerable amount of impact-generated ground energy at radial distance of
about 2900 km from the crater, the same approximate radial distance to the
core-mantle boundary, and therefore perhaps, a significant distance away from
the crater where epeirogenic welting is pronounced as a result of constructively
interfering far-field lithospheric strain responses, one of shear fracturing and
rippling of Earth’s crust at distances reflective of internal mineral-phase
boundaries.
Syntheses of late Cenozoic geological evolution of the middle Atlantic passive margin are provided by Poag and Sevon (1989) and Pazzaglia and others (2006). They report a deeply eroded early Tertiary Appalachian landscape of lower relief than today. Climate change, epeirogenic uplift, or rapid increase in the size of the Atlantic slope drainage basin, or some combination of all three factors, initiated the stripping of mature regolith in the middle Miocene and delivery to the Fall Zone. Increased sediment flux into the Baltimore Canyon trough (BCT), coupled with erosional unloading caused flexure of the margin with the Fall Zone located at the flexural hinge (Pazzaglia and Gardner, 2004). Continued Middle Tertiary flexural warping of the margin arched early Miocene terraces and contributes to the continued incision by the Susquehanna River channel. The incised Appalachian landscape now delivers an immature, heterolithic load to the Coastal Plain and shelf region that reflect both periodic, positive and negative, isostatic adjustment to the loading and removal of Quaternary continental glaciers and slow continental convergence on a passive margin. Erosion rates in Susquehanna River basin reportedly doubled from prior amounts immediately after the Chesapeake impact at ~ 35.5 Ma based on cosmogenic dating of the oldest river terraces and associated upland gravel at 36.1 + 7.3 Ma (Pazzaglia and others, 2006). Younger terraces yield dates of 19.8 +2.7 Ma and 14.4 +2.7 ka respectively. Campbell (1929) mapped the oldest gravels as mantling a doubly-plunging basement arch referred to as the Westchester anticline lying immediately foreland of Chesapeake Bay (fig. 5).
The inclusion of far-field,
impact generated strains as part of the tectonic expression of the Appalachian
Mountains addresses many, puzzling aspects of central Appalachia. For example,
Herman (1984; 1985) reported complex tectonic structures in the Pennsylvania
culmination that don’t fit the model foreland fold-and-thrust belt paradigm
following a ‘break-forward’ advance of stacked thrust sheets during orogenesis.
Paleozoic beds are structurally tightened and elevated in the Juniata
Culmination relative to flanking areas (fig. 3), and the manner in which the
Pennsylvania crust was crumpled and compounded from thrust faulting is
uncharacteristic and contains ‘out of sequence’ sections where beds subsequently
pushed and raised along very steep reverse faults.
Another noteworthy aspect of this work are
conjugate planar microfractures (PMs) seen in strained Silurian quartzite
occupying fold limbs across the width of the Pennsylvania culmination (fig. 14).
These rocks are the basal section of the blind-thrusted ‘roof’ section that was
under thrusted and mostly compacted by wedge faulting and folding during
penetrative cleavage development in the associated finer-grained clastic and
carbonate strata. The PMs in the Tuscarora resemble planar deformation features
(PDFs) in quartz grains subject to shock metamorphism at pressures of ~10 to 30
Gpa (French, 1998; Lee and Leroux, 2015) but occur with less density (fig. 7).
Because
PDFs are shock barometers, more work is needed in order to understand if any of
the conjugate PMs in the Juniata culmination result from tectonic orogeny, shock
geodynamics, or both. Nevertheless, the out-of-sequence, tightened fault slices
in the Juniata part of culmination (Herman, 1984; Sak and others, 2014) are
sympathetic with other late-stage brittle shear strains reported at Cove Valley
and Bear Valley (Nickelsen, 1987; 1996), where late wrench faulting on steep
faults that are congruent with a late, N-S push centered directed from the head
of Chesapeake Bay (fig. 5).
