Vol­cano gave China its di­nosaur fos­sil trove

The Star Malaysia - Star2 - - SCIENCE -

A TREA­SURE trove of fos­silised di­nosaurs and other long-ex­tinct species in north-east­ern China was cre­ated, Pom­peii-style, by an erupt­ing vol­cano, sci­en­tists said last week.

A seam of rock known as the Yix­ian and Ji­u­fotang for­ma­tions, in western Liaon­ing prov­ince, is the burial ground of an as­ton­ish­ing ar­ray of crea­tures that lived around 120 mil­lion years ago in the Early Cre­ta­ceous.

Called the Je­hol Biota, it is the rich­est and widest source of fos­sils ever found.

It has yielded the re­mains of di­nosaurs, pterosaurs, early birds and mam­mals, as well as tur­tles, lizards, fresh­wa­ter fish, frogs, plants and in­sects, which in­hab­ited a long-gone vista of lakes and conifer forests.

Many of the spec­i­mens are as­ton­ish­ingly well pre­served, re­veal­ing even scales, feath­ers, hair or skin – a pre­cious find in­deed for palaeon­tol­o­gists.

The se­cret of the preser­va­tion, ac­cord­ing to a study led by Baoyu Jiang of Nan­jing Univer­sity in Jiangsu, lies in a bru­tal vol­canic episode that ex­tin­guished life all around and then buried it in dust, lock­ing it away for eter­nity.

Jiang’s team looked closely at 14 bird and di­nosaur fos­sils and the thin layer of dark­ish sed­i­ment in which they were found, at five lo­ca­tions.

The big killer, they be­lieve, was pyro- clas­tic flow – a vi­cious out­pour­ing of hot, suf­fo­cat­ing gas and su­perfine dust, mov­ing at gale-force speed.

Un­der the mi­cro­scope, de­bris from plants showed black­ened carbon streaks, and in the fos­silised skele­tons, hol­low bones were filled with fine quartz grains.

But the big­gest in­di­ca­tor of all came from criss­crossed cracks at the bone edges, caused by heat stress.

This phe­nom­e­non was also found in the bones of vic­tims at Pom­peii, the Ro­man town that was buried by an erup­tion of Ve­su­vius in AD79, the au­thors said.

Pre­vi­ous re­searchers had noted that the Je­hol Biota sed­i­ment was vol­canic.

They sur­mised that there had been a mass die-out as so many dif­fer­ent species – ter­res­trial, aquatic and avian – were all clus­tered in one area.

But sus­pi­cions that an erup­tion was to blame lacked hard ev­i­dence un­til now.

The dust flow from the vol­cano swept many dead crea­tures into lake beds, where they were im­me­di­ately buried in oxy­gen-starved con­di­tions, ac­cord­ing to the new study.

“Ter­res­trial ver­te­brate car­casses trans­ported by and sealed within the py­ro­clas­tic flows were clearly pre­served as ex­cep­tional fos­sils through this process,” said the pa­per, pub­lished in the jour­nal Na­ture Com­mu­ni­ca­tions. – AFP

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