Faults Fractures in rock Normal Faults Reverse fault –Thrust fault- low angle reverse fault Strike-Slip fault –Left-lateral vs. right-lateral
Introduction Mountain Major mountain belts Mountain range
Characteristics of Major Mountain Belts Size and Alignment Along continental margin Long, arcuate chains Ages of Mountain Belts and Continents –Youngest tend to be higher –Himalayas vs Appalachians –Craton- Oldest Continental Crust Precambrian Shield
Characteristics of Major Mountain Belts Patterns of Folding and Faulting –Fold and Thrust Belts Crustal Shortening Crustal Thickening Metamorphism and Plutonism Normal Faulting
Evolution of a Mountain Belt Accumulation Stage of Sediments –Accumulation in an Opening Ocean Basin –Accumulation along a Convergent Boundary Graywackes Magmatic Arc Mountain Building Event- Orogeny
The Growth of Continents Crust added by accumulation & igneous activity Suspect and Exotic Terranes –Suspect terrane –Accreted terrane Exotic terrane
The Wilson cycle (named after J. Tuzo Wilson, one of the fathers of plate tectonics) refers to the cycle of ocean basin formation by rifting and seafloor spreading followed by ocean basin destruction and mountain building by subduction.
Geologic Evolution of Eastern North America
THE EARLY PALEOZOIC THE CAMBRIAN MY CAMBRIA>>WALES ADAM SEDGWICK 1835 THE ORDOVICIAN MY ORDOVICE>>WELSH TRIBE CHARLES LAPWORTH 1879
TECTONIC EVENTS Overall scenario is coalescence of Pangea during most of the Paleozoic Taconic Orogeny mid to late Ordovician Caledonian Orogeny late Silurian to early Devonian Acadian Orogeny mid Devonian Alleghenian Orogeny late Penn, Permian Hercynian Orogeny - Ouachita Orogeny
PLATE TECTONIC MOVEMENTS FROM THE NEOPROTEROZOIC TO THE DEVONIAN (750 MY TO 370MY) BREAK UP OF RODINIA AVALONIAN OROGENY OPENING OF IAPETUS OPENING OF RHEIC TACONIC OROGENY CLOSING OF IAPETUS ACADIAN OROGENY
The Appalachians Valley and Ridge –folded & faulted sedimentary rocks Blue Ridge Province –metamorphosed Precambrian and Paleozoic Rks Inner Piedmont –high grade metamorphic rocks intruded by granites Charlotte & Carolina Slate Belt –metamorphosed & folded late Proterozoic & Cambrian sediments and volcanics
A) Cambro-Ordovician Passive Margin: Sandy Shelf Deposits B) Middle to Late Ordovician Development of Trench Along the Eastern Boundary and Subsequent Closure of the Iapetus Ocean C) Collision of Island Arc and other Accreted (exotic) Terranes with North America in the TACONIC OROGENY
CAMBRIAN PALEOGEOGRAPHY: SHALLOW EPICONTINENTAL SEAS COVERED THE CENTRAL US Earliest Paleozoic time of lowest sea level due to Proterozoic glaciations By middle Cambrian sea had flooded the continent
LITHOLOGIC FACIES OF THE CAMBRIAN
NEOPROTEROZOIC TO CENOZOIC TRANSGRESSIONS AND REGRESSIONS OBSERVED ON THE CRATON Variable sea level represented sequences of sediments bounded by unconformities on all of the cratons - e.g. Sauk, Tippecanoe
ORDOVICIAN- PALEOGEOGRAPHY Tippecanoe Transgression St. Peter’s Sandstone
The Queenston Clastic Wedge Redbeds coarser towards the source area, Taconic Highlands (4000m)
Early Paleozoic Climates Climates overall warmer than today Continents 60 0 N & S of equator Arid to sub arid environments 45 0 N & S of equator Redbeds (alluvial) 30 0 N & S of equator Tropical reefs 30 0 N & S of equator –Cambrian Archeocyathids; Ordovician Bryozoans Glaciation during the late Ordovician in Africa
THE MIDDLE PALEOZOIC THE SILURIAN MY SILURES>> WELSH TRIBE Roderick Murchison 1835 THE DEVONIAN MY (Old Red Sandstone) DEVON>> County in SW England Roderick Murchison Adam Sedgwick 1839
INTRODUCTION Final Collision and Suturing of Baltica and Laurentia Caledonian and Arcadian Orogenies High Stands of Sea Level Epicontinental seas; marine deposits and thick sequences of evaporites Reefs became important
