Stunning Magic of the Salta Rift Basin

Imagine what this special land looked like 100 million years ago. The Salta Rift Basin reveals many wonders, and on your adventure with Travel Vision Journeys, you’ll learn about them from a unique and timeless perspective.

The Salta Rift Basin is a high plateau region including the province’s capital city of Salta and the towns of Cafayate and Cachi. Your itinerary leads you through gorgeous vistas, amazing rock formations, and magnificent views of the Andes. Each perspective tells a different story of geologic time and ancient natural history.

This area is geologically significant for its various epochs of rock-altering events. Oozing magma, rifting breaks of the Earth’s crust, inland seas and sediments, climate change, and plate and inversion tectonics played starring roles in creating the fascinating landscape you see today. Complicating matters, these events happened not one after the other, but in a mix of cataclysms over hundreds of millions of years and continuing today.

What’s the geological big picture?

Argentina sits on the South American Plate, a region of the Earth’s crust extending from the shores of the Pacific Ocean to the middle of the Atlantic. It was once part of a supercontinent containing modern South America and Africa. Examine the offsetting coasts today and you’ll see they fit together closely like pieces of a prehistoric puzzle.

In the center of the Atlantic, the Mid-Atlantic Ridge formed when the supercontinent separated. It still widens today, adding new lithosphere (crust) far below the water’s surface. The South American Plate has been riding west on a conveyor belt of magma for millions of years, all the while cracking in rifts, pulling apart in blocks, and slamming its pieces back together.

The Nazca Plate, the floor of the Pacific Ocean, dives underneath the South American Plate, melting as it goes and causing the string of active volcanoes near the western edge of the continent. The present-day Andes were once part of flat plain, but the constant push of plate against plate buckled them into their towering heights. It’s amazing what a little plate tectonics will do!

South America is still moving west at the astounding (in geological terms) rate of three inches (77 mm) a year. Compared to the movements of other plates around the globe, this is a gold medal winner! While the human eye will only capture major changes through cataclysmic events like earthquakes or volcanic explosions, nature continues to alter this region in big ways evidenced in the rock formations we see today.

Where did these rocks come from?

It’s impossible to escape noticing the layering in rocks around the region. These formed as sediment under varying types of water. Research shows that as the continent shifted, stretched and compressed, large blocks of crust dropped into voids or thrust up when squeezed.

When land fell below sea level, the ocean rushed in. Periods of high water also occurred during global climate warming. Other major events like earthquakes, plates moving in a sudden jerking motion, tsunamis, seasonal wave patterns, and long-term storm surges also changed the composition of these inland seas.

Sediment settled in areas where crust blocks subsided, filling in and leveling the sea floor. Areas then lifted, twisting the rock. When it was exposed above water for thousands of years, soil formed, plants grew, and creatures roamed. These formed another layer when the inland sea again inundated the continent.

Imagine this happening hundreds of times with varying climates, each creating striking differences in the segments of rock. Sandstone, mudstone, marine slates, and carbonates interspersed with at least three major volcanic events, coating the continent with magma cooling into yet another profoundly different layer of granite or basalt. When layers were squeezed in high temperatures and pressures, metamorphic rocks like quartzites were added to the structure.

How old are these rocks?

Scientific estimates mark the beginning of the sedimentary layers as the Early Cretaceous period in the geologic time scale, approximately 145 million years ago to about 80 million years ago. Dinosaurs were still around but their distribution and species were changing, giving rise to new reptiles and amphibians. Deposits became increasingly alkaline (salty) as time went on, leaving behind distinctive salt flats you see today in places like Las Salinas Grandes.

Researchers believe the sedimentary rock extends about 16,000 feet (5,000 meters) down – that’s three miles! The weight of these rocks depresses the crust, creating some of the thickest lithosphere on the planet.

Even this, though, is no match for the rifting and squeezing of plate-on-plate action, lifting the twists and turns of layers until they are inverted, oldest on top of youngest. Your fingers may be touching rock that formed at the bottom of a salty riverbank 100 million years ago.

What caused the colors in layers?

The chemical composition of the water, creatures and vegetation produced the colorations we see today. In the period when these sediments began settling, the climate was generally warm, and high sea levels brought an influx of a large, shallow inland sea covering modern day Argentina and Chile. An active period for volcanoes released ash and carbon dioxide into the atmosphere, further warming temperatures and adding another geologic layer.

 

Exposure to conditions in modern time add greater complexity to what you see today. Interactions with what the atmosphere and rain carry in terms of gasses, particulates and chemicals can alter colors. Even the direction of prevailing winds plays a role in how layers change when they are exposed.

Canyons, valleys, ravines and mountains like La Quebrada de as Flechas, Valle Encantado, and Paseo de Los Colorados each offer different perspectives of coloration, formation, and geologic time. Some of this is relatively modern, younger than twenty million years ago. The layers continue to build to this day, with each successive epoch of water and rock introducing its own unique characteristics into the geologic record.

And in another million years?

It’s easy to get lost in the colors, or the layers, or the vistas. As you search the horizons, though, don’t forget the small details in front of you. A layer of rock may offer the impression of an ancient leaf. The pattern of sediment can tell you how it was formed when compared to alternatives you’re familiar with.

Remember that warp-speed of this continent’s present-day movement. Changes in this region haven’t ended. What do you think it will look like in another million years?

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