The Hartford Basin
The Hartford Basin is a term that refers to the large area of mesozoic bedrock in the central part of the state of Connecticut. The bedrock in this area is significantly younger than the surrounding parts of the state even though the rocks it contains are around 200 million years old. Due to this area being topographically lower than the surrounding highlands, it is sometimes called the Central Lowlands.
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The basin formed as the land was being pulled apart during the breakup of the super-continent of Pangaea. During this process, large faults formed and caused huge areas of land to subside. Low areas formed by this subsidence were filled in with sediments from the mountains on either side of the basin, and with lava and magma that violently welled up from below. As a result the Hartford Basin, and others like it, now provide geologists with an opportunity to study sedimentary and igneous rocks that formed during this tumultuous time in Earth's past.
Arkose Sandstone
This is an example of sandstone that formed from the compaction and cementation of sediments that were shed off the ancient Connecticut highlands 200 million years ago. It is a piece of the formation known as the New Haven Arkose, one of a handful of sedimentary units that filled the subsiding basin during the Late Triassic and Early Jurassic periods.
Arkose sandstone is a specific type of sandstone that contains unusually high amounts of the mineral feldspar. Feldspar is a common mineral in the Earth's crust. However, it weathers quite quickly. Therefore, in order to survive sediment transport and incorporation into a sedimentary rock, it must be buried quickly so that it doesn't deteriorate. This is exactly what happened during the formation of the New Haven Arkose. The sediment was shed off of the mountainous highlands and deposited so quickly that feldspar and even whole rock fragments had no time to deteriorate.
Ancient Cobble
This piece of granite was found as a single clast that had weathered out of the New Haven Arkose sandstone. It formed as a sharp, angular piece of granite crumbled off of the mountainous, mesozoic highlands and became rounded into a cobble by fast-flowing monsoon flood waters during the Late Triassic period. It became incorperated into the conglomeratic sand of the New Haven Arkose.