New York exists on bedrock that tells a tale of millions of years ago, going as far back as the late Mesoproterozoic (1.6 to 1 billion years ago). The layers that make up this bedrock show the conditions of the earth’s surface through many different orogenies, which are times of high grade metamorphism and where plate tectonics makes its biggest changes.
The Fordham gneiss was formed a billion years ago (oldest) during the Grenville orogeny (Precambrian) which featured sediment deposits and volcanic activity, which marked the creation of the supercontinent Rodinia (Keary, 2009). Following the Grenville orogeny there was a period of erosion which allowed for a smooth surface for more deposition. When Rodina began to break up by the Iapetus ocean opening through rifting, led to volcanism. As the ocean opened it gave the conditions for the limestone and dolomite to form, which would then become Inwood Marble.
During the Taconian orogeny the mountains formed which restricted ocean circulation which produced the conditions for further deposition. The unconformity separated the gneiss from the marble. When the ocean began to again close, an island arc was formed and the carbonate that was …show more content…
The outcrop featured large garnets, anatexis was observed which shows two generations of garnets, pointing to the fact that there was differential or partial melting taking place (an indicator that it was an amphibolite facies). There was also evidence of a fault; the St. Nicolas fault which brought the Manhattan schist. There were observations of boudins of quartz, which are kinetic indicators of movement and stress on the rocks (Flores, 2016). In the Manhattan schist basaltic intrusions were also observed and contact of the intrusion zone. The pegmatites, which are igneous rocks, observed pointed to the Acadian orogeny which followed the
The Fordham gneiss was formed a billion years ago (oldest) during the Grenville orogeny (Precambrian) which featured sediment deposits and volcanic activity, which marked the creation of the supercontinent Rodinia (Keary, 2009). Following the Grenville orogeny there was a period of erosion which allowed for a smooth surface for more deposition. When Rodina began to break up by the Iapetus ocean opening through rifting, led to volcanism. As the ocean opened it gave the conditions for the limestone and dolomite to form, which would then become Inwood Marble.
During the Taconian orogeny the mountains formed which restricted ocean circulation which produced the conditions for further deposition. The unconformity separated the gneiss from the marble. When the ocean began to again close, an island arc was formed and the carbonate that was …show more content…
The outcrop featured large garnets, anatexis was observed which shows two generations of garnets, pointing to the fact that there was differential or partial melting taking place (an indicator that it was an amphibolite facies). There was also evidence of a fault; the St. Nicolas fault which brought the Manhattan schist. There were observations of boudins of quartz, which are kinetic indicators of movement and stress on the rocks (Flores, 2016). In the Manhattan schist basaltic intrusions were also observed and contact of the intrusion zone. The pegmatites, which are igneous rocks, observed pointed to the Acadian orogeny which followed the