#Causses Basin

[sciencenewsforstudents]

Crawling through tight underground passages in southern France, paleontologist Jean-David Moreau and his colleagues have to descend 500 meters below the surface to reach the only known footprints of long-necked dinosaurs called sauropods ever found in a natural cave.

The team discovered the prints, left by behemoths related to Brachiosaurus, in Castelbouc Cave in December 2015 (SN: 2/21/18). But getting to the site might make even the most hardened field scientists balk. Wriggling through such dark, damp and cramped spaces every time they visit is challenging for elbows and knees, and even trickier when carrying delicate equipment such as cameras, lights and laser scanners.

It’s both physically exhausting and “not comfortable for someone claustrophobic,” with the researchers spending up to 12 hours underground each time, says Moreau, of the Université Bourgogne Franche-Comté in Dijon. It can be dangerous too, as some parts of the cave are periodically flooded, so accessing the deep chambers must be limited to periods of drought, he says.

Moreau has studied fossilized dinosaur footprints and plants for more than a decade in southern France’s Causses Basin, one of the richest areas for aboveground dinosaur tracks in Europe. When spelunkers chanced upon some underground prints in 2013, Moreau and his colleagues realized there could be lots of dinosaur prints within the region’s many deep, limestone caves. Footprints left in soft mud or sand hundred million years ago could have been turned to rock and forced underground over many eons.

And deep caves, being less exposed to wind and rain, “can occasionally offer larger and better-preserved surfaces [imprinted by dinosaur steps] than outdoor outcrops,” Moreau says.

Moreau’s team is the only one to have discovered dinosaur footprints in natural caverns, though prints also have been found around the world in human-made railway tunnels and mines. “The discovery of dinosaur tracks inside a natural karstic cave is extremely rare,” he says.

The first subsurface dinosaur prints that the team found were 20 kilometers away from Castelbouc at a site called Malaval Cave, reached via an hour-long clamber through an underground river with several 10-meter drops. “One of the main difficulties in the Malaval Cave is to walk taking care to not touch or break any of the delicate and unique [mineral formations],” Moreau says.

Those three-toed prints, each up to 30 centimeters long and detailed in 2018 in the International Journal of Speleology, were left by carnivorous dinosaurs walking upright on their hind legs through marshland about 200 million years ago.

[liliannorman]

The challenge of dinosaur hunting in deep caves

Being a paleontologist can be fun. Sometimes it also can be a bit scary. Like when you’re crawling through tight underground passages in a deep, dark cave. Yet that’s what Jean-David Moreau and his colleagues have chosen to do in southern France. For them, the payoff has been rich. For instance, after descending 500 meters (a third of a mile) below the surface at one site, they discovered footprints of enormous, long-necked dinosaurs. They’re the only such sauropod footprints to ever turn up in a natural cave.

Moreau works at the Université Bourgogne Franche-Comté. It’s in Dijon, France. While at Castelbouc Cave in December 2015, his team found the sauropod prints. They had been left by behemoths related to Brachiosaurus. Such dinos could be almost 25 meters (82 feet) long. Some likely tipped the scales at nearly 80 metric tons (88 U.S. short tons).

Explainer: How a fossil forms

Getting to the fossil site might make even the most hardened field scientists balk. They had to wriggle through dark, damp and cramped spaces every time they visited. That’s exhausting. It also proved hard on their elbows and knees. Carrying along delicate cameras, lights and laser scanners made it extra tricky.

Moreau also points out that it’s “not comfortable for someone claustrophobic” (afraid of tight spaces). His team spends up to 12 hours each time it ventures into these deep caves.

Such sites also can pose real danger. For instance, some parts of a cave flood now and again. So the team only enters the deep chambers during periods of drought.

Moreau has studied dinosaur footprints and plants in southern France’s Causses Basin for more than a decade. It is one of the richest areas for aboveground dinosaur tracks in Europe.

Cave explorers, known as spelunkers, first chanced upon some underground dino tracks in 2013. When Moreau and his colleagues heard about them, they realized there could be lots more hidden throughout the region’s deep, limestone caves. Footprints left in soft surface mud or sand a hundred million years ago would have turned to rock. Over the eons, these would have been forced underground.

Compared to outdoor rocks, deep caves are exposed to little wind or rain. That means they “can occasionally offer larger and better-preserved surfaces [imprinted by dinosaur steps],” Moreau observes.

His team is the only one to have discovered dino tracks in natural caverns, although others have turned up similar prints in human-made railway tunnels and mines. “The discovery of dinosaur tracks inside a natural … cave is extremely rare,” he says.

