New Jersey is a geologically situated region in the United States. Its statewide metric geological map was first published in United States. New Jersey is subdivided into three tiles, south, central and north. Relief on the bedrock surface in the Northern Jersey indicates relative resistance of highly valuable rock units to erosion. Many process that occur on the earth surface play crucial role in shaping the bedrock surface- like prolonged preglacial periods and interglacial fluvial erosion, marine and slope erosion, postglacial fluvial erosion and rock weathering. Northern New Jersey has diverse geology compared to southern part. Geological features in Northern New Jersey have impacted the course of industry, settlement, development and commerce in the region. The essay discusses geology in Northern New Jersey and the event which led to formation of sterling mine.
The northern part occupies two-fifth of the total area of New Jersey State- 20,168km 2 . This region is underlaid by formation of the rocks in three ground water provinces where fissure water conditions prevail. The provinces are, (1) highlands- with parsley settled valleys and ridges of Precambrian granites and gneisses with infolded Paleozoic slates and quartzite, (2) Piedmont of lava flows, Triassic shales and sandstones, that constitute the most population of the New Jersey, and (3) valley and ridges- which is the smallest province in the state located at the northwest corner of New Jersey. It is a province of Paleozoic limestone and shales of agriculture ( Salisbury, 2017 ) .
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The geological events in the highlands province in the northern part of New Jersey State have been occurring for over billion years ago; they continue to shape the populated landscape. Its’ distinctive elevations, rocks, landforms and other geographical features creates irreplaceable and unique region whose geology is hundreds of millions years old ("Surficial Geologic Map of Northern New Jersey,") .
The oldest development in this region is said to have transpired between 1.3 to 1 billion years ago during the Grenville orogeny event of the Precambrian time ("Surficial Geologic Map of Northern New Jersey," 2002) . The process involved change in tectonics, a number of continental plates impinged on, which led to creation of folded mountains in the eastern part of North America. The ancient rocks are the underlying bases of all the highlands geological features covered by the young rocks. Due to high temperatures and extreme pressure in this region, buried dolomite, mudstone, sandstone and granite were easily changed to gneiss while limestone transformed into marble.
Around 900 million years ago, the collision of plates caused ocean basins to form underwater continents. Later about 550 million years ago, new Jersey State begun to rise, covered by the tropical seas that integrated into oceanic depth. Although the activities of the plates stopped later, rivers did not cease to deposit huge amount of gravel and sand which contributed to the erosion of the latest mountain ranges ( Salisbury, 2017 ) . The old materials serve as underground foundation of the present mountain ranges in the highlands province.
Ridge and valley is the smallest province in the northern part of the New Jersey. One part of the great Appalachian valley is Kittatinny valley which contains some of the oldest rocks- Martinsburg shale, created during Ordovician period. At the periphery of this valley, there is Kittatinny Ridge which measures about 1500-1800 feet. The province is underlain by folded and faulted layers of limestone, shale and sandstone that range between 570-345 million years of age. Initially, the rocks were sand, lime and mud sediments which were loaded in erstwhile floodplains and seas ( Salisbury, 2017 ) . The intrusions were distorted by compaction into thrust, folds and faults during different times (Ordovician, Pennsylvanian and Permian times). Due to deformations, the sedimentary which were originally flat were tilted.
The alternation of the belts of easily eroded shale, limestone and erosion resistant sandstone creates the long, parallel ridges and valleys running from north-east to south-west. The resistant siltstone and sandstone layers form the base for Walpack Ridge and Kittatinny Mountain; limestone and shale form the base for the valley of flat brook, the broad valley between Kittatinny Mountain and the highlands to the west and the Delaware valley upstream from the Delaware water gap ( Salisbury, 2017 ). The limestone is quarried to provide construction materials.
Piedmont carries the highest population in New Jersey State. Piedmont is overlaid by the Stockton sandstones and the Triassic Brunswick Shales which provide water to the population. However, various research in industrial wells indicate that sandstone gives about 20% more water compared to shales. Series of major faults separate rocks of the highland and Piedmont provinces. According to the research, it is indicated that more resistant gneisses and granites on the northwest side of the fault creates big escarpment which is about 200-800 feet in height (Salisbury, 2017) .
