BIG BEND | GeologyVirtualTrips

BIG BEND NATIONAL PARK

FIELD TRIP STOP - LARAMIDE OROGENY UPLIFT OF CRETACEOUS FOLLOWED BY TERTIARY EXTENSION WITH VOLCANISM AND BLOCK FAULTING

LOCATION: Big Bend National Park is located in West Texas near the Mexican Border. It is fairly isolated geographically, with the nearest major city being El Paso, TX about 300 miles away. The northern park entrance (Persimmon Gap) is found about 100 miles south of Fort Stockton, TX via US-385.

GEOLOGIC FEATURES: Laramide Orogeny; Ouachita (Marathon) Orogeny; Igneous Intrusive and Extrusive; Cretaceous Carbonates; Volcanic Ash, Tuff, and Lava; Rhyolite; Basin and Range: Block Faulting.

DESCRIPTION: When travelling through Big Bend National Park, you will notice that the rock types and ages that you see most prominently displayed fall mainly into two major groups – Cretaceous sedimentary (mainly limestone) rocks and Lower Tertiary Volcanic and Plutonic Igneous Rock.

The very general geologic history of the Park can be summarized as follows, with (1) being the oldest event and (8) the youngest:

(1) PALEOZOIC DEPOSITION: Deposition of Paleozoic sediments.

(2) OUACHITA MOUNTAIN BUILDING: Mountain building during the Ouachita (Marathon) Orogeny from the uppermost Mississippian to the earliest Permian (about 330 to 285 mya). (Some Paleozoic rock and evidence of this orogeny are present in the far north part of the Park near Persimmon Gap.)

(3) CRETACEOUS DEPOSITION: Erosion (or non-deposition) during the Triassic and Jurassic followed by deposition and large accumulatios of mainly Cretaceous fossiliferous carbonates and shales within a shallow seaway.

(4) LARAMIDE MOUNTAIN BUILDING: Mountain Building during the Laramide Orogeny from the Upper Cretaceous to the Lower Tertiary (70 to 50 mya) that uplifted the Cretaceous. (Massive layers of limestone can be found in the Sierra del Carmen to the east of the Park, including Boquillas Canyon, as well as the Mesa de Anguila to the west, including Santa Elena Canyon.

(5) TERTIARY DEPOSITION: Deposition of Lower Tertiary (Paleocene-Eocene) clastic sediments (63 to 55 mya) largely in the Boquillas Basin.

(6) TERTIARY VOLCANICS AND INTRUSIVES: Tertiary emplacement of Volcanics and Intrusive Igneous Rock (Eocene to Oligocene) (46 to 28 mya). (These are spectacularly displayed in the Chisos Mountains as well as the western part of the Park.)

(7) TERTIARY BLOCK FAULTING: Block Faulting in the Miocene and Pliocene (mainly between 25-10 mya) associated with the Basin and Range Province (25 to 2 mya). This event produced stretching of the area and block faulting throughout the park. (Block faulting is thought to be responsible for significant uplift of the Cretaceous Limestones in the Sierra del Carmen and Mesa de Anguila at the easternmost and westernmost parts of the Park.)

(8) EROSION: Differential erosion during the last few million years has shaped the present park surface as evidenced by the removal of huge amounts of sediment to expose intrusive igneous rock.

(9) RIO GRANDE FORMATION: Over the past 2 million years, the Rio Grande carved the spectacular Canyons (Boquillas and Santa Elena).

STUDENT QUESTIONS:

(1) Explain the process of Differential Weathering and Erosion?

(2) What is Volcanic Tuff and how does it differ from Ash?

(3) Why is Volcanic Ash commonly associated with Rhyolitic Lava?

(4) What is the cause of the Laramide Orogeny?

(5) CHALLENGE: In most textbooks Rhyolites are generally considered to be extrusive. Why, then, are they noted as "intrusive" in many geologic descriptions of Big Bend National Park?

(6) CHALLENGE: What is the cause of the Ouachita Orogeny and when did it occur?

(7) CHALLENGE: What is the cause of the Basin and Range extensional tectonics and when did it occur?

SELECTED REFERENCES:

-Harris, Ann. and Esther Tuttle. 1983 (3rd ed). Geology of National Parks. Kendall / Hunt Publishing Co., Dubuque, Iowa, 554 pp.

-Harris, David V. and Eugene P. Kiver. 1985 (4th ed.). The Geologic Story of the National Parks and Monuments. John Wiley and Sons, New York, 464 pp.

-Kempter, Kirt. Geology of Western National Parks: Big Bend, TX. Accessed on Dec. 31, 2024 from https://smithsonianassociates.org/ticketing/attachments/255769/1/pdf/Big-Bend-Handout

-Maxwell, Ross A. 1968. The Big Bend of the Rio Grande, A Guide to the Rocks, Landscape, Geologic History, and Settlers of the Area of Big Bend National Park. Bureau of Economic Geology, The University of Texas at Austin, Guidebook 7, 138 pp.

-NPS. Geology of Big Bend. Updated Dec. 22, 2020. Accessed on Dec. 31, 2024 from https://www.nps.gov/bibe/learn/nature/rocks.htm.

-NPS. Maps: Big Bend National Park Maps. Updated Oct. 31, 2023. Accessed on Dec. 31, 2024 from https://www.nps.gov/bibe/planyourvisit/maps.htm.

