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SUMMER 2002 - This month from Architects of Eternity

Alvarez and team  

The father, the son and the sleeping hills of Umbria, Lat 43.25N, Long, 12.32E. Sometime in the early 1980's

The hills above Gubbio slept as they always have. The occasional chirp of a cricket the only noise to invade the silence of the long road that winds between steepening cliffs of limestone. The Bottaccione Gorge is a very different place though to the Contessa Highway - a mile to the east over the mountain. There the roads vibrate to the rattle of huge lorries transporting limestone from the quarries on the west side of the valley. And the Bottaccione does not have anything like the snake pit that the Contessa has. A deep, uninviting little gully that smells of cat pee and digs deep into the succession just to the north of the K-T boundary. And so Walter Alvarez and his new team from the Renaissance Geology Group at Berkeley are grinding their way up the hill out of Gubbio along the Bottaccione Gorge to where the bar is. It's closed. No surprises there: the bar at the bend in the Bottaccione always seems to be closed these days. Perhaps the owner's retired on the profits of geotourism? In fact a beer would have been nice, if only to break the journey before they introduce the old man to the clay layer. His father is in the passenger seat but he seems cool: Luis Alvarez is winding down, his volatility cooling with the passage of the years, like an old volcano as the magma vents close up. As a young man he was incandescence personified among the firebrand glitterati, nothing less than a physicist on the Manhattan project. And then he went on to the work for which he won his Nobel in 1968, the discovery of several subatomic particles. But that was all behind him now. He's here to celebrate his swan-song, his final if perhaps not his greatest achievement. A piece of good solid, geological research that he would never have got into if his boy had not decided all those years ago to become a geologist.

The jeep grinds further up the road, the cliffs of red and white limestone slashed at regular intervals of a metre or less by narrow fibres of brown clay, technically known as marl. Eventually the road curves gently into a bend and there Walter pulls off, climbs out, stretches and look around. He spreads out the map on the bonnet of the car. The silence is absolute, deep, eerie, punctuated only by the click of cooling metal. They aren't the first people to have been here. The gorge has been well known since the Italian geological survey mapped it in the aftermath of the second world war. Then, in the 60s a young micropalaeontologist from Milan logged the succession of microfossils along it and discovered an enigmatic clay band about half-way along the length of the gorge.

In the 1970s the gorge was host to the attentions of two of the brightest geologists of their generation - Pete Scholle and Mike Arthur - who showed that the particular era boundary exposed in these rocks is associated with a major upset in the carbon cycling of the oceans. But it is since 1980 that this place has become the most famous shrine to geological science in the world.

Walter remembers that for him this all started with something far more prosaic, even if it was a 'solid' piece of science. He had originally been interested in the palaeomagnetism of the area but then became interested in measuring sedimentation rates - the speed with which particles of sediment float down from the surface of the ocean especially in the interval represented by the clay layer. This was the K-T boundary, the division between the Mesozoic and the Cenozoic. Sedimentation rates have historically always been a difficult thing to measure. Fundamentally it boils down to only two things - knowing where undisputed time markers are in the sequence of (often otherwise undistinctive) strata, and then knowing the thickness of the sediment between these two time lines. By calculating the difference you get the sedimentation rate. As Walter leans back against the jeep and stares down the hill towards the bend it occurs to him again that this is nothing less than the history of stratigraphy. To know time and thickness of rock is to know the nature of time itself - the fundamental essence of palaeontology.

But the way that they tackled the problem of trying to measure the sedimentation rate in a clay layer only a few centimetres thick - the one place in the Bottaccione Gorge sequence where there were no forams to date the sequence - now that stemmed from the fertile, restless brain of his father. Luis' hypothesis had been: what if there were an independent measure of the rate at which sediments accumulated? Suppose, for example, that it was not necessary to know where the time horizons in a rock sequence were. Suppose instead that your measure of time came from somewhere else entirely.

It was a physicist's solution. Unencumbered by a formal geological education Luis had a fundamentally different approach to the problem - a different 'take' if you will - and consequently saw things from a more flexible perspective.

Walter realises that now, realises that by inviting his dad to get involved with his own work, he has been responsible for a seismic shift in the history of palaeontology. Probably the biggest one since Harold Urey unlocked the key to fossil climate research three decades before. Palaeontology has come out of the closet. Palaeontology now talks to other disciplines on an equal footing.

Luis is out of the jeep know, walking toward him. Walter leads him down the hill. The limestone ribs are interrupted here by a great trench dug in the cliff. This part of the succession used to be level with the rest. The trench is the result of the legion of geologists who have descended on this place since the mid-1970s. They excavated it so deep that you now have to lean far into the rock to find what you came for.

The rock around this area looks too as though it's been in a war. Everywhere it is pocked by perfectly circular holes an inch across. Legacy of the palaeomagnetists and the pestilential rock-drills they use to collect their samples. So many palaeomag samples have been taken that in only five years this once pristine outcrop has been converted into something that looks disconcertingly like either a gruyere cheese, or maybe that car that Bonnie and Clyde met their maker in at the end of Peckinpah's film.

And then Luis leans in close and peers into the bottom of the trench. It's hard to locate in the high sunlight of the middle of the day but Walter points it out and eventually he sees it. There at the very bottom is a narrow band - only a couple of centimetres wide - of reddish brown clay. It comes up out of the ground at his feet, extends through the trench and continues on up the cliff face out of reach. The cause of all the excitement - the Cretaceous-Tertiary boundary clay. The famous outcrop of the K-T boundary in the Bottaccione Gorge where Luis and Walter Alvarez discovered the iridium anomaly which led to the asteroid impact theory of the extinction that killed the dinosaurs.

Architects of Eternity

Extracted from Architects of Eternity by Richard Corfield. Published by Hodder Headline, ISBN 0-7472-7179-8.

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Richard Corfield 2003 in association with pedalo.co.uk