Transcript Newark Basin

Mesozoic Events
The Piedmont:
Newark Basin
The Mesozoic Era
Mesozoic Era = 251 to 65.5 million years ago.
 Name Mesozoic means "middle life"
 Mesozoic Era consists of three periods:
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Triassic - Oldest. Lasted about 51 million years
 Jurassic - Lasted about 55 million years
 Cretaceous - Youngest. Lasted about 80 million
years
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Pangaea
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At the beginning of the Mesozoic, the
continents were assembled into a
supercontinent, Pangea.
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Pangea formed in the Late Paleozoic by the
collision and joining of the continents to
form a single landmass surrounded by a
vast ocean.
Pangaea
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In the equatorial area to the east, between
Africa and Europe, and between India and
Asia, was an embayment called the Tethys
Sea.
The climate became arid; evaporites (E)
were deposited.
The Breakup of Pangaea
Pangea began to break up in the
Mesozoic.
 The northern continents were called
Laurasia and the southern continents
were called Gondwana.
 As North America and Europe
separated, they were called Laurentia
and Baltica.
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The Breakup of Pangaea
The breakup occurred in
four stages:
Stage 1:
 Rifting and volcanism along normal faults
in the Triassic, resulting in the separation of
North America (Laurasia) from
Gondwanaland.
 Normal faulting in eastern North America,
accompanied by the intrusion of dikes and
lava flows.
 Atlantic Ocean opened and widened
through the extrusion of oceanic basalts.
The continents did not split along the places
that marked their previous edges.
The old suture (or "seam") between North
America and Africa lies in southern Georgia.
When Africa pulled away, it left a sliver of
the African continent attached to the
southeastern U.S.
The Breakup of Pangaea
Stage 2:
 Rifting and separation of Africa, India, and
Antarctica.
 Large volumes of basalt were extruded.
Stage 3:
 The Atlantic rift extended northward.
 Eurasia moved to the south, partially closing
the Tethys Sea.
 South America began to split from Africa by the
Late Jurassic, and completely separated by the
Late Cretaceous.
 Australia remained connected with Antarctica.
 India was moving northward toward Asia.
 Greenland began to separate from Europe
(Baltica), but remained attached to North
America (Laurentia).
Stage 4:
 After the Mesozoic, the breakup of Pangaea
continued.
 North America (Laurentia) separated from
Eurasia (Baltica) along the North Atlantic rift.
 Antarctica and Australia separated about 45
m.y. ago.
The total time for the fragmentation of Pangea
was about 150 m.y.
The Triassic of Eastern
North America
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During the Triassic Period in eastern North America,
the Appalachian Mountain ranges were much higher
than they are today.
The mountains were eroding at the beginning of the
Mesozoic Era.
Coarse clastic sediments from the mountains filled
basins between the mountains during the Early and
Middle Triassic.
The Appalachians were reduced by erosion
throughout the Triassic, Jurassic and Cretaceous.
Triassic
Paleogeography
The Triassic of Eastern
North America
During the Late Triassic and Early
Jurassic, North America experienced
tensional stress and rifting.
 Fault-bounded rift basins developed in
eastern North America, extending
from Nova Scotia in the north to
Georgia in the south.
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Newark Supergroup
The fault-bounded basins filled
with Late Triassic and Early
Jurassic sediments eroded from
the Appalachians, and basaltic
lava flows and diabase
intrusions (sills and dikes).
These rocks comprise the
Newark Supergroup.
Four stages in the Triassic
history of the Connecticut Valley
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4.
Erosion of mountains
Low plain
Sediment deposition,
lava flows, and
intrusions in faultbounded basin
Post-depositional
faults
Newark Sediment
Deposition
The sediment in the Newark basins
was deposited in continental (nonmarine) sedimentary environments
such as:
Alluvial fans
 Rivers and floodplains (alluvial)
 Lakes (lacustrine)
 Deserts (aeolian or eolian)
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Newark Sediment
Deposition
The sedimentary rocks are primarily
red arkosic sandstone, siltstones, and
shales.
 Dinosaur bones and tracks are
present locally.
 Some of the lake deposits are black
and gray shales with the remains of
fish, aquatic reptiles, and freshwater
invertebrates.