In the early 1980s when the
Appalachian
Tectonics Study Group were interpreting
root causes of salient curvature and crustal strains stemming from orogenesis,
there was no knowledge of the Chesapeake impact crater, or for that matter,
actual plate motions in the region that are now available from global
positioning systems (Herman, 2015). Early attempts to reconcile curvature of
secondary geological structures in the Pennsylvania Salient were only considered
with respect to Alleghanian orogenesis and contradicted the simplest
reconstruction of serial palinspastic sections that merged to a point at the
head of Chesapeake Bay (Geiser, 1988; Hatcher and others, 1989). Attempts at
deciphering the kinematic evolution of the Pennsylvania Salient using remnant
thermal magnetization of beds involved in regional folding have proven uncertain
(Cederquist and other, 2006).
However, the aforementioned Re-Os radiometric
evidence of widely distributed Lower Tertiary, brittle faulting associated with
late-stage compaction in the Pennsylvania Salient and New York Recess
substantiates the widespread, regional, far-field brittle strain field fanning
outward in front the Chesapeake Bay impact crater for distances greater than 500
km through into foreland areas (Mathur and others, 2015; Herman 2015).
Because such penetrative
structures probably stem from the Chesapeake impact, then consideration should
be extended to large impacts elsewhere and associated
far-field strains that probably include the
concentric lithospheric welts lying outboard of the crater at hundred to
thousands of kilometers distances. In particular, the well-known Chicxulub
crater appears to have similar far-field welts
at
~660, ~1500, and ~2900 radii that are reflective of depths to major phase
boundaries in Earth’s interior (Herman, 2006) and represent the radial
dispersion of ground energy following
impact.
This helps explain cratonic epeirogenic
movements and not only illustrates the likelihood of far-field strain effects
occurring on Earth, but also points to the need for plate-tectonic theory to
include such far-field impact-generated strains on other terrestrial planets.
The introduction of periodic catastrophism into modern plate-tectonic theory
would include such far-field lithospheric strains and any geodynamic fluxes,
plate fragmentation episodes or adjustments caused by large, hypervelocity
bolide impacts on terrestrial planets.
Historical interpretations of
tectonic plate motions also lend credence to these impact-tectonic hypotheses.
For example, at the dawn of the Cenozoic, shortly after the Chicxulub impact in
the Gulf of Mexico, major plate reorganizations began that involved the North
American, Eurasian, and African plates accompanied by major changes in the
deep-ocean water circulation, permitting cold polar waters to move southward in
the Atlantic Ocean basin (Klitgord and Schouten, 1986).
Now, the North American tectonic plate and
border plates in the Central American region move in concert about a hub
containing the Chicxulub impact crater on the south rim of the Gulf of Mexico
(Herman, 2005). Moreover, shortly after the Chesapeake impact oceanic sea-floor
spreading halted west of Greenland and suddenly accelerated to the east by
Iceland where it’s currently focused in the North Atlantic region (Dore´ and
others, 2015). Such corroborative evidence focuses consideration on how these
two, known, large-bolide impacts on the NAP, at the beginning of and during the
Cenozoic Era, have not only helped shape the crust, but continue to exert a
dynamic neotectonic signature on our landscape that is so remarkably
remote
to the causative agents.
Ribiero
(2002) postulated the need for considerations of external forces on our open,
dynamic tectonic system, and finally over the past two decades we have
ground-fixed, GPS instrumentation available to gauge actual plate motions to
gain a realistic perspective on plate dynamics.
