Specialist Eryn Brobyn takes a closer look at a large and extremely rare fossilised palm frond excavated from a desert in Wyoming — and explains what it tells us about life at the time
The palms of the Green River Formation, a geological structure covering parts of Wyoming, Colorado and Utah in the United States, represent a flora bordering a warm freshwater lake 50 million years ago. To put this period into context, this giant palm frond was growing at a time when the Rocky Mountains were still forming — some 15 million years after the dinosaurs had been wiped out.
‘Plant material is amongst the rarest in the fossil record, because it begins to decompose quite quickly unlike, say, bones or whole skeletons,’ explains Eryn Brobyn, junior specialist in the Travel, Science and Natural History department at Christie’s. ‘These palms are amongst the largest and finest preserved I have seen. As well as its size and rarity, this fossil is notable for its superb detail in the veining of the frond and it’s coal-like colour.’
Excavated in the 1990s, the palm frond provides extensive information about what the desert region of Wyoming would have looked like during the Eocene epoch. ‘We can tell from this fossil that the area would have had a moist temperate or sub-tropical climate, with temperatures at around 20-30 degrees centigrade,’ says Brobyn.
This frond is likely to have fallen into a lake and sunk to the bottom, whereupon rather than decomposing it would have been covered, and therefore preserved, in volcanic ash. Over many millions of years the mud and ash in the lake would have turned into limestone, in which all fossils, including the fish from Green River pictured below, are found.
‘These fossils remind me of memento mori,’ remarks Brobyn of the palm, ‘and would work perfectly as part of a cabinet of curiosities or as a graphic work of art. I have seen many framed examples of fossils from the Green River Formation, and could certainly imagine enjoying this stunning piece in my living room.’