Paleontologist Jean-David Moreau examines a three-toed footprint in Malaval Cave in southern France. It was left by a meat-eating dinosaur millions of years ago.Vincent Trincal

What they’ve turned up

The first subsurface dinosaur prints that the team found were 20 kilometers (12.4 miles) away from Castelbouc. This was at a site called Malaval Cave. The paleontologists reached it via an hour-long clamber through an underground river. Along the way, they encountered several 10-meter (33 foot) drops. “One of the main difficulties in the Malaval Cave is to walk taking care to not touch or break any of the delicate and unique [mineral formations],” Moreau says.

They found three-toed prints, each up to 30 centimeters (12 inches) long. These came from meat-eating dinosaurs. Some 200 million years ago, the animals left the tracks while walking upright on hind legs through a marshland. Moreau’s team described the prints in early 2018 in the International Journal of Speleology. 

Explainer: Understanding geologic time

They also found tracks left by five-toed plant-eating dinos in Castelbouc Cave. Each footprint was up to 1.25 meters (4.1 feet) long. A trio of these enormous sauropods had been walking along the shores of some sea roughly 168 million years ago. Especially interesting are prints found on the cave’s ceiling. They are 10 meters above the floor! Moreau’s group shared what they found online March 25 in the Journal of Vertebrate Paleontology.

“The tracks we see on the roof are not ‘footprints,’” Moreau notes. “They are ‘counterprints.’” He explains that the dinos had been walking on a surface of clay. The clay beneath those prints “is nowadays totally eroded to form the cave. Here, we only see the overlying layer [of sediment that filled in the footprints].” These amount to reverse prints bulging down from the ceiling. It’s similar, he explains, to what you’d see if you filled a footprint in mud with plaster and then washed all of the mud away to leave the cast.

The tracks are important. They hail from a time in the early- to mid-Jurassic Period. This would have been 200 million to 168 million years ago. At that time, sauropods were diversifying and spreading across the world. Relatively few fossil bones from that time remain. These cave prints now confirm that sauropods had inhabited coastal or wetland environments in what is now southern France.

Moreau reports that he is now leading researchers in exploring “another deep and long cave, which has yielded hundreds of dinosaur footprints.” That team has yet to publish its results. But Moreau teases that they may prove to be the most exciting of all.

The challenge of dinosaur hunting in deep caves published first on https://triviaqaweb.tumblr.com/

[frankkjonestx]

Deep caves are a rich source of dinosaur prints for this paleontologist

Crawling through tight underground passages in southern France, paleontologist Jean-David Moreau and his colleagues have to descend 500 meters below the surface to reach the only known footprints of long-necked dinosaurs called sauropods ever found in a natural cave.

The team discovered the prints, left by behemoths related to Brachiosaurus, in Castelbouc Cave in December 2015 (SN: 2/21/18). But getting to the site might make even the most hardened field scientists balk. Wriggling through such dark, damp and cramped spaces every time they visit is challenging for elbows and knees, and even trickier when carrying delicate equipment such as cameras, lights and laser scanners.

It’s both physically exhausting and “not comfortable for someone claustrophobic,” with the researchers spending up to 12 hours underground each time, says Moreau, of the Université Bourgogne Franche-Comté in Dijon. It can be dangerous too, as some parts of the cave are periodically flooded, so accessing the deep chambers must be limited to periods of drought, he says.

Moreau has studied fossilized dinosaur footprints and plants for more than a decade in southern France’s Causses Basin, one of the richest areas for aboveground dinosaur tracks in Europe. When spelunkers chanced upon some underground prints in 2013, Moreau and his colleagues realized there could be lots of dinosaur prints within the region’s many deep, limestone caves. Footprints left in soft mud or sand hundred million years ago could have been turned to rock and forced underground over many eons.

And deep caves, being less exposed to wind and rain, “can occasionally offer larger and better-preserved surfaces [imprinted by dinosaur steps] than outdoor outcrops,” Moreau says.

Moreau’s team is the only one to have discovered dinosaur footprints in natural caverns, though prints also have been found around the world in human-made railway tunnels and mines. “The discovery of dinosaur tracks inside a natural karstic cave is extremely rare,” he says.

The first subsurface dinosaur prints that the team found were 20 kilometers away from Castelbouc at a site called Malaval Cave, reached via an hour-long clamber through an underground river with several 10-meter drops. “One of the main difficulties in the Malaval Cave is to walk taking care to not touch or break any of the delicate and unique [mineral formations],” Moreau says.