A plate-tectonic paradigm
that includes far-field strain effects stemming directly from periodic and
catastrophic bombardment by large bolides including intraplate crustal
deformation and epeirogenesis simply makes sense. For now though, more work is
needed to hypothesize and test models that integrate short- and long-term strain
mechanisms that serve to dissipate pin-point energy fluxes, and the geometry of
associated crustal and lithospheric strain fields. By definition, neotectonic
strains are those that form in our current stress regime (Stewart and Hancock,
1994). In this context, do catastrophic impact strains qualify as a neotectonic
features, or is that reserved to the more standard, uniformitarian viewpoints
only? Regretfully, this work leaves many aspects of this neotectonic treatment
and some conclusions unaddressed. For example, the scalloped, curved nature of
our continental interior has been historically chronicled and debated for
decades (Thomas, 1977; Marshak, 2004; Wise and Werner, 2004).
The along-strike transition from the
Pennsylvania salient in to the New York recess is perhaps the most studied and
reported instance of a scalloped, passive margin that has historically been
treated mostly as a byproduct of differential plate convergence with irregular
docking of land masses at different places, times and directions as the orogenic
suture closed.
The evidence presented here supports the
rather unheralded notion that much of our regional architecture, and especially
the geometry of our scalloped margin, is more likely a product of continental
rifting (Herman, 2014; 2015).
This work uses modern
geospatial tools to help outline some new hypotheses to test both new and old
ideas. We are encouraged by recent technological advances available with
geographic information systems that facilitate the dynamic study and portrayal
of Earth systems. Although considered tectonically passive with respect to
currently active orogenic margins, the central Appalachian region has been
steadily drifting as part of the NAP but punctuated with sudden tectonic
upheavals that humanity has been fortunate to evade simply by our juvenile
presence here.
These conditions echo observations by Gould
(2007) who characterized biological punctuated equilibrium through geologic
time, which leads us to think that large, catastrophic impacts are causative
agents for concurrent geological and biological revolutions on this terrestrial
planet occupying the Goldilocks zone.
Alexander, S. S., Cakir, R., Doden, A. G., and others, compilers, 2005, Basement depth and related geospatial database for Pennsylvania: Pennsylvania Geological Survey, 4th ser., Open-File Report OFGG 05-01.0, 1 map, scale 1:500,000.
Andres, S.
A. and Howard, S.
C., 1998, Analysis of deformation features at the Pollack Farm site, Delaware,
in Benson, R. N., ed., Pollack Farm Fossil
site, Delaware: Delaware Geological Survey Special Publication No. 21, p. 47-54.
Baranoski, M.T.,
2013, Structure contour map on the Precambrian unconformity surface in Ohio and
related basement features (ver. 2.0): Columbus, Ohio Department of Natural
Resources, Division of Geological Survey Map PG-23, scale 1:500,000, 17 p. text.
Blackmer, G. C., Omar, G. I., and Gold, D. P., 1994, Post-Alleghanian unroofing history of the Appalachian Basin, Pennsylvania, from apatite fission track analysis and thermal models: Tectonics, v. 13., p. 1259-1276.
Brennan, J.M.,
Cheriak, D. J., Rose, L.A. (2000) Diffusion of Os in pyrrhotite and pyrite:
implications for closure of the Re-Os isotopic
system, Earth and Planetary Science , v. 180 399-413
Brenner, G. J., 1963, The spores and pollen of the
Potomac Group of Maryland: Maryland Department of Geology, Mines, and Water
Resources Bulletin 27, 215 p.
Campbell, M. R.,
1929, Late deformation of the Appalachian piedmont as determined by river
gravels: National Academy of Sciences Proceedings: v. 15, no. 2, p. 156-161.
Cederquist, D. P.,
Van der Voo, R., and van der Pluijm, B. A., 2006, Syn-folding demagnetization of
Cambro-Ordovician carbonates from the Pennsylvania Salient post-dates oroclinal
rotation: Tectonophysics, v. 422, p. 41-54.
Craddock, J. P.,
Princen, M., Wartman, J, Xia, H., and Liu., J., 2016, Calcite Twinning in the
Ordovician Martinsburg Formation, Delaware Water Gap, New Jersey, USA:
Implications for Cleavage Formation and Tectonic Shortening in the Appalachian
Piedmont Province: Geosciences v. 6(1), No. 10; p. 1-19.
deWitt, W., Jr.,
1993, Principal Oil and Gas Plays in the Appalachian Basin,( Province 131): U.S
Geological Survey Bulletin 1839-I. P. i1-i37.
