A slim, greenish brown band in a layer of clay clearly separates two key geologic eras all over the world, showing abnormally high microscopic concentrations of iridium, a rare dense, brittle element that best resists corrosion and bears a beautiful silvery burnish. It is prevalent in space rocks, like the six-mile wide object that slammed into the Yucatan about 66 million years ago, near the present day Mayan town of Chicxulub and cataclysmically changed life and Earth forever.
Discovered by chance in 1978, the crater emerged while the Mexican state-owned giant Pemex was meticulously mapping and searching the Gulf of Mexico for the best spots to strike oil. 
Popularly believed to be an asteroid rather than an icy comet, the violent impact literally shook the planet and left the telltale stripe that is now known as the K-Pg Boundary, formerly the K.T, separating the Cretaceous (K) and Paleogene (Pg) periods.
Widely accepted as the theory for the worldwide climate disruption and ensuing mass extinction event, in which 75% of the Earth’s plant and animal species died, including all non-avian dinosaurs, the shaded line marks their sudden extinction that consolidated the ascent of mammals and ultimately resulted in the evolution of modern humans.
The Upper Cretaceous, when it happened, is the second geological epoch in the Cretaceous, the last and longest of the three-segment Mesozoic Era. The famous Jurassic portion, 180 million to 140 million years ago was the perfect period for oil formation like the Cretaceous, 140 million to 66 million years ago.
Crude oil, a non-renewable “fossil fuel,” is so-called because it develops from the decomposing mostly planktonic remains of animals and plants that fell to the bottom of the sea or various bodies of brackish water. These end up repeatedly covered by mud and layers of sediment, causing them to change as the temperature and pressure rose, in the absence of oxygen. Eventually over time the levels morph into a dark, waxy substance, whose molecules crack, breaking up into shorter and lighter versions composed almost solely of carbon and hydrogen atoms. Depending on how liquid or gaseous this mixture is, it will eventually transform into either petroleum or natural gas.
Petroleum, literally translated as “rock oil” from the Latin petra, “rock” or “stone,” and oleum, “oil”, was first used as a word in 1546, in De Natura Fossilium, a landmark treatise published by the German mineralogist Georg Bauer also known as Georgius Agricola.
Ironically, the viable and valuable amounts of oil-bearing sandstone found recently in Guyana by the United States (US) multinational ExxonMobil Corporation and its lucky partners, are likely due to the ancient geologic, biological and climatic late Cretaceous shifts prompted by the Chicxulub collision. Just a week ago, ExxonMobil affiliate Esso Exploration and Production Guyana Limited (EEPGL), confirmed news of further high quality aged reservoirs at its Payara well, drilled 18,000 feet in 6,600 feet of water but kept details of the expected output secret.
The lucrative nearby Liza field has a prospective resource estimated in excess of 1 billion oil-equivalent barrels, located in the rich Stabroek Block, covering 6.6 million acres. Early rough estimates of how much recoverable oil Guyana possesses could run above four billion barrels at current prices topping US$200B from about 20 likely fields offshore, less than a handful of which have been checked.
ExxonMobil’s EEPGL is the operator and holds 45 percent interest in the Stabroek Block, while another US firm, Hess Guyana Exploration Ltd, has 30 percent interest and the Chinese business, CNOOC Nexen Petroleum Guyana Limited, enjoys 25 percent.
According to the 2012 World Petroleum Resources Project undertaken by the US Geological Survey, the assessed provinces of the region including South America and the Caribbean have a mean estimate of 126B barrels of oil in offshore subsalt reservoirs. The Guyana−Suriname Basin is considered to be at least 12B barrels.
In the early Cretaceous, the continents were in different positions from today. Sections of the supercontinent Pangaea were drifting apart but the North and South Atlantic were still closed, although the Central Atlantic had begun to open up in the late Jurassic Period. By the end, the continents were much closer to modern configuration with Africa and South America separating and assuming their distinctive shapes; even as India had not yet collided with Asia, and Australia was still part of Antarctica.
A mere 38 years ago, Pemex personnel were high up in a plane, oblivious to the killer Chicxulub crater, carefully measuring the magnetic field of rocks far below the sea bed, painstakingly going back and forth for weeks to study the composition of the formations and scout possible commercial drilling locations.
Combing through the reams of paper, one sharp-eyed geophysicist, a young American Glen Penfield, stumbled across an intriguing anomaly in the findings, strange opposing readings from a huge underwater arc with “extraordinary symmetry” in clear, almost concentric rings that extended for miles.
Circular features like these are of great interest to petroleum firms because some can trap vast amounts of oil and gas hence the term “oil traps”. This one was known for years in the industry, though initial studies by Pemex (Petróleos Mexicanos) had hardly been promising. Several initial exploratory wells were dug a mile down in the 1950s and 60s on land but the drills had struck nothing but crystalline rock and brought up andesite boringly common to a volcanic caldera.