The geology of Northern New Jersey is believed to be influenced by three recurring cycle periods of glacier flows during the ice ages. The last intrusion happened 21,000 years ago which was marked by glaciers expanding from the north and then receded as temperature rose. The glacial flush pushed carved valleys, rock and soil in their way, boulders, eroded bedrocks and flattened hills and created a way as far south as parts of the today’s Somerset, Hunterdon and Middlesex states (Salisbury, 2017) .
Events which formed Sterling mine
Sterling Hill Mine currently referred as Sterling Hill Mine Tour and Museum of Fluorescence is well known for extraction of iron and zinc years ago. It transformed to museum in 1989 along with other mining sites. Further, as Wolfe (1977) affirmed, it is known to have variety of minerals, especially the fluorescent varieties. The Sterling mine of Ogdensburg has produced over 11 million tons of zinc ore. The question that arises is the origin or the source of these mineral deposits.
Various scholars had problems coming to consensus about the origin of the deposits in the sterling mine. However, it is agreed that the sediments at Sterling Mine happened about 1.3 billion years ago. It started as hot fluids of metal-rich layers released or channeled onto the surface of a shallow sea. At that time, the floor of the sea was covered by white muds of calcium carbonate, which is the present situation in Bahama Banks (Davis, Leavens, & Jenkins, 2012) . As the hot flow combine with cold sea water, the minerals dissolve in water and precipitate as small grindings which later fall to the surface of the sea, there it accumulate as layers of metals within the thick series of white muds of carbonate.
It is justifiable that the deposits originated from collision of the oceanic plate and continental plate (Gordon, 2005) . Because continental plate is lighter than oceanic crust, the continental plate override the oceanic crust which then descends bellow the continental plate. As the continental plate dives beneath the continental plate, partial melting takes place to create series of volcanoes that release sediments into shallow sea. The area beneath the earth’s crust is stretched. The expansion create fracture zones which allow overheated metalliferous brines (magma) to rise and pass through the shallow depth and emerge on the surface of the sea, where it forms series of deposits of metal-rich muds (Gordon, 2005) . This is exactly what happened about 1.3 billion years ago, when the residues of calcium carbonate and the layers of metal-rich muds were first loaded.
As the plates continued to collide, the sediments in Sterling were gradually buried and finally reach depths of 15-18km and melted to a temperature of about 800 degrees Celsius. The muds of carbonate transformed slowly into limestone. The rocks continued to descend, with increased pressure and heat; limestone changed slowly into marble and the metal-rich layers transformed to ore of zinc minerals (franklinite, willemite, and zincite) that exist currently at the Sterling Hill Mining Museum (Gordon, 2005).
Conclusively, the northern part of New Jersey consist of three provinces- Ridge and Valleys, Highlands, and Piedmont provinces. The northern part of New Jersey has distinctive features like landforms, rocks, elevations and other geographical features which gives it special characteristics, and obtains cultural differences from the southern part of the state. The ores in the Sterling mines resulted from deposits of limestone in a Precambrian oceanic rift trough, which continuously underwent extensive transformation during Grenville orogeny about 1 billion years ago.
References
Davis, K. L., Leavens, P. B., & Jenkins, R. E. (2012). Sphalerite from the Sterling Hill Mine, New Jersey: Origin and History. The Journal of Geology , 120 (2), 203-216. doi:10.1086/663982
Gordon, R. B. (2005). Mine Hill in Franklin and Sterling Hill in Ogdensburg, New Jersey: Mining History, 1765-1900 (review). Technology and Culture , 46 (4), 843-844. doi:10.1353/tech.2006.0012
Salisbury, R. D. (2017). The Glacial Geology of New Jersey (Classic Reprint) . Forgotten Books.
Surficial Geologic Map of Northern New Jersey. (2002). doi: 10.3133/i2540c
Wolfe, P. E. (1977). The geology and landscapes of New Jersey .