Dore´, A. G.,
Lundin, E. R., Kusznir, N. J., and Pascal, C., 2015, Potential mechanisms for
the genesis of Cenozoic domal structures on the NE Atlantic margin: pros, cons
and some new ideas, in, Johnson, H., Dore´, A. G., Gatliff, R. W., Holdsworth,
R., Lundin, E. R., and Ritchie, E, J. D. , eds., The Nature and Origin of
Compression in Passive Margins: Geological Society, London, Special
Publications, v. 306, p. 1–26.
Earth Impact
Database, 2015: Plantary and Space Science Centre, University of New Brunswick,
Canada, www.passc.net/EartthImpactDatabase/
Engelder, T.,
1979, The nature of deformation within the outer limits of the central
Appalachian foreland fold and thrust belt in New York State, Tectonophysics, 55,
289-310.
Engelder, T.,
Haith, B.F., and Younes, A., 2001, Horizontal slip along Alleghanian joints of
the Appalachian plateau: evidence showing that mild penetrative strain does
little to change the pristine appearance of early joints: Tectonophysics, v.
336, p. 31-41.
Ettensohn, F. R., 2008, The Appalachian foreland
basin in Eastern united States,
in, Miall, A.
D., ed., The Sedimentary Basins of the United States and Canada, Chapter 4,vol.
5:Sedimentary Basins of the World, Elsevier, The Netherlands: 2008, pp. 105 –
179.
French, B. M., 1998,
Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial
Meteorite Impact Structures (PDF).
Lunar and Planetary Institute
Contribution No. 954. Houston,
Texas, p. 120.
Fullagar, P.D.,
and Bottino, M.L., 1969, Tertiary felsite intrusions in the Valley and Ridge
province, Virginia: Geological Society of America Bulletin, v. 80, no. 9, p.
1853–1858.
Geiser, P. A.,
1988, The role of kinematics in the construction and analysis of geologic cross
sections in deformed terranes: Geological Society of America Special Paper 222,
p. 47-76.
Gould, S. J., 2007, Punctuated Equilibrium:
Belknap Press of Harvard University Press, Cambridge, Mass., 408 p.
Hatcher, R. D.,
Jr., 2008, Tracking lower-to-mid-to-upper crustal deformation processes through
time and space through three Paleozoic orogenies in the southern Appalachians
using dated metamorphic assemblages and faults: Geological Society of America
Abstracts with Programs, Vol. 40, No. 6, p. 513.
Hatcher, R. D., Jr., Thomas, W. A., Geiser, P. A.,
Snoke, A. W., Mosher, S., and Wiltschko, D. V., 1989,
in
Hatcher, R. D., Jr., Thomas, W. A., and Viele, G. W., eds., The
Appalachian-Ouachita Orogen in the United States: Boulder, Colorado, Geological
Society of America, The Geology of North America, v. F-2. P. 233-318.
Herman, G. C., 2016, Borehole Televiewer Synoptic and
Hydrogeologic Framework of Adjacent RACER and NAWC Industrial Sites, West
Trenton, Mercer County, New Jersey, in Shallow
subsurface geophysical investigations in environmental geology, Gagliano, M. P.
and Macaoay Ferguson, S., eds., 33rd Annual proceedings and field guide of the
Geological Association of New Jersey, Trenton, NJ, p. 66-99.
