OLD, GOLD AND GORGEOUS
Plants and animals trapped in amber create a minute in time that is preserved for tens of millions of years. PAUL WILLIS reports.
Fossils in amber show life 99 million years ago, writes PAUL WILLIS.
IN GREEK MYTHOLOGY, they were thought to be the tears of the sisters of Phaëton, son of Helios, the Sun God. They were included in jewellery as far back as the Neolithic period. They first appear in the literature in the fourth century BCE in the writings of Theophrastus and, later, Pytheas. Their honey- gold transparent allure has transfixed people for thousands of years. And now amber, and its occasional cargo of fossil inclusions, is retelling the story of life in exquisite detail.
The origin of amber is much more prosaic than the tears of the gods. It started out as dribbles of plant sap, perhaps fallen to the forest floor in sticky blobs. Once buried in sediment, the sap undergoes molecular polymerisation,
hardening under heat and pressure to form, first, an intermediate substance known as copal, and then amber itself. But it’s while still freshly exuded and viscous that it sometimes ensnares a hapless passing creature, trapping it forever.
The oldest amber dates back 320 million years to the Upper Carboniferous period. There are hundreds of localities all over the world that produce these glassygolden stones, but only a few produce specimens with fossils trapped within.
The largest deposit of amber comes from the Baltic region, which covers eastern Germany, Poland and Russia. Recent analysis shows that the original resin came from a rare group of conifer trees, of which there is only one species alive today – the Japanese Umbrella pine ( Sciadopitys verticillatei). Although recovered from marine sands dated as 25 million years old, analysis of the insects occasionally found in Baltic amber reveals that it is considerably older still, dating from between 44 and 49 million years ago.
The Dominican Republic in the Caribbean is renowned for producing yellow, gold and rare blue amber of exceptional clarity. It also produces more fossils, particularly of insects, than the Baltic variety. Dating to around 25 million years ago, the environment in which the sap was produced was a tropical forest filled with lianas, shrubs and large trees. The sap itself can be traced back to the now- extinct species of tree, called Hymenaea protera, from a genus that can still be found growing in the tropical Americas and the east coast of Africa today.
But most of the spectacular fossils recovered over the past decade or so have come from Myanmar – where almost a third of specimens unearthed contain all or part of a once-living creature. This amber has been mined for jewellery since the first century CE. Most of it comes from Hukawng Valley in Kachin State in the north of the country. Today there is a large, unregulated industry mining Myanmar amber and most of the prized fossil specimens are sold to private collectors, often putting them out of reach of scientific study.
Myanmar amber contains a huge variety of animals and plants from a 99-million-year- old tropical forest. This was a time, late in the Age of the Dinosaurs, where many types of animals and plants were undergoing significant changes, and we see the first appearance of several groups that are familiar to us today.
The beauty of amber as a medium for creating fossils is that it forms a perfect impression of the surface of the creature or plant entombed within. The body of the animal decays to carbon that can line the cavity created by the original form. The fidelity of the surface impression is so high – and the size of many of the creatures is so small – that the fossils can be scanned and then blown up to reveal the tiniest details.