PALEOGEOGRAPHY Closing of Iapetus Ocean –Baltica-Laurentia; Mongolia-Siberia Closing of Rheic Ocean as Gondwana migrated to west (Laurentia/Baltica-Gondwana) Laurentia continued to be a tropical craton Shallow seas covered the continents during much of Silurian Devonian orogenies in Northern Hemisphere –Caledonian (Scandinavia/Greenland) & Acadian (New England)
Cratons and Mobile Belts of North America and Europe
TECTONIC EVENTS Caledonian & Acadian Orogenies –Extension of Late Ordovician Taconic Orogeny Mid Devonian Iapetus Ocean closed Baltica collided with Laurentia Avalonia (Island Arc) sutured to both Baltica and Laurentia
Orogenic Development Of the Eastern US Acadian Orogeny produced a thick clastic wedge (the Catskill Wedge) of red beds [conglomerates and sandstones]
During the Devonian the rate of sedimentation increased from 7m/MY to 17m/MY to 70m/MY Chattanooga Shale- Anoxic black shale, marker bed East-West Cross Section across the Devonian Catskill Wedge
Lithofacies & Thickness Map of the Upper Devonian Sequence of the Eastern US
The Appalachians Valley and Ridge –folded & faulted sedimentary rks Blue Ridge Province –metamorphosed Precambrian and Paleozoic Rks Inner Piedmont –high grade metamorphic rks intruded by granites Charlotte & Carolina Slate Belt –metamorphosed & folded late Proterozoic & Cambrian sediments and volcanics
Physiographic Provinces of the Appalachian Region
Oriskany Sandstone Kaskaskia Transgression
Mineral Deposits Sedimentary copper, silver, lead and zinc sulfides and Iron ores Occur in shales and carbonates Disseminated or interbedded New York to Alabama
Stokes Forest The area around Stokes Forest has a long history of mining attempts; none of them proved to be significant. Mine prospects in the area have yielded traces of lead, silver, gold and copper, but not in economically recoverable amounts. One operation, the Snook Mine, was dug in the 1880s by its proprietor, John Snook, who actually discovered a vein bearing silver ore. He reported to have been paid $75.00 per ton for his ore.
Green Pond Outlier The Green Pond Outlier is a complex northeast-trending belt of Paleozoic sedimentary rocks that bisects the Precambrian crystalline rocks of Reading Prong (Highlands Province), and extends for 65 miles between I-80 in New Jersey and the New York Thruway in New York. The sedimentary rocks within this belt are folded into a complex synclinorium in which the beds are locally completely overturned, particularly in the New York end. The Green Pond Outlier correlate to equivalent units in the Valley and Ridge region. Green Pond Quartzite, an alluvial conglomerate which accumulated unconformably on an irregular surface of Precambrian. It is a massive conglomerate and cross-bedded sandstone equivalent in age to the Shawangunk
Green Pond Outlier By Late Silurian time the coarse clastic deposition gave way to finer-grained mud (represented by the Longwood Shale), and eventually to shallow marine carbonate deposition (Poxono Island and Berkshire Valley Formations). The total thickness of the Silurian section is approximately 1,500 feet.
Green Pond Outlier In the Green Pond Outlier, the Early Devonian is not represented (the entire Helderberg Group is missing). Middle Devonian strata rest unconformably on the surface top of the Silurian section. The base of the Devonian sequence is represented by the Connelly Conglomerate, an equivalent stratigraphic unit of the Oriskany Sandstone which crops out throughout the Appalachian Basin region. The Connelly Conglomerate is overlain by a sequence of Middle Devonian shale and sandstone formations that locally bear marine invertebrate fossils. In ascending order, the Middle Devonian units include Esopus Formation, Kanouse Sandstone, Cornwall Shale, and Bellvale Sandstone. This Middle Devonian sequence approaches about 3,000 feet thick.
