Over the years, Dallas has become a hub for energy business. Though there isn’t much direct exploration or production activity near the city, its proximity to the Permian Basin and friendly corporate environment have drawn several industry pioneers to call the Dallas-Fort Worth metropolitan area their headquarters: Kelcy Warren’s midstream icon Energy Transfer, fellow midstream leader Enlink, upstream companies Hunt Oil, Matador Resources, Pony Oil, and Aetheon, and downstream giant Comstock Resources. Southern Methodist University has also become widely known for its energy-focused MBA programs, attracting the next generation of industry leaders.

On the city’s eastern outskirts, the small town of Rockwall takes its name from geological intrigue. Rockwall is built upon a row of hard mineral stones that appear to be stacked up in what looks like a rock wall. For nearly two centuries, many have debated if the “wall” is a naturally occurring phenomenon or constructed by prehistoric men. Most geologists agree it is naturally occurring, including researchers at The University of Texas at Dallas and the Colorado Geological Survey. Though many believe the mystery has been solved, the town is still worth a stop next time you are visiting or doing business in Dallas-Fort Worth.

The Great Debate: Is It Natural?

Much of the wall has been excavated or accidentally uncovered, though not all.

  •  A section of the wall was first discovered in 1852 by Benjamin Boydstun, Terry Utley Wade, and William Clay Stevenson, according to the Rockwall Historic Foundation.
  •  Nearly 20 years later, geologist Richard Burleson examined the sections discovered and concluded they were “igneous occurrences.”
  •  In 1901, Texas geologist Robert T. Hill claimed they were clastic sand dykes.
  •  The phenomenon was covered in the media for the next 20 years. It was proposed to have been built by a prehistoric race in 1925, but two years later, experts from the Smithsonian Institute declared it natural.
  •  It first became a tourist attraction in 1936, averaging 70 visitors per day.
  •  In 1950, James L Glenn threw into question the possibility of the wall being built by a historic race, saying, “The fact that there is a natural fault here does not preclude the construction of other walls by a prehistoric race within the same region.”
  •  Nearly 10 years later, John T. Lonsdale refuted Glenn’s idea, as no known fault system runs through Rockwall County.
  •  In 1979, Kenneth Shar from The University of Texas at Arlington excavated two sections with a group of students. He concluded those two sections were naturally occurring but did not rule out the possibility that other sections could have been built by a prehistoric race.
  •  In 1988, geologist Brooks Elwood concluded that the wall is natural, based on his studies of three different sections.
  •  Architect John Lindsay claimed, “evidence of a prehistoric structure built by man is mounting,” based on his review of records, research, data, and documentation in 1996.
  •  The show “America Unearthed” examined one section of the wall and concluded it was naturally occurring.

Geology

Recent sources note the vast majority, 61, of the dikes in the wall are made of sandstone, five are made of limestone, and two are made of marcasite.

One source said, “The sandstone dikes are of well-sorted, subangular, fine quartz grains cemented by calcite. Sandy clay squeezed between the fractured sandstone blocks, from an underlying layer of sediment, and was cemented by calcite. The sandstone blocks were likely fractured as a result of tectonic activity and then injected by this fluid-like underlying sandy layer, which eventually cemented. This caused the dikes to take on the appearance of a masonry wall with semi- routine sandstone blocks held together by mortar. These sandstone dikes formed during the upper Cretaceous period, and are assumed to be between 85 and 87 million years old.”