Herman, G. C., 2015, Neotectonics of the New York Recess, in Herman, G. C., and Macaoay Ferguson, S., Neotectonics of the New York Recess: 32nd Annual proceedings and field guide of the Geological Association of New Jersey, Lafayette College, Easton, Pa., p. 80-151
Herman, G. C., Dooley, J. H., and Monteverde, D. H., 2013, Structure of the CAMP
bodies and positive Bouger gravity anomalies of the New York Recess,
in
Benimoff, A. I., ed., Igneous processes during the assembly and breakup of
Pangaea: Northern New Jersey and New York City: 30th Annual Meeting of the
Geological Association of New Jersey, College of Staten Island, N.Y., p.
103-142.
Herman, G. C., 2009, Steeply-dipping extension fractures in the Newark basin (5
MB PDF), Journal of Structural Geology, V. 31, p. 996-1011.
Herman, G. C., 2006, Neotectonic setting of the North American Plate in relation
to the Chicxulub impact: Geological Society America Abstracts with Programs,
Vol. 38, No. 7, p. 415, 1.3 MB PDF
Herman, G.C.,
1984, A structural analysis of a portion of the Valley and Ridge Province of
Pennsylvania [M.S. thesis]: Storrs, University of Connecticut, 107 p.
Herman G. C., and Geiser, P. A., 1985, A "passive roof duplex" solution for the
Juniata Culmination, Central Pennsylvania: Geological Society America Abstracts
with Programs, v. 17, no. 1, p. 24.
Horton, J.W., Jr., and Izett, G.A., 2005,
Crystalline-rock ejecta and shocked minerals of the Chesapeake Bay impact
structure, USGS-NASA Langley core, Hampton, Virginia, with supplemental
constraints on the age of impact, chap. E in
Horton, J. W., Jr., Powars, D. S., and Gohn,
G. S., eds., Studies of the Chesapeake Bay impact structure -The USGS-NASA
Langley corehole, Hampton, Virginia, and related coreholes and geophysical
surveys: U.S. Geological Survey Professional Paper 1688, p. E1-E30.
Horton, J.W., Jr., Powars, D.S., and Gohn, G.S., eds., 2005, Studies of the
Chesapeake Bay impact structure—The USGS-NASA Langley corehole, Hampton,
Virginia, and related coreholes and geophysical surveys: U.S. Geological Survey
Professional Paper 1688-A-K, separately paginated, 453 p., 2 oversize figures.
Howe, S. S., 1981, Mineralogy, fluid inclusions, and stable isotopes of
lead-zinc occurrences in central Pennsylvania: unpublished M.S. thesis, The
Pennsylvania State University, 155 p.
Klitgord, K. D., and Schouten, H., 1986, Plate kinematics of the central
Atlantic; in Vogt, P. R., and Tucholke, B. E., eds., The Geology of North
America, Volume M., The Western North Atlantic Region: Geological Society of
America.
Koeberl, C. and
Henkel, H. (Eds.), 2005, Impact Tectonics: Springer.com, v. XIX, 552 p.
Kohn BP,
Wagner ME, Lutz TM, Organist G (1993) Anomalous Mesozoic thermal regime, central
Appalachian Piedmont: evidence from sphene and zircon fission-track dating:
Journal of Geology, v. 101, p. 779–794
Komitz, M. A., and
Pekar, S. F., 2001, Oligocene eustasy from two-dimensional sequence
stratigraphic backstripping: Geological Society of America Bulletin, vol. 113,
no. 3, p. 291- 304.
Koeberl, C.,
Poag, C.W., Reimold, W.U., and Brandt, D., 1996, Impact
origin of the Chesapeake Bay structure and the source of the North American
tektites: Science, v. 271, p. 1263-1266.
Lee, M. R., and
Leroux, H., 2015, Planetary minerology: The mineralogical society of Great
Britain and Ireland, 314 p.
Lomando, A. J. and
Engelder, T., 1984, Strain indicated by calcite twinning: Implications for
deformation of the Early Mesozoic Northern Newark Basin, New York: Northeastern
Geology, vol. 6, no. 4, p. 192-195.