Those three-toed prints, each up to 30 centimeters long and detailed in 2018 in the International Journal of Speleology, were left by carnivorous dinosaurs walking upright on their hind legs through marshland about 200 million years ago.

Paleontologist Jean-David Moreau examines a three-toed footprint left behind by a carnivorous dinosaur millions of years ago and now found in Malaval Cave in southern France.Vincent Trincal

In contrast, the five-toed herbivore tracks in Castelbouc Cave are each up to 1.25 meters long and were left by three enormous herbivorous sauropods that walked the shoreline of a sea about 168 million years ago. What’s more, these prints are on the cave’s ceiling 10 meters above the floor, the team reports in a study published online March 25 in Journal of Vertebrate Paleontology.

In fact, “the tracks we see on the roof are not ‘footprints,’ they are ‘counterprints,’” Moreau explains. “The dinosaurs walked on a surface of clay, which is nowadays totally eroded to form the cave. Here, we only see the overlying layer [of sediment that filled in the footprints],” leaving reverse prints bulging out of the ceiling. It’s similar to what you’d see if you filled a footprint in mud with plaster and then washed all of the mud away to leave the cast.

The tracks are important as they hail from a time in the early to mid-Jurassic Period from 200 million to 168 million years ago when sauropods were diversifying and spreading across the world, but relatively few fossil bones have been found (SN: 12/1/15). These prints confirm that sauropods then inhabited coastal or wetland environments in what is now southern France.

Moreau is now leading researchers in exploring “another deep and long cave, which has yielded hundreds of dinosaur footprints,” he says. The team has yet to publish those results, which he says may prove to be the most exciting of all.

from Tips By Frank https://www.sciencenews.org/article/caves-france-dinosaur-prints-paleontology

[scienceblogtumbler]

Dinosaur Footprints on a Cave Ceiling

The footprints of sauropods, thirty-metre-long herbivorous dinosaurs, have been found on the roof of a cave located beneath the Causse Méjean plateau, in southeastern France. CNRS News talked to the palaeontologist Jean-David Moreau, who has published an article about this astonishing discovery.

One day in December 2015, a goup of amateur potholers entered the Castelbouc cave, in the Lozère department in southeastern France, for what turned out to be no ordinary outing. For inside the cavern, which is very popular with novice cavers and only accessible via a long, narrow passage, they came across a treasure trove that had remained unobserved for millions of years: the tracks of huge dinosaurs, clearly visible on the roof of the “great tunnel”, a chamber 80 metres long, 20 metres wide and 10 metres high.

“What’s so incredible is that thousands of people have passed through this cave without ever seeing a thing,” says a still dumbfounded Jean-David Moreau, a palaeontologist at the Biogeosciences Laboratory in Dijon (northeastern France) who, as head of the Lozère Palaeontology Association, organised the potholers’ outing that day. “All it took was for one person to take a closer look than usual at the ceiling, and there they were, clearly visible: the tracks of footprints apparently made by giant dinosaurs.”

Identifying them with the light from their headlamps alone was no easy task, and Moreau and his team had to return several times to confirm their amazing find: three twenty-metre-long trails left by sauropods, four-legged herbivorous dinosaurs from the Middle Jurassic, 170 million years ago. “In two of the trackways, you can see alternate foot- and handprints, the hands being identified by their half-moon shape. Some of the footprints show five toes as well as claws,” the scientist explains. “The largest are 1.25 metres in length, making them among the biggest ever identified worldwide, and were made by animals that must have measured around 30 metres.”

The discovery is unprecedented in more ways than one. To begin with, giant dinosaur prints had never been previously discovered in a cave anywhere in the world. But it is also the first time that sauropod footprints have been found in the Causses basin, even though palaeontologists have already uncovered a wealth of trace fossils there. The region, with an area of several hundred square kilometres and straddling the departments of the Aveyron, Lozère, Gard and Hérault, boasts dozens of trace fossil sites. However, no vestige of the giant herbivores had ever been spotted until now.

“The Causses basin, also called the Causses gulf, recorded the entire geological history of the Jurassic, which lasted for 55 million years,” says Moreau, who is a specialist in ichnology, the branch of palaeontology concerned with the study of trace fossils. “During this period, the sea retreated three times from the region, enabling dinosaurs to settle there: 200 million years ago, 168 million years ago – when the Castelbouc tracks are dated – and 145 million years ago.” Sediments accumulated over time, and geological layer after layer was laid down. Millions of years after the dinosaurs lived there, water infiltrated the limestones and clays of this karst environment, eventually forming the hundreds of natural cavities found in the Causses. Which explains why dinosaur tracks can be seen on the roof of a cave, which at first might appear somewhat counter-intuitive!

