Issue 038 | August 2019          

Dallas's Rocky Past 
In the Metroplex, while ancient igneous and metamorphic rocks lie hidden deep beneath the earth's surface, sedimentary rocks deposited later in the geologic time scale sometimes reveal themselves through exposed outcrops from formations such as the Cretaceous period's Austin Chalk. The Dallas Paleontological Society article "Geology of Dallas and Tarrant County" identifies the formations represented on the surface for the two counties, as well as providing an introductory guide to understanding the sedimentary record. For those wanting to dig deeper into Dallas's geology, and its influence on early development of our city, see Geology of the Dallas-Fort Worth Metroplex : a Primer, by University of Texas at Dallas geosciences professor Robert J. Stern.
 
Rocky Relationships
The scientific disciplines of stratigraphy and paleontology are interdependent in helping us understand the earth's history. The previously mentioned group
Dallas Paleontological Society provides an opportunity for professionals and serious amateurs to meet to exchange ipaleontology-related information.  The group also provides field trip opportunities such as an August 2019 trip to Oliver Creek in Justin.
Exposed For All to See
One locale for appreciating Dallas's geology, Cedar Hill's Dogwood Canyon Audubon Center, provides a glimpse of the White Rock Escarpment, as well as a nearby vista where the Eagle Ford Shale formation can be seen in relation to the Austin Chalk formation. Additional formation exposures can be viewed at various spots in Dallas County.  White Rock Creek (north of central Dallas) and Tenmile Creek (south of central Dallas) both include spots where exposure of Austin Chalk is observable.
  
Citizens Helping Geologists
The most recent small earthquake felt in DFW occurred just a month ago in the Tarrant County town of Rendon.  If you ever experience an earthquake, you can assist the United States Geological Survey (USGS) by completing an online survey Did You Feel It? (DYFI.), which asks questions such as "how would you describe the shaking?" and "did objects rattle, topple over, or fall off shelves?" Data collected from the DYFI system is used for a variety of  scientific applications.
 
Access our Podcast!
We invite you to deepen your knowledge of the beautiful natural world that is all around us and to connect with passionate naturalists by listening to our bi-weekly podcast. All in the spirit of lifelong learning!
 
Featured Books 
Aerial geology : a high-altitude tour of North America's spectacular volcanoes, canyons, glaciers, lakes, craters, and peaks
by Mary Caperton Morton

Provides a bird’s eye view of North America’s most gorgeous and spectacular geological formations, from the Great Salt Lake in Utah to the Chicxulub Crater in Mexico, along with information on each site’s formation and what makes each one noteworthy.
Reading the rocks : the autobiography of the earth
by Marcia Bjornerud

This armchair guide to the making of the geologic record shows how to understand messages written in stone. To many of us, the Earth's crust is a relic of ancient, unknowable history--but to a geologist, stones are richly illustrated narratives, telling gothic tales of cataclysm and reincarnation. For more than four billion years, in beach sand, granite, and garnet schists, the planet has kept a rich and idiosyncratic journal of its past. Fulbright Scholar Bjornerud takes the reader along on an eye-opening tour of Deep Time, explaining what we see and feel beneath our feet. Both scientist and storyteller, Bjornerud uses anecdotes and metaphors to remind us that our home is a living thing with lessons to teach. She shows how our planet has long maintaineda delicate balance, and how the global give-and-take has sustained life on Earth through numerous upheavals.--From publisher description
Roadside geology of Texas
by Darwin Spearing

The geologic panorama of Texas is as wide as the state is big, sweeping from volcanic mesas and thrusting mountains in the west to red canyons of the Panhandle, along tropical sand barriers of the Gulf Coast, and across central limestone plateaus onto hard granitic terrain in the center of the state. Texas is bless with rocks of all ages, as well as an incredible array of natural geologic resources. Darwin Spearing will tell you about the rocks as you come to them--describing what they are, when they formed, what they mean, and how they fit into the big picture of the geology of Texas. -From the publisher description
Sedimentary Structures
by John Collinson

 Since its first publication in 1982, Sedimentary Structures has established and maintained itself as a pre-eminent resource that sets out a clear methodology and philosophy for understanding present-day sediments and sedimentary rocks as the product of dynamic processes.
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