-Spearing, Darwin. 1991. Roadside Geology of Texas. Mountain Press Publishing Co., Missoula, Montana, 418 pp.

-Travelingeologist. Exploring the Geology of Big Bend National Park with Kellen Gunderson. Accessed on Dec. 31, 2024 from https://www.travelinggeologist.com/2017/02/exploring-the-geology-of-big-bend-national-park-with-kellen-gunderson/

-Turner, Kenzie J. 2011. Geologic Map of Big Bend National Park, Pamphlet to accompany Scientific Investigations Map 3142. USGS, Reston, Virginia, 84 pp. Accessed on Dec.31, 2024 from https://pubs.usgs.gov/sim/3142/downloads/pdf/SIM3142_pamphlet.pdf

FIGURES:

Big-Bend-National-Park-Brochure-Map (1).jpg

FIGURE A - Map of Big Bend National Park

FIGURE B - Geologic Map of Big Bend National Park showing the major rock units and structure (from USGS)

PHOTOS:

FIGURES 1-3 - PHOTOS FROM NORTH ROAD - BETWEEN PERSIMMON GAP ENTRANCE & PANTHER JUNCTION

Figure 1 - Entrance to Big Bend National Park's northern entrance at Persimmon Gap.

Figure 2 - View of the Chisos Mountains from five miles north of the Panther Junction Visitor Center. The Chisos Mountains are composed of Tertiary Igneous rock, both intrusive and extrusive.

Figure 3 - Left to Right: Pummel Peak, Wright Mountain, and Panther Peak as viewed from the Panther Junction Visitor Center. Each of these is composed of Oligocene Rhyolite that was emplaced intrusively with erosion eventually stripping away the overlying sediment.

FIGURES 4-10 - PHOTOS FROM EAST ROAD - BETWEEN PANTHER JUNCTION AND RIO GRANDE VILLAGE

Figure 4 - Nugent Mountain, an outlier of the Chisos Mountains, is an Oligocene intrusive igneous rock exposed by erosion.. The view is to the west of the road and about 10 miles south of Panther Junction.

Figure 5 - Tunnel runs through the Cretaceous Santa Elena Limestone of the Sierra del Carmen. Photo is from the Rio Grande Overlook (near Rio Grande Village).

Figure 6 - Steep walls of the Sierra del Carmon, thick deposits of Cretaceous limestone uplifted during the Laramide Orogeny and Tertiary block faulting. View is from the road between the Rio Grande Overlook and Boquillos Canyon..

Figure 7 - Lower Cretaceous limestone viewed from the Boquillas Canyon Overlook.

Figure 8 - The Lower Cretaceous Santa Elena Limestone viewed from the Boquillas Canyon Overlook. The Santa Elena Mountains were uplifted several thousand feet due to Tertiary block faulting associated with the Basin and Range Province extensional tectonics.

Figure 9 - The Tertiary igneous rock (largely Oligocene intrusives) of the Chisos Mountains viewed from the road leading northwest towards Panther Junction. Note Nugent Mountain at the right of of the photo.

Figure 10 - A closer view of the Chisos Mountains with Nugent Mountain in the central foreground

FIGURES 11-17 - PHOTOS FROM CHISOS BASIN ROAD - BETWEEN THE MAIN ROAD AND THE CHISOS BASIN

Figure 11 - Chisos Mountains. Jagged peaks surround the Basin Road.

Figure 12 - Looking northward from the Chisos Mountains to the lowlands below.

Figure 13 - Tertiary Igneous rock viewed on the road to Chisos Basin.

Figure 14 - The Chisos Basin Visitor Center. Peaks of Tertiary Intrusive Igneous rock rise about 2500 ft above the Basin floor.

Figure 15 - Looking north from the Chisos Mountain Lodge Restaurant with a view of "The Basin." This basin is the product of differential weathering with the surrounding peaks being composed of hard intrusive igneous rock. Ward Mountain is to the left. "The Window" is to the right, near the center of the photo. Immediately to the left of The Window is Carter Mountain. The Window is a gap in the mountains through which water and sediment from the surrounding slopes are funneled.

Figure 16 - Rhyolite is a common rock in The Basin.

Figure 17- Casa Grande Peak and exposures to the right are the remains of extrusive lava flows.

FIGURES 18-22 - PHOTOS FROM SOUTH ROAD (MAXWELL SCENIC DRIVE) -BETWEEN THE MAIN ROAD AND SANTA ELENA CANYON

Figure 18 - Distinctive lava flows are interbedded within tuffaceous sandstone and clay, tuff, ash beds, and conglomerates. View to to the east of the road.

Figure 19 - View of the Homer Wilson Ranch, a former sheep ranch abandoned in 1945. This is a popular hiking destination in the park.

Figure 20 - White volcanic ash and tuff look like snow cover the landscape and contrast sharply with the darker volcanic rock. Nearby Tuff Canyon exposes thick accumulations of whitish tuff and ash. Being readily soft, the tuff and ash are readily weathered and eroded.

Figure 21 - Steep walls of Lower Cretaceous sedimentary rocks in the area of Santa Elena Canyon (in the Mesa de Anguila). From top to bottom are the Santa Elena Limestone, Sue Peaks formation, and Del Carmen Limestone.

Figure 22 - Lower Cretaceous sedimentary rocks of the Mesa de Anguila near the Santa Elena Canyon.