“There hasn’t been any upheaval in the geological strata. The trails that we see are actually casts, corresponding to the base of the sauropods’ feet,” Moreau explains. “It’s as if you were looking at the tracks left by the dinosaurs from below. What happened is that infiltrated water eroded the rock beneath the sedimentary layer which contains the footprints.”

Finding footprints on the roof might seem counter-intuitive… but can be easily explained in these caves hollowed out in limestone.

The palaeontologist, who specialises in plant fossils as well as trace fossils, was able to reconstruct the ecosystem in which the sauropods lived 170 million years ago. “We found plants, in particular remains of conifers, and small remnants of saltwater fish. An analysis of the sediments carried out in the cave told us that it was at the land-sea interface, probably on the edge of a lagoon surrounded by conifers.”

The excitement generated by the discovery has nurtured the researcher’s passion for the geologically rich region of the Grands Causses, where he hopes to find more traces of the sauropods’ presence.   “As well as continuing to explore the surfaces and outcrops where footprints are traditionally found, we’ll now be taking a very close look at the roofs of the abundant natural cavities in the area,” says Moreau, who has already started to encourage the region’s potholers to be on the lookout for fresh evidence.

source https://scienceblog.com/516341/dinosaur-footprints-on-a-cave-ceiling/

[sciencenewsforstudents]

Being a paleontologist can be fun. Sometimes it also can be a bit scary. Like when you’re crawling through tight underground passages in a deep, dark cave. Yet that’s what Jean-David Moreau and his colleagues have chosen to do in southern France. For them, the payoff has been rich. For instance, after descending 500 meters (a third of a mile) below the surface at one site, they discovered footprints of enormous, long-necked dinosaurs. They’re the only such sauropod footprints to ever turn up in a natural cave.

Moreau works at the Université Bourgogne Franche-Comté. It’s in Dijon, France. While at Castelbouc Cave in December 2015, his team found the sauropod prints. They had been left by behemoths related to Brachiosaurus. Such dinos could be almost 25 meters (82 feet) long. Some likely tipped the scales at nearly 80 metric tons (88 U.S. short tons).

Explainer: How a fossil forms

Getting to the fossil site might make even the most hardened field scientists balk. They had to wriggle through dark, damp and cramped spaces every time they visited. That’s exhausting. It also proved hard on their elbows and knees. Carrying along delicate cameras, lights and laser scanners made it extra tricky.

Moreau also points out that it’s “not comfortable for someone claustrophobic” (afraid of tight spaces). His team spends up to 12 hours each time it ventures into these deep caves.

Such sites also can pose real danger. For instance, some parts of a cave flood now and again. So the team only enters the deep chambers during periods of drought.

Moreau has studied dinosaur footprints and plants in southern France’s Causses Basin for more than a decade. It is one of the richest areas for aboveground dinosaur tracks in Europe.

[sciencenewsforstudents]

Being a paleontologist can be fun. Sometimes it also can be a bit scary. Like when you’re crawling through tight underground passages in a deep, dark cave. Yet that’s what Jean-David Moreau and his colleagues have chosen to do in southern France. For them, the payoff has been rich. For instance, after descending 500 meters (a third of a mile) below the surface at one site, they discovered footprints of enormous, long-necked dinosaurs. They’re the only such sauropod footprints to ever turn up in a natural cave.

Moreau works at the Université Bourgogne Franche-Comté. It’s in Dijon, France. While at Castelbouc Cave in December 2015, his team found the sauropod prints. They had been left by behemoths related to Brachiosaurus. Such dinos could be almost 25 meters (82 feet) long. Some likely tipped the scales at nearly 80 metric tons (88 U.S. short tons).

Explainer: How a fossil forms

Getting to the fossil site might make even the most hardened field scientists balk. They had to wriggle through dark, damp and cramped spaces every time they visited. That’s exhausting. It also proved hard on their elbows and knees. Carrying along delicate cameras, lights and laser scanners made it extra tricky.

Moreau also points out that it’s “not comfortable for someone claustrophobic” (afraid of tight spaces). His team spends up to 12 hours each time it ventures into these deep caves.

Such sites also can pose real danger. For instance, some parts of a cave flood now and again. So the team only enters the deep chambers during periods of drought.

Moreau has studied dinosaur footprints and plants in southern France’s Causses Basin for more than a decade. It is one of the richest areas for aboveground dinosaur tracks in Europe.