Important Green River Formation fossils come to New York

Stuart Wilensky and Douglas Miller (USA) In the early Eocene Epoch, drainage from the newly uplifted Rocky Mountains filled an inter-mountain basin to form what geologists call Fossil Lake. The climate of Fossil Lake was subtropical, similar to the climate of Florida today. The lake persisted for about two million years, and was home to palm trees, turtles, birds and an abundance of fish. On numerous occasions, unique conditions came together to result in some of the best-preserved fossils ever discovered. The sediments of Fossil Lake were first discovered in the 1860s, near the town of Green River Wyoming, and the area was named the “Green River Formation,” which is well-known in the scientific community and by amateur collectors. Palaeontologists have long theorised that the lake was deep enough to be anoxic (devoid of oxygen) at the bottom. This prevented scavengers from disturbing the plants and animals, and inhibited decomposition. Algae, and other plant and animal life, would die and fall to the bottom as in lakes and ponds today. Storms brought runoff from the mountains, covering the flora and fauna with mineral-rich material that would ensure their preservation. Recently, scientists have asserted that a kind of “red tide” may have been responsible for the many perfectly preserved fossils found. (“Red tide” is a common name for algal blooms, which are large concentrations of aquatic microorganisms, such as protozoans and unicellular algae. These can cause a severe decrease oxygen levels in the water column, leading to mass mortality events.) We … Read More

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Jurassic Coast (or is it?) with the Geologists’ Association

Mervyn Jones (UK) Since 2012, the Geologists’ Association (GA) has put on annual field trips to the Dorset coast led by Prof John CW Cope (of the National Museum Wales), who is author of the definitive Field Guide No 22. The second edition was published in April 2016 (Geology of the Dorset Coast (2nd ed)). In fact, the trips were started to celebrate the publication of the first edition of the guide. The Dorset Coast is often equated with the ‘Jurassic Coast’ when, in fact, the geology stretches from the topmost Triassic, near the Devon border, through Jurassic and Cretaceous successions, to Eocene deposits at Studland. For this and other reasons, it attracts amateur geologists in large numbers. John’s guide provides essential information including descriptions of the succession and practical guidance about access. What’s missing are the entertaining stories that John Cope can provide and the context provided by exploring inland a bit. Day 1 – Saturday (1 October) For our fifth field meeting, we met up in Lyme Regis (in the car park next to the newly-restored house originally owned by John Fowles – see below) – a town to stir the heart of any geologist. Our mission for the weekend was to look at the unconformity below the Cretaceous, as it oversteps the older Jurassic and Triassic strata progressively in a westerly direction. En route, we observed the instability of the cliffs and suffered the same ourselves, as we scrambled over the boulders and shingle. On this occasion, … Read More

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All change at Selsey, West Sussex, UK

David Bone (UK) Issue 26 of Deposits magazine in the Spring of 2011 included my article on fossil collecting at Bracklesham Bay in West Sussex, following in the footsteps of my guide book on Fossil hunting at Bracklesham & Selsey, published in 2009. This area has been well known for the foreshore exposures of Palaeogene and Quaternary geology since the mid-nineteenth century and is still very much an area for popular fossil collecting, as well as research. Many readers will have been to Bracklesham or Selsey to collect sharks’ teeth and may have even been lucky enough to find a piece of mammoth bone or tooth. The scientific value of the area is recognised by much of the coastline being designated as a geological Site of Special Scientific Interest (or SSSI). However, this has been impacted by two major coastal defence schemes at Selsey that were completed in 2013, significantly changing access to the foreshore and any exposures of the geology, as well as rendering my guide book in need of a major update. In medieval times, Selsey was effectively an island, although this is no longer the case due to the construction of sea defences and land reclamation. However, Selsey remains a localised area of higher land surrounded by low-lying land prone to flooding (Fig. 1). It has also been an area of coastal erosion and loss of land to the sea throughout recorded history. The relatively unconsolidated Palaeogene and Quaternary sediments exposed in the low cliffs of the … Read More

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Fossil sea urchins from the Middle Eocene of the Bartonian of Christchurch Bay, UK