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Newark Supergroup
Sedimentary Rocks
DINOSAUR TRACKS
CROSS BEDDING
Sedimentary Rocks
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While the Newark Basin was forming
sediments were carried into the valley by
streams (possibly intermittent streams during
times of desert-like climate conditions). The
sediments were deposited on alluvial fans and
on shallow water deltas the spread from the
surrounding upland areas into lakes that grew
and shrank with changing climatic conditions.
Volcanism occurred intermittently, both as
intrusions in the subsurface and flows on the
surface. Through time sediments accumulated
to great depths.
Today as much as 11,000 feet (or more) of
sedimentary rock and volcanic material of
Newark Basin probably exists beneath the
western side of the basin.
These red bed
consist of layered
flaggy sandstone
and intervening
shale that preserve
a variety of very
well preserved
sedimentary
structures (mostly
ripple marks and
dessication cracks)
and occasionally
trace fossils (rare
dinosaur tracks)
MUD CRACKS
Sedimentary Rocks
The sedimentary rocks of the Newark
Basin are subdivided into three thick
formations:
 the Stockton,
 the Lockatong, and
 the New Brunswick formations, oldest
to youngest, respectively.
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Newark Supergroup
Basaltic Lava Flows
Several Early Jurassic
lava flows are present
in most of the basins.
 Three particularly
extensive lava flows
and an imposing sill
(the Palisades sill) are
present in the New
Jersey-New York area.
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Volcanic Rocks
The mafic igneous bodies intruded
upward between sedimentary layers
forming sills and stocks, cooling in the
subsurface.
 The classic example of a volcanic sill
is the Palisades along the western
side of the Hudson River.
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Palisades Sill
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The Palisades along the western shore of the
Hudson River are created by the exposed
diabase sill, about 190 million years old.
Volcanic Rocks
The mafic volcanic material extruded
on the surface as surface flows.
 Most of the Watchung Mountains
throughout central New Jersey are
examples of extrusive igneous rocks,
displaying characteristic columnar
jointing and stacked lava flows.
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I-280 highway road cut through the columnar-jointed
basalt of 1st Watchung Mountain just west of Orange,
New Jersey.
Volcanic Rocks
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The mafic volcanic material erupted
beneath the surface of a lake or inland sea
flooding the basin area. The lava spread as
submerged flows, chilling quickly when in
contact with water forming "pillows" and
complex flow structures, similar to
submarine flows on Hawaiian volcanos or
along mid-ocean spreading centers.
Examples of pillow lava flows include parts
of the Watchungs, particularly in the vicinity
of Paterson and Morristown, New Jersey.
The beautiful zeolite minerals associated
with traprocks are most abundant in the
"fossil gas bubbles" associated with lava
pillows.
The falls spill over a resistant ridge into a chasm carved in the lower flow of
the Orange Mountain Basalt where it overlies the upper contact of the
Passaic Formation. In the vicinity of the falls, glacial erosion has stripped
away the upper more friable pillow lavas. These pillow lavas can be seen in
the abandoned traprock quarries throughout the hillsides in the Paterson
area
Example of a pillow lava in the Orange Mountain Basalt.
Cyclicity
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The rocks of the Newark Basin represent sediments deposited
concurrent with the movement of the border faults, the large
normal faults that created the half-graben structures
The raised foot wall of the border faults became the rugged
mountainsides that shed sediments into the adjoining basin areas.
Along the border fault large alluvial fans accumulated. These
deposits, consist of coarse sand to massive boulders cemented in
a fine, iron-rich matrix.
Towards the center of the basins, the coarser material vanishes,
and the sediment consists of evenly-layered fine-grained
sandstone, mudstone, and shale.
Repeating sedimentation patterns in the thick sequence of strata
within the basins reveals that long-term fluctuations in the climate
played an important role in the distribution and character
sediments.
At times, the climate was wetter, so large lakes expanded to
nearly fill the entire basin.
During extended dry periods, these lakes dwindled in size, or
vanished.
The dry lake beds became alluvial plains with migrating stream
channels.
Evidence for these cyclic changes, ranging in the order of 10,000s
to 100,000s years are recorded by both the character of the rock
and the fossils they preserve.
Coal
Coal is formed from plant remains.
 Triassic coal is present in Newark
Supergroup rift basins in North
Carolina and Virginia.
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