Marquez
Key facts
- Country
- United States
- Diameter
- 12.7 km
- Age
- 58 ± 2 million years
- Location
- 31.28° N, 96.30° W
Very little: a small patch of jumbled Cretaceous rock, about 1 km across, at the surface near the town of Marquez in Leon County, Texas. The rest is buried.
Marquez is a buried impact crater about 12.7 km across in Leon County, east Texas, in the United States. It formed in the Palaeocene, about 58 million years ago, some 8 million years after the impact that ended the age of the dinosaurs.
What it hit. The impactor struck a sequence of Cretaceous sedimentary rocks, limestones, sandstones and shales, near the coast of what was then a larger Gulf of Mexico. The crater was soon buried by younger sediments. The only surface sign is a small area of disturbed rock called Marquez Dome, where Cretaceous layers stick up through younger cover. This is the top of the crater's central peak, which rose more than a kilometre above the crater floor.
From salt dome to crater. East Texas has many salt domes, where a buried layer of salt has slowly risen, pushing up the rocks above. At first Marquez Dome was thought to be one of them. However, seismic surveys made for oil exploration showed no salt below, and instead revealed the shape of a buried crater with a central peak. Geologists then found shatter cones, cone-shaped fractures produced by shock, and quartz grains with shock features, confirming an impact.
Why it matters. Marquez shows how oil-industry seismic data and well logs can reveal hidden craters, and how easily an impact can be mistaken for a more familiar structure. The impactor is unknown.
Visiting. The area is private farmland and ranch land. Ask permission before entering.
Did you know?
Marquez was once thought to be a salt dome.
Its only surface sign is the top of a central peak, about 1 km across.
It formed about 8 million years after the dinosaur-killing impact.