David N Lewis (UK) The spectacular fossil gastropods and the teeth of sharks – found at the type locality of the Middle Eocene Bartonian in Christchurch Bay (Hampshire and Dorset) – overshadow the other fauna and flora found there. However, among the ‘Cinderella’ groups are the echinoids (sea urchins). Several kinds, both ‘irregular’ and ‘regular’, can be found, some preserved with superb detail. Fig. 1. Sketch maps to show the location of Barton-on-Sea (modified after Lewis & Donovan, 2008).The coastal holiday resorts of Christchurch Bay, near the New Forest, include Highcliffe to the west, Milford-on-Sea to the east, and the well-known Barton Cliffs of Barton-on-Sea between the two (Fig. 1). All lie within the Hampshire Basin of southern England. This coastal stretch is famous for its extensive range of well-preserved Eocene fossils found in the sea cliffs and on the foreshore. The most fossiliferous area is sometimes referred to simply as ‘Barton’, and the clays and sands in which the fossils are found as the ‘Barton Beds’. Of particular interest to fossil collectors, students and holiday-makers alike are the abundant fossil molluscs and the teeth of sharks. However, there are other fossils too, including plants, microfossils, a wide variety of other invertebrates such as bryozoans, brachiopods, corals, crabs, echinoderms (brittle-stars, starfish and sea urchins) and worms, and vertebrates including fishes, reptiles and rare mammals (see Hooker, 1986). Trace fossils can also be seen in the clay sequences. In fact, some of the clays allow considerable fine detail of the fossils … Read More

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Mammoths in the freezer

Adrian Lister (UK) As palaeontologists, we are used to relying on the preserved hard parts of extinct organisms – shells, bones, teeth and so on – to reconstruct their appearance and adaptations in life. The reconstruction of soft tissue relies upon our knowledge of related living forms, plus clues such as the scars of muscle attachments on bones or shells. Exceptions include body outlines preserved in the fine-grained sediments of Lagerstätte, such as in the Eocene of Messel (Germany) or the Cambrian Burgess Shale (Canada); or, even more rarely, organisms preserved in 3D, of which the most familiar source is Tertiary amber. Among mammals, the most celebrated case of exceptional preservation is provided by the carcasses preserved in permafrost in Siberia (Russia), Alaska (USA) and the Yukon (Canada), at localities lying almost exclusively north of the Arctic Circle (Lister and Bahn, 2007). Almost all date to the last glaciation, with radiocarbon dates typically in the range 50 to 10,000 years ago. Species from which partial or whole carcasses have been recovered include bison, horse, wolverine, woolly rhinoceros and, above all, the woolly mammoth. The reason for the preponderance of these is unclear, although it may partly be a matter of reporting bias, other species being considered less interesting or less valuable when discovered by local people. Even so, not more than a dozen or so complete or largely complete mammoth carcasses have been recovered to date. While Siberian natives have doubtless been finding these remains for millennia, the first carcass … Read More

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Fossil collecting at Bracklesham, West Sussex

David Bone (UK) “I have been greatly disappointed … [owing to] sand, sometimes two to three feet in thickness, or the tide not leaving the shore sufficiently exposed; so that a stranger might conclude that there were no fossils to be procured at Bracklesham”. The Sussex geologist, Frederick Dixon, writing about Bracklesham in 1850 warned readers with these words and it is no different today. Exposures of the richly fossiliferous Palaeogene sediments, which comprise the Bracklesham Group (Eocene), come and go unpredictably with the tides and weather. On a good day, extensive shell beds, around 46 million years old, cover the beach and sharks’ teeth may be found by the hundred. On a bad day, Dixon’s quote is all too true. Fig. 1. Location map for Bracklesham Bay, West Sussex. Bracklesham Bay is located seven miles south of Chichester in West Sussex, on the south coast of England (Fig. 1), at the eastern end of the syncline known as the Hampshire Basin. To the north, beyond Chichester, the ground rises to the Cretaceous chalk hills of the South Downs, while, to the south, across the waters of the Solent, the Isle of Wight stretches across the horizon. It is often said that if you can see the Isle of Wight, it is going to rain. If you can’t see it, then it is raining. This is a fair warning to anybody planning a trip here – this balmy stretch of coast, even on a sunny day, takes the full brunt … Read More

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