For thousands of years, fossilized tree resins known as amber have fascinated jewelers and inspired the scientific imagination. Especially in the last 200 years, paleontologists have turned to amber to better understand the distant past; By studying the amazing fossils preserved within them.
Have questions about amber? We will answer them here.
What is amber and how do fossils come out of it?
Plants secrete various viscous liquids; For example, latex, gum and wax. Some plants, usually woody plants, produce resin: a complex, viscous substance that is insoluble in water and hardens in contact with air.
Resins cover the wounds of plants and act in a way similar to our blood platelets. When a resin-producing tree is injured or has a break in its surface—such as a crack along a tree trunk—resin oozes from that area. When the resin is exposed to air and baked in the sun, it begins to harden. This process creates a protective layer in the tree wound that keeps out fungi and other pathogens.
Because the resin is sticky, when it oozes out of the tree trunk, drips onto the ground, or even flows out of the tree’s roots, small animals can become trapped in it. At times, some of these droplets enter the water; Maybe the tree is on the shore of an ocean or lake, or maybe a flood washed a tree into a river. Some of these resin droplets in water are buried in sediments; Like the sand of a flood plain or silt on the bottom of a lake.
Over thousands of years, the deeper the resin is buried, the more pressure and heat it feels. In a long period, these conditions cause polymerization of resin compounds; That is, they enter into chemical reactions with each other that create a multitude of chemical bonds.
This process results in a hard, glassy substance called amber, which can also hold the shape of any tiny creature trapped in the resin with amazing tenacity.
How long does it take for the resin to turn to amber?
It is difficult to say the exact time. The conversion of resin to amber is ultimately a product of the conditions experienced by the resin drop. However, in general, amber is usually much older than 40,000 years.
Any rock younger than this is likely to be in the Copal category; An old, polymerizing resin that still has some of the characteristics of a fresh resin, such as a tackier surface.
What fossils are found in amber?
Because amber can enclose and protect even soft-bodied animals, it is excellent at preserving the smaller, squishy inhabitants of forest ecosystems.
For nearly two centuries, paleontologists have been able to find insects, arachnids, crustaceans, plants, fungi, nematodes (tube worms), plants, microorganisms, and even fragments of larger vertebrates by studying amber.
But as you might have guessed, the fossils that emerge from amber are usually animals that were more likely to be buried in the resin of an ancient tree.
Where are fossils found in amber?
There are more than 160 sites around the world where copal or amber has been found, and the oldest amber on Earth, discovered in the Illinois Coal Gap, is about 320 million years old. However, these pieces of amber are on average less than half a centimeter wide and there are no fossils in them.
Among all the earth’s amber deposits, only about a dozen have diverse fossils. Almost all of these fossil deposits are about 125 million years old or younger, with only one known exception: a 230-million-year-old amber deposit in the Italian Alps that contains one fly species and two mite species.
What are the most studied amber deposits?
Baltic amber According to estimates, it is between 34 and 38 million years old, although some of its deposits were formed earlier. This amber is exposed by the erosion of the sediments of the northern coast of the Baltic Sea in Europe, and the most studied sediments are from the Kaliningrad province of Russia.
More than 3,500 species of fossil arthropods have been found in Baltic amber; Including more than 650 species of spiders. In rare cases, Baltic amber also contains vertebrate fossils – including a species of gecko lizard, Yantarogekko balticus, dating to about 54 million years ago.
This amber deposit also has fossils of plants; Among the oldest known fossils is a flower inside amber.
Dominican amber It is believed to be between 15 and 20 million years old, although its exact age is disputed. Scientists have found more than 1,000 species of fossils in this amber; Including more than 400 species of insects and 150 species of spiders. Sometimes fossils of vertebrates are also revealed; including anoles and even a salamander.
Burmese amber It is about 99 million years old and comes from mines in northern Kachin state in Myanmar that have been exploited for the gem trade for the past 2,000 years. Scientific interest in Burmese amber has reached its peak in the last two decades; Because paleontologists have uncovered a very diverse ecosystem: carnivorous “hell ants” caught between meals, a piece of a feathered dinosaur’s tail, the shell of a sea creature called an ammonite, and even an ancient baby bird.
Of course, scientists also disagree on the ethics of studying Burmese amber. Kachin amber mines have been the scene of conflict between the Myanmar military and local independent groups for decades, and except for a few scientific studies of Burmese amber, there is no mention of Myanmar authors.
Canadian amber It is between 78 and 79 million years old and comes mainly from a site called Grassy Lake in western Alberta province. More than 130 different species of fossils have been found in this amber, many of which are aphids or mites. But some pieces of amber contain pieces of conifer needles, fungi, pollen and even feathers of birds and dinosaurs.