Appalachian Valley and Ridge The erosional characteristics of the sedimentary rock formations exposed along great anticlines and synclines of the Appalachian Mountains are responsible for the characteristic Valley and Ridge topography. Durable layers of sandstone and conglomerate form ridges, whereas less resistant limestone and shale underlie the valleys in the region. Along the eastern margin of the Valley and Ridge is the Great Valley, a broad valley underlain by Cambrian and Ordovician shale and carbonate rocks that weather and erode faster that more durable sandstone and conglomerate that crop out in ridges and plateaus to the west
Kittatinny Mountain represents the eastern-most hogback ridge of Middle Paleozoic rocks of the Valley and Ridge
Aftermath of Taconic Orogeny As the Taconic Orogeny subsided in early Silurian time, uplifts and folds in the Hudson Valley region were beveled by erosion. Upon this surface sediments began to accumulate, the evidence for this is the Silurian Shawangunk Conglomerate, a massive, ridge- forming quartz sandstone and conglomerate formation, which rests unconformably on a surface of older gently- to steeply-dipping pre- Silurian age strata throughout the region. This ridge of Shawangunk Conglomerate extends southward from the Hudson Valley along the eastern front of the Catskills. It forms the impressive caprock ridge of the Shawangunk Mountains west of New Paltz, New York and west it becomes the prominent ridge-forming unit that crops out along the crest of Kittatinny Mountain in New Jersey. The deposition of coarse alluvial sediments gave way to shallow marine fine-grained muds, and eventually to clear-water carbonate sediment accumulation with reefs formed from the accumulation of calcareous algae and the skeletal remains of coral, stromatoporoids, brachiopods, and other ancient marine fauna.
Acadian Orogeny The Acadian Orogeny is the name of a long-lasting mountain building disturbance that most greatly affected the Northern Appalachian region (New England northeastward into the Gaspé region of Canada). The "climax" of this orogeny is dated as early in the Late Devonian, but deformation, plutonism, and metamorphism related to this orogeny continued well into the Mississippian Period. The cause of this great period of deformation is a result of the platedocking of a small continental landmass called Avalonia (named after the Avalon Peninsula of Newfoundland). The docking of Avalonia onto the margin of ancestral North America (referred to as Laurentia) resulted in the closing of a portion of the Iapetus Ocean
AVALONIA The Acadian Orogeny spanned a period of about 50 million years (beginning roughly 375 million years ago). During the coarse of the orogeny, older rocks were deformed and metamorphosed, and new faults formed and older faults were reactivated. Avalonia was gradually torn apart as plate tectonic forces accreted the landmass onto the edge of the larger North American continent. Today, portions of the ancient Avalonia landmass occur in scattered outcrop belts along the eastern margin of North America. One belt occurs in Newfoundland, another occurs along the western Bay of Fundy into eastern Maine. A large piece of Avalonia forms the bedrock of much of eastern Massachusetts, Rhode Island, and eastern Connecticut. Equivalent landmass material is preserved as an extensive belt of rock known as the Carolina Slate Belt which extends from Virginia southward into Alabama.
Acadian Orogeny As the Acadian Orogeny progressed, greater quantities of coarser clastic sediments migrated into shallow sea, building an extensive alluvial plain along the eastern margin of the seaway. The Catskills region was proximal to the Acadian Highlands, and therefore was the site of the greatest accumulation of sediment in the region. (The boundary between the two geologic regions is a line approximating the location of the modern Hudson River.
The Alleghenian Orogeny During late Paleozoic time the ancient Iapetus Ocean (also called Proto-Atlantic Ocean) continued to vanish as the North America continent (Laurentia) collided with Africa (which was part of a larger collection of continents called Gondwanaland). As the continents collided, the rock material trapped in-between was crushed and forced upward into a great mountain range, probably similar in size and character of the modern Alps. With nowhere to go, rocks along the eastern margin of the North American continent were shoved far inland (the same occurred in the opposite direction along the margin of the African continent, forming the Atlas Mountains of Morocco and the western Sahara).
The Alleghenian Orogeny As the two continents collided, large belts of rock bounded by thrust faults piled one on top another, shortening of the crust along the eastern edge of North America in the North Carolina and Tennessee region by as much as 200 miles. The relative amount of deformation gradually diminishes northward. The fold belt extends northward through Pennsylvania and gradually peters in the vicinity of the New York border. The Kittatinny Mountains in northwestern New Jersey mark the northeastern-most extension of the high ridges of the Valley and Ridge Province.
Aftermath A great unconformity beneath the Triassic sedimentary rocks of the Newark Basin series represents an extensive period of erosion of uplifted rocks and sediments during and after the Alleghenian Orogeny. In the New York Bight region, this unconformable surface is flooded beneath the lower Hudson River below the Palisades, and in New Jersey it is covered by younger sediments of the Coastal Plain.