Trailback 2 Lodève
« A winters day, in a deep and dark December…” Paul Simon.
Whilst driving through France in a diagonal north to south work-rush, I deviated toward the sparse badlands of the Lodève region; left the beaten track, and headed toward the Lieude rock formation, finally finding the place after a seemingly endless route through astonishing sandy red mountainous landscapes.
On that dark day, cold lingering mists of a miserable December hung motionless at low altitude, in what is normally a sun drenched sedimentary hell, even at this time of year. It is here, within the vicinity of the strata, that 20 individual fossil trails appear upon a red mudstone mega-track-site which is over 220 metres long.
This big-fossil is altogether strewn with thousands of prints. Paleontologist G. Gand examined this context several years ago, before describing the ichnospecies of suspected mammal-like-reptilian therapsids, such as Lunaepes ollierorum and Merifontichnus thalerius (a possible dicynodont), and therosaurs such as Brontopus circargiganteus, a probable large caseid dinocephalian measuring 5 metres in length.
The numerous fossils upon the sloping floor at Lieude formation are sadly scarcely visible, for the site is enclosed by high metal fencing as if Top Secret territory. On this dull day, it is hard to imagine that this remnant was once a shallow channel-bank waterhole attraction to a mix of primitive reptiles and amphibians of the wind blown barren desert, stretching through 260 million years of deep time gone.
I searched the rocks surrounding the ugly fencing, and found wind driven ripple mark trace fossils throughout the area. This site has potential for further excavation, and must surely hide many more ancient footprints.
For this rare stone, which has for 20 years now been protected simply as a kind of in-situ-prohibition, there is a future museum project; let’s hope they get it right.
Elsewhere, somewhere bordering the blood-red Salagou river, on-going paleontological digs resume this coming summer; the fossil remains of a tupilakosaurid amphibian and a mammalian-type-reptile of gorgonopsid morphology have been discovered, and are perhaps slightly older than the Lieude context. Both vestiges here are dated within the Permian, Saxonian times.
The richest fossil inferences from this strange, isolated area derive from within the mid-Permian stage of the Saxonian (which span the World-wide Permian scale of the Upper Cisuralian, and Lower Lopingian). There are 2 main geological formations concerning this specific time at Lodève; Salagou-Lieude on one hand, and the slightly older Rabejac beds on the other.
This geographically wide-ranging red mudstone assembly contains mostly masses of ripple mark fossils, dry desiccation cracks, and yet more remarkable footprint fossils, from which further ichnotypes are recognised, including Limnopus zeilleri a possible eryopsid predator, and the reptilian amniots, Hyloidichnus, a cotylosaur, as well as Varanopus rigidus. These footprint traces also occur within other Carbo-Permian sequences, such as the Canadian Joggins Formation for example.
Throughout the entire Lodèvian rock chapter, multi-stage climate changes originating from the final Carboniferous periods towards hotter, arid Permian climes are indicated. Landscapes became progressively more arid throughout the whole northern Pangean supercontinent during this span, with maximum warmth occurring during that Saxonian mid-Permian, and thus near a time referred to as Olsen’s gap.
Olsen’s gap may have been a small-extinction-event. As from the 1930’s Everett Olsen (1910-1993) became a renowned paleontologist with a keen eye for Permian vertebrate fossils. He pioneered fossil statistical comparisons, and encouraged taphonomic study from in situ fossil sites.
He deciphered much of the fossil bearing Permian strata on a World-wide scale by correlating biostratigraphies, and in doing so realized that a ‘short’ time period of perhaps 2 million years was absent of fossils, throughout the globe, during these specific times of mid-Permian. The time-gap, which was initially noticed by comparing Texan and South African tetrapod-rich Permian strata, became know as ‘Olsen’s gap’, and is situated somewhere around 271 million years ago.
Later research seemed to slowly fill that Gap, but in a fascinating recent paper by S. Lucas, the Olsen’s gap is convincingly argued to persistently remain silent and inert of fossils, although it has been partially closed (not filled), with findings from Arizona, Texas and New Mexico, which are slightly younger remnants than the fossils from Lodéve’s Rabajac formation.
After the 2 million year gap, ‘new’ fossils are yielded from the Val Gardena sandstone of Italy, which correlate neatly to the fossil prints from the Lieude farm at Lodève.
During this time, certain terrestrial land creatures evolved suddenly and rapidly, such as the pig sized herbivore Lystrosaurus, but for which reason, confirms Lucas, ‘the fossil record remains to be discovered’. One day and eventually, that evidence will indeed come to light. This new, rapid evolutionary development is known as the ‘Kanzian Revolution’, after the post-Olsen’s gap fossils discovered in Russia.
Later, a few million years after the formation of the remarkable Saxonian stratigraphies, the famous Global Permian extinction episode occurred, and dates around 251 million years ago. Life was decimated at this time, with both land and marine diversity being greatly affected; certain corals for instance were wiped clean, and the trilobites vanished forever….and the great Permian extinction was the only natural catastrophe to have truly affected the insects.
Continuing the chronological ascent of the Lodève strata, I head west toward the village of Dio, to encounter mid-Triassic horizons set within the Anisian stage; thus millions of years after that great extinction.
A mix of conglomerate and sandstone at this area frequently reveal plant fossils…but the most impressive remnants, and once more typifying the fossils throughout this Basin, are the footprints left by an array of both mammal-like reptiles, as well as amphibians.
The Lodèvian-Anisian has shown for example traces of Rotodactylus sp, which some authors describe as a dinosaurian, and Chirotherium barthii, which are the reminders of a narrow tracked, medium sized thecodont. And another thecodont trail from the Triassic sediments here is that of Brachychirotherium sp, which is so exquisite that even scaly skin texture is visible upon the print. Claw marks remain present on the track of yet another Brachychirotherium passage.
Finally, both adult and juvenile prints have been found in the region from the archosaur reptile, Rhynchosauroides sp, which is a fairly common trace fossil throughout the eastern French Massif Central range. To date, no vertebrate body fossils have been recovered from this Triassic stratigraphic contexts from Lodève’s Dio, which was first examined in 1857 by the French naturalist P. Gervais.
A scientific study, undertaken by G. Gand and colleagues in 1987 has correlated the entire Permian tetrapod ichnofauna for the Basin, and together lists a total of 22 ichnospecies. They have thus corrected earlier Lodève identifications, some of which wrongly mentioned over 130 individual ichnotypes.
After the Dio and the Lieude scramble, I set off toward a nearby abandoned uranium quarry, near the Mas d’Alary hamlet. Within an hour of sifting and searching alone through discarded (Saxonian) red mudstone, most probably deriving from the Rabejac formation, I found a slab showing rain drop trace fossils, and later a superb stone containing small fossil footprints and tiny claw marks…just as those morning mountain mists converted to freezing afternoon rains; I headed for Lodève, taking shelter from winter rage in the town’s natural history museum !
From within the basin of Lodève, piles of fossil trails have been pulled into the light. Lodève is but one old page however, with its enigmatic fossil tracks skimming back and forth. The assembly helps connect the on-going chapter somewhere in the very deep time of ancient Earth Life, despite Olsen’s gap, and thus remains a treasured perspective concerning the fabulous topic we call paleontology.