Precursor Basin

In Their Own Story

The Permian Basin is the thickest deposit of Permian-aged rocks on Earth, rapidly deposited during the collision of North America and Gondwana between the late Mississippian through the Permian. It also includes formations dating back to the Ordovician Period, 445 million years ago. The basin's depositional history begins with the Proterozoic Tobosa Basin, containing basement rock dating back to 1,330 million years ago, visible in the present-day Guadalupe Mountains. The basement rock includes biotite-quartz granite discovered at a depth of 12,621 feet. The entire area is underlain by layered mafic rocks of the Pecos Mafic Igneous Suite, dated to 1,163 mya. During the Ordovician Period, the Montoya Group formed, described as light to medium grey, fine to medium grained crystalline calcareous dolomite, sometimes inter-bedded with shale, dark-grey limestone, and chert. The Silurian Period saw the Fusselman Formation (light grey, medium to coarse grained dolomite, 49 to 164 feet thick) and the Wristen Formation (mud, shale, and dolomite, reaching 1,480 feet thick). The Devonian Thirtyone Formation featured limestone, chert, and shale beds with a peak thickness of 980 feet. The Mississippian Period developed the Mississippian Limestone (49 to 171 feet thick, brown to dark brown micro-crystalline limestone) and the Barnett Shale (silty brown shale and fine-grained sandstone, 200 to 460 feet thick). The Ouachita Orogeny during the Late Mississippian led to folding and faulting that divided the Tobosa Basin into three sections.

Did You Know?

• The Permian Basin produced an average of 4.2 million barrels of crude oil per day in 2019.
• It is named after the Permian geologic period, the final period of the Paleozoic era.
• The basin covers more than 86,000 square miles (220,000 km²).
• The basement rock in the Guadalupe Mountains dates back to 1,330 million years ago.
• The Hovey Channel was originally an anticline formed during Precambrian faulting.