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: Triassic - Oldest. Lasted about 51 million years Jurassic - Lasted about 55 million years Cretaceous - Youngest. Lasted about 80 million years

Pangaea At the beginning of the Mesozoic, the continents were assembled into a supercontinent, Pangea. 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 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.

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 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.

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 1. Erosion of mountains 2. Low plain 3. Sediment deposition, lava flows, and intrusions in fault- bounded basin 4. Post-depositional faults

Newark Sediment Deposition The sediment in the Newark basins was deposited in continental (non- marine) sedimentary environments such as: Alluvial fans Rivers and floodplains (alluvial) Lakes (lacustrine) Deserts (aeolian or eolian)

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.

Newark Supergroup Sedimentary Rocks DINOSAUR TRACKS

CROSS BEDDING

Sedimentary Rocks 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.

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.

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.

Palisades Sill 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.

I-280 highway road cut through the columnar-jointed basalt of 1st Watchung Mountain just west of Orange, New Jersey.

Volcanic Rocks 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 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.