In 1978, Pemex was trying its luck once more, when Penfield plotted, sketched the info and frowned, startled by the apparent strong magnetic force in the zone’s bulging centre and the contrasting low levels in the outer areas. Intrigued, he pulled up an earlier gravity map and realised that another mirror image spread out in the opposite direction exactly across the peninsula, forming a huge circle 110 miles wide centred near the small town or pueblo.
On land, this is pockmarked by weakened limestone deposits, the rim traced by an arc of sinkholes, called cenotes, the deep water natural sinkholes sacred to the Mayans.
Oil exploration is an expensive, risky and cut-throat business driven by economics and profit, so unsurprisingly, firms fiercely guard their potentially precious data of the fast-dwindling commodity, and daring detours for unrelated research are discouraged. No different, Pemex had a decade earlier confidentially asked a Tulsa, Oklahoma, contractor, Robert Baltosser, to take a fresh look at a few perplexing proprietary gravity surveys, but bound by the rules, he could not publicise his conclusion that it was a massive impact crater.
Excited and certain the shape had been created by a calamitous event in geologic history, Penfield wrote a report which was filed away. While the company disallowed the release of specific, classified data, it reluctantly let him and an official, Project Supervisor, Antonio Camargo Zanoguera, present their stunning results at the 1981 Society of Exploration Geophysicists conference, in Los Angeles.
“This was one of the greatest moments of my life” he said, according to the Oxford University Press’s publication “Impact!: The Threat of Comets and Asteroids” by Gerrit L. Verschuur. “This was the textbook example of an impact crater and it was unspeakably exquisite,” Penfield recalled. However the meeting was sparsely attended, although an oil industry reporter from the Houston Chronicle, Carlos Byars, picked up the story and ran with a front-page coup that received little attention. Penfield realised that without hard core samples to prove his hypothesis, he ran the risk of being branded a nut-case.
Other world experts were toiling independently, with one group insisting that the Mexican geologic oddity was due to a lava dome and volcanism. Byars tried but could not get requisite attention for the crater case at the many planetary and scientific conferences but he did run into an interested Arizona University graduate student, Adam Hildebrand, who was fascinated by the thick sheets of fireball and ejecta material in Haiti and widespread evidence of the consequent tsunamis concentrated in the Caribbean Basin.
In a serendipitous move for science, Byars would later link up Hildebrand with Penfield and the pair would embark on a dogged adventure to locate, secure and probe physical proof of the catastrophe through altered rocks like gray impact breccias and shocked quartz. Impact breccias are severe heat-blasted pieces as their Italian namesake suggest that look like broken stone pebbles confined in a concrete-type substance. Shocked quartz are marked when a space object hits the ground, and its powerful waves shoot through the tiny grains leaving a unique, indelible pattern of distinct parallel lines.
Finally, in March 2010, a panel of 41 scientists agreed the Chicxulub asteroid convulsion triggered the mass extinction that hastened the end of the dinosaurs and three quarters of all life.
Only earlier this month, Science Daily (SD) reported on a Potsdam Institute for Climate Impact Research (PIK) study that reconstructed how tiny droplets of sulfuric acid formed high up in the air after the crash, blocking the sunlight for several years, and profoundly influencing life on the third planet from the sun. Plants died, and death spread through the food web. New computer simulations show these droplets resulted in long-lasting cooling.
“The big chill following the impact of the asteroid that formed the Chicxulub crater in Mexico is a turning point in Earth’s history,” noted Julia Brugger, from PIK, lead author of the study. “We can now contribute new insights for understanding the much debated ultimate cause for the demise of the dinosaurs at the end of the Cretaceous era.”
In the tropics, annual mean temperature fell from 27 to 5 degrees Celsius. “It became cold, I mean, really cold,” stresses Brugger. Global measurements dropped by at least 26 degrees Celsius and the yearly figure was below freezing point for about three years. Evidently, the ice caps expanded.
“It is fascinating to see how evolution is partly driven by an accident like an asteroid’s impact — mass extinctions show that life on Earth is vulnerable,” adds co-author Georg Feulner who heads the PIK research team. “It also illustrates how important the climate is for all lifeforms on our planet. Ironically today, the most immediate threat is not from natural cooling but from human-made global warming.” Of course, this is mainly caused by greenhouse gases from the combustion of fossil fuels, like the old oil now found in Guyana.
ID enjoys cosmic and cursive writing with elegant fountain pens, still known as “Iridium-Points” even though these are no longer mounted in rare metal alloys that gave the iconic Parker 51 pen its special nib.
