User:Bcrawf123/Black Diamond Mines Regional Preserve

Indigenous Peoples' History
Long before the widespread ranching and mining activity that took place in the area, indigenous peoples had a presence in the Bay Area for 13,000 years. Three Bay Miwok tribes, the Chupcan, Ompin, and Volvon, lived in the areas surrounding the Black Diamond Mines Regional Preserve. The Chupcan occupied territory to the west of the preserve near Concord, the Volvon occupied the territory to the south including much of Mount Diablo, and the Ompin occupied the area to the north including Pittsburg, Collinsville, and the intervening waterway. Black Diamond Mines Regional Preserve is located in a boundary area between these three tribes. At the beginning of the 19th century, these three tribes were significantly impacted by the Spanish mission system. Between 1804 and 1806, the majority of Volvon Bay Miwok were split up and baptized at either Mission Dolores or Mission San Jose. A Spanish military raid caused the Chupcans to flee to Suisun territory in 1804, and by 1811, most Chupcans were split up and baptized at either Mission Dolores or Mission San Jose. In 1810, some members of the Ompin went to Mission Dolores, and the remaining members went to Mission San Jose in the years 1811 and 1812.

Geological History


The rich coal deposits and sandstone hills of Black Diamond Mines Regional Preserve were formed by geological activity in the Tertiary period. In the period between the Paleocene epoch and Miocene epoch of the Tertiary era, the North American Plate and the Pacific plate came together at a subduction zone where the North American Plate was pushed over the Pacific Plate. During this era, the Pacific Ocean stretched over much of the California central valley, with the coastline reaching the lower regions of the Sierra Nevada mountains. Tectonic activity between the North American and Pacific plate, along with sea level changes, brought about four series of marine sediment deposition. The coal that was mined from the Mount Diablo Coal Field was formed during the third marine sediment deposition cycle, which took place during the middle of the Eocene epoch. At the beginning of this third cycle, tectonic activity caused an uplift of the continental shelf seafloor, resulting in the creation of shallow marshes. Erosion during this era brought an abundance of sediment into the shallow sea covering the continental shelf, with some sediment making its way into the marshlands. These sediments, along with the favorable hot and humid climate, fueled the growth of coastal marsh flora that eventually formed into coal. Tectonic activity towards the end of this sedimentation cycle caused the continental shelf to sink and resulted in sediments being deposited into deeper water. The Mount Diablo Mountain Range of today was created at the beginning of the fourth depositional cycle when the continental shelf began to rise up once again.