Lucas, M., Hall, J., and Manspeizer, W., 1988, A
foreland-type fold and related structures in the Newark rift basin,
in
Manspeizer, W., ed., Triassic-Jurassic rifting, continental breakup and the
origin of the Atlantic Ocean and passive margin: Elsevier, Amsterdam, p.
307-332.
Marzoli, A.,
Renne, P., Piccirillo, E., Ernesto, M., Bellieni, G., and De Min, A, 1999.
Extensive 200-million-yearold continental flood basalts of the Central Atlantic
Magmatic Province: Science, v. 284, p. 616–618.
Mathur, R. D.,
Mutti, L., Barra, F., Gold, D., Smith, R. C., Doden, A., Detrie, T., Mc
Williams, A. , 2008, Fluid inclusion and Re-Os isotopic evidence for hot,
Cenozoic mineralization in the central Pennsylvanian Valley and Ridge Province:
Mineralogy and Petrology, v. 93, p. 309-324.
Mathur, R., Gold, D. P., Ellsworth, C. J., Doden, A. G., Wilson, M., Ruiz, J.,
Scheets, B. E., and Herman, G. C., 2015, Re-Os isotope evidence of Early
Tertiary crustal faulting and sulfide-mineralization in Pennsylvania with
probable ties to the Chesapeake Bay bolide impact in Maryland, USA,
in
Herman, G. C., and Macaoay Ferguson, S., eds., Neotectonics of the New York
Recess: 32nd Annual proceedings and field guide of the Geological Association of
New Jersey, Lafayette College, Easton, Pa., p. 68-79.
Maus, S., Barckhausen, U., Berkenbosch, H., Bournas, N., Brozena, J.,
Childers, V., Dostaler, F., Fairhead, J.D., Finn, C., von Frese, R.R.B., Gaina,
C., Golynsky, S., Kucks, R., Lühr, H., Milligan, P., Mogren, S., Müller, D.,
Olesen, O., Pilkington, M., Saltus, R., Schreckenberger, B., Thébault, E., and
Caratori Tontini, F., 2017, EMAG2: A 2-arc-minute resolution Earth Magnetic
Anomaly Grid compiled from satellite, airborne and marine magnetic measurements:
http://geomag.org/info/Smaus/Doc/emag2.pdf
Miller, K.G., Browning, J.V., Mountain, G.S., Sheridan, R.E., Sugarman, P.J.,
Glenn, S., and Christensen, B.A., 2014, History of continental shelf and slope
sedimentation on the US Atlantic margin: Geological Society of London Memoirs,
v. 41, p. 21-34.
Miller, K.G., 2015, Keynote abstract. The New JErey coastal plain: A key to
deciphering past, present, and future sea-level change,
in
Herman, G. C., and Macaoay Ferguson, S., Neotectonics of the New York Recess:
32nd Annual proceedings and field guide of the Geological Association of New
Jersey, Lafayette College, Easton, Pa., p. 154-157.
Merguerian, C., 2015, Review of New York City bedrock with a focus on brittle
structures,
in
Herman, G.C., and Macaoay Ferguson, S., eds., Neotectonics of the New York
Recess: 32nd Annual proceedings and field guide of the Geological Association of
New Jersey, Lafayette College, Easton, Pa., p. 17-67.
Nickelsen, R.P.,
1963, Fold patterns and continuous deformation mechanisms of the central
Pennsylvania folded Appalachians, in Cate., A., ed., Guidebook: Tectonics and
Cambro-Ordovician stratigraphy, central Appalachians of Pennsylvania: Pittsburgh
Geological Society with the Appalachian Geological Society, Pittsburgh, Pa., p.
13-29.
Nickelsen, R.P., 1987, Sequence of structural stages of the Alleghany orogeny at the Bear Valley Strip Mine, Shamokin, Pennsylvania: Geological Society of America Centennial Field Guide—Northeastern Section
Ong, P.F. van der
Pluijm, B.A., Van der Voo, R., 2007, Early rotation and late folding in the
Pennsylvania salient (U.S. Appalachians): Evidence from calcite-twinning
analysis of Paleozoic carbonates: Geological Society of America Bulletin (2007),
119(7-8), p. 796-804.
