March 2017 
StratoChem Goes to AAPG ACE 2017


We're pleased to announce that the whole StratoChem North America team will be in Houston at the end of March and beginning of April for the American Association of Petroleum Geologists' Annual Convention and Exhibition.  Exhibitions like ACE are good ways to take the temperature of the industry, and just as the weather thaws and spring begins, so too do we look forward to seeing a rejuvenating, vital industry as we emerge from the downturn.  If you're going to ACE, we would love to catch up.  We'll be circulating on the floor, meeting up with old friends and making new ones.  We hope you'll come join us!

Sasol announces Mozambique oil find
Wadi Al Hitan:
Whales in the Desert

Even Herman Melville's Moby Dick, one of the most famous whale stories of all time, makes the mistake: the narrator Ishmael clearly refers to whales as "fish."  While Melville probably knew whales were mammals rather than fish, the word choice is glaring.  But even if we recognize that whales (being warm-blooded air-breathers that nurse their young) are in fact mammals rather than fish, the question remains: how did they come to live exclusively in the water-and particularly in deep marine environments inhospitable to normally land-dwelling mammals?  Some unexpected answers to this unique evolutionary riddle can be found, of all places, deep in the Egyptian Sahara.


Wadi Al'Hitan ( وادي الحيتان or "Valley of the Whales"), a paleontological site in the Fayoum Governorate of Egypt, 150 kilometers southwest of Cairo, forms a part of the nature reserve at Wadi Al'Rayan, already home to some of Egypt's most famous archeological sites. The dry and relatively unchanging nature of the desert creates conditions optimal for preservation not only of traces of human settlement, but the remains of ancient animals as well. The valley boasts fossils of many ancient aquatic species, and, true to its name, some of the most impressively preserved ancient whales (archaeocetes) found anywhere in the world.
While the fossils at Wadi Al'Hitan are by no means the oldest (the true ancestral whale, a four-legged carnivore called Pakicetus, was discovered in Pakistan's Kuldana Formation), no other site in the world possesses such a comprehensive and well-preserved collection of ancient whale remains.
The Pakicetus, four-legged ancestor to the modern whale

The discovery of whale fossils in the Fayoum area began in 1902 with seven species. Early paleontologists saw the serpentine shapes and sharp teeth of these whales and named the genus Basilosaurus ("king lizard"), believing them to be reptiles. Upon closer examination, it became clear that the basilosaurids were actually whales. Famed paleontologist Richard Owen lobbied to have the Basilosaurus genus name changed to Zeuglodon ("yoke tooth," after the shape of its dentition), but with only mixed results. Paleontologists today use both names interchangeably.  Whatever their collective name, the basilosaurid fossils began to reveal a world very different from the arid Sahara in which scientists first discovered their fossils.
Skull of the Basilosaurus whale displayed at Wadi Al'Hitan

The Tethys Sea
 
About 50 million years ago, the Egyptian Sahara formed part of the bottom of the Tethys Sea, a body of water lying between the continents of Gondwana and Laurasia during the Mesozoic Era before the opening of the Atlantic and Indian Oceans. To understand the world of the basilosaurids, one must be able to understand the geological conditions that created their world.
 
Today's Wadi Al'Hitan is defined by the cliffs and buttes created by wind and water erosion-a direct result of the sediments deposited over 40 million years ago by the Tethys Sea: the sandstone, shale and limestone visible in the three main rock formations of the valley. The oldest rocks, part of the Eocene Gehannam Formation, are comprised principally of limestone and clay and bear the skeletal remains of whales and sirenians (the order containing dugongs and manatees), as well as turtles and crocodilians. Rocks belonging to the Gehannam Formation are mostly visible on the flatter grounds of the valley. The Birket Qarun Formation forms the Middle Eocene and younger layer that yields the richest deposits of whale fossils. It consists of yellowish open marine sandstones that form most of the cliffs and buttes in addition to a white layer full of well-preserved animal burrows. The youngest formation, the Qasr El Sagha at 39 million years old, is rich in marine invertebrate indicative of a shallow marine environment. Rocks belonging to this formation are dark mudstones and limestones found atop the higher cliffs, representing a lagoonal environment.  It was in these shallow waters that the basilosaurids dwelt.

Rock formation at Wadi Al'Hitan

The World of Basilosaurus
 
The collection of aquatic species preserved in Wadi Al'Hitan testifies to the rich shallow sea that once covered the area, providing a fertile world to house the basilosaurids-but what were they like?
 
They looked very different from modern whales.  Basilosaurus isis, one of the largest whales discovered in Wadi Al'Hitan was almost certainly the top carnivore of its corner of the Tethys.  With a snakelike shape and sharp teeth honed by evolution to crack bone, Basilosaurus was an apex predator whose bite-force rivaled that of the carnivorous dinosaurs that had gone extinct 30 million years before.  At sizes of up to 50 feet in length, it preyed on other whales--including smaller basilosaurids like the porpoise-like Dorudon atrox (also found at Wadi Al'Hitan)-as well as fish and crustaceans.  Given the number of young basilosaurids discovered in Wadi Al'Hitan, it seems likely that the whales migrated there to give birth.
A pod of basilosaurid whales. Image by Pavel Riha.

But for all its impressive ferocity, one of the most important parts of Basilosaurus, at least for those trying to piece together the greater story of whales, is one of the most seemingly insignificant: its hind legs. 
 
The fossil record reveals it took around 10 million years for whales to evolve from being fully terrestrial mammals to fully aquatic ones. The archaeocetes at Wadi Al'Hitan are now extinct, but they were ancestors to modern cetaceans-whales, dolphins, porpoises, etc. Modern cetaceans retain a "phantom" hip bone found in modern-day whales and dolphins, where the legs once attached to the body. In archaeocetes like the basilosaurids, this bone retains small flippers.  Clearly, the basilosaurids were in the final stage of losing their hind limbs and beginning to take on the body-shape of modern whales. Such a transition would allow their migration from the shallow coastal waters where the basilosaurids lived into open oceans. 

Ongoing Discoveries
 
To prevent looting by tourists, UNESCO declared Wadi Al'Hitan a World Heritage Site in 2005.  As recently as 2015, the Egyptian National Task Force paleontological field team discovered a new deposit of remains, including a complete specimen of Basilosaurus isis approximately 40 million years old. The team also discovered fossilized remains of sea creatures inside what would have been the whale's stomach, identifying fragments of crab, sawfish and a small whale and giving invaluable insight into the diet of these missing links.  Protected under international law and investigated by teams of trained paleontologists, it's certain that we haven't seen the last of Wadi Al'Hitan's secrets.













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