Parnell, J., and
Monson, B., 1995, Paragenesis of hydrocarbon, metalliferous and other fluids in
Newark Group basins, Eastern U.S.A., Institute of Mining and Metallurgy,
Transactions, Section B: Applied Earth Science; v. 104, p. 136-144.
Pazzaglia, F.J.,
and Gardner, T.W., 1994, Late Cenozoic flexural deformation of the middle U.S.
Atlantic passive margin: Journal of Geophysical Research, vol. 99, no. B6, 12,
p. 143-157.
Pazzaglia, F.J., and 8 others, 2006, Rivers,
glaciers, landscape evolution, and active tectonics of the central Appalachians,
Pennsylvania and Maryland,
in Pazzaglia,
F. J., ed., Excursions in Geology and history: Field trips in the Middle
Atlantic States: Geological Society of America Field Guide 8, p. 169-197.
Poag, C.W.,
1996, Structural
outer rim of Chesapeake Bay impact crater: Seismic and bore hole evidence:
Meteoritics and Planetary Science, v. 31, p. 218-226
Poag, C.W.,
1997, Chesapeake
Bay bolide impact: A convulsive event in Atlantic Coastal Plain evolution,
in
Segall, M.P., Colquhoun, D.J., and Siron, D., eds., Evolution
of the Atlantic Coastal Plain - Sedimentology, stratigraphy, and hydrogeology:
Sedimentary Geology, v. 108, p. 45-90.
Poag, C.W., 1999,
Chesapeake Invader: Discovering America’s giant meteorite crater: Princeton
University Press, Princeton, New Jersey, 183 p.
Poag, C.W. and Pope, L. J., 1998, The Toms Canyon
structure, New Jersey outer continental shelf; a possible late Eocene impact
crater,
in Poppe, L.J.,
ed., Marine Geology, Volume 145: Netherlands, Elsevier: Amsterdam, Netherlands,
p. 23-60.
Poag, C.W., and
Sevon, W.D., 1989, A record of Appalachian denudation in post-rift Mesozoic and
Cenozoic sedimentary deposits of the U.S. Middle Atlantic continental margin:
Geomorphology, v. 2, p. 119–157.
Poag, C.W.,
Powars, D.S., Poppe, L.J., and Mixon, R.B., 1994, Meteoroid
mayhem in Ole Virginny: Source of the North American tektite strewn field:
Geology, v. 22, p. 691-694.
Poag, C.W.,
Powars, D.S., Poppe, L.J., Mixon, R.B., Edwards, L.E., Folger, D.W. and Bruce,
S., 1992, Deep sea drilling project Site 612 bolide event: New evidence of a
late Eocene impact-wave deposit and a possible impact site, U.S. east coast.
Geology, v. 20, pp. 771-774. 1992. Poag, C.W., Powars, D.S., Poppe, L.J., Mixon,
R.B., Edwards, L.E. Folger, D.W., and Bruce, S., 1992, Deep
Sea Drilling Project Site 6122 bolide event: New evidence of a late Eocene
Impact-wave deposit and a possible impact site, U.S. East Coast:
Geology, v. 20, p. 771-774.
Ribiero, A., 2002,
Soft plate and impact tectonics: Springer-Verlag, Heidelberg, Germany, 327
pages.
Rickard,
L.V., 1973, Plate 18: Structure contours on top of Precambrian Basement,
Stratigraphy and structure of the Cambrian ad
Ordovician carbonates of New York; New York State Museum and Science Service,
Map and Chart Series 18, (26 plates, 10 sheets), scale 1:100,000
Roden M.K, Miller
D.S (1989) Apatite fission-track thermochronology of the Pennsylvania
Appalachian Basin. Geomorphology v. 2: p. 39–51
Sak, P.B., Gray,
M.B., and Ismat, Z., 2014, Significance of the deformational history within the
hinge zone of the Pennsylvania Salient, Appalachian Mountains: The Journal of
Geology, v. 122, p. 367-380.
Sharpton, V.L.,
and Ward, P.D., eds., 1990, Global Catastrophes in Earth History: An
interdisciplinary conference on impacts, volcanism, and mass mortality:
Geological Society of America Special Paper 247, 631 p.
Smith, R.C. II,
2003, Lead and zinc in central Pennsylvania. In: 68th Field Conference of
Pennsylvania, Geologists Guidebook, pp 63–72
Smith R.C.
II and Faill, R. T., 1994, The Mesozoic
heating event in the mid-Atlantic region, U.S.A:
Geological Society of America Abstracts with
Programs, v. 32, p. 75.
Snyder, S.L., 2005, Complete Bouguer anomaly map of
Virginia: U.S. Geological Survey:
http://pubs.usgs.gov/of/2005/1052/html/va_grav_large.htm.
Southworth, C.S.,
Gray, K.J., and Sutter, J.F., 1993, Middle Eocene intrusive igneous rocks of the
central Appalachian Valley and Ridge province; Setting, chemistry, and
implications for crustal structure: U.S. Geological Survey Bulletin 1839-J, p.
J1–J24.
Spang, J.H., and
Groshong R.H., Jr., 1981, Deformation mechanisms and strain history of a minor
fold from the Appalachian Valley and Ridge Province: Tectonophysics, Volume 72,
Issues 3–4, p. 323-342.
Steckler, M.S.,
Omar, G. I., Karner, G.D., and Kohn, B.P., 1993, Pattern of hydrothermal
circulation with the Newark basin from fission-track analysis: Geology, v. 21,
p. 735-38.
Stewart, I.S., and
Hancock, P.L., 1994, in Hancock, P. L., ed., Continental Deformation:
Neotectonics, New York, Pergammon Press, p. 370-409.
Thomas, W.A.,
1977, Evolution of salient and recesses from re-entrants and promontories in the
continental margin: American Journal of Science, v. 277, p.
Tollo, R.P.,
Corriveau, L., McClelland, J., and Bartholomew, M.J., 2004, Proterozoic Tectonic
Evolution of the Grenville Orogeny in North America, in, Tollo, R. P., ed.,
Proterozoic tectonic evolution of the Grenville orogen in North America,
Geological Society of America, 820 p.1-18.
Tso, J.L.,
McDowell, R.R., Avary, K.L. , Matchen, D.L., and Wilkes, G.P., 2004, Middle
Eocene igneous rocks in the Valley and Ridge of Virginia and West Virginia. In
Southworth, S., and Burton, W., eds., Geology of the National Capital Region –
Field Trip Guidebook: U.S Geological Survey Circular 1264, trip 4, p. 137 – 157.
Weems, R.M., and
Olsen, P.E., 1997, Synthesis and revision of groups within the Newark
Supergroup, eastern North America: Geological Society of America Bulletin, vol.
109, no. 2, p. 195-209.
Wise, D.U. and
Werner, M.L., 2004, Pennsylvania salient of the Appalachians: A two-stage model
for Alleghanian motion based on new compilations of Piedmont data: Geological
Society of America Special Papers, v. 383, p. 109-120.
Withjack,
M.O., Schlische, R.W., Malinconico, M.L., and Olsen,
P.E., 2013,
Rift-basin development: lessons from the Triassic- Jurassic Newark Basin of
eastern North America,
in Mohriak,
W.U., Danforth, A., Post, P.J., Brown, D.E., Tari, G.C., Nemcok, M. and Sinha,
S.T. , eds., Conjugate Divergent Margins. Geological Society, London, Special
Publications, 369, p. 301–321.