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Fossils down under or finding fossils in boreholes

Dr Susan Parfrey (Australia) You may be familiar with collecting fossils from eroded rock surfaces, a riverbank, a road or rail cutting, a cliff face or a fresh cut surface such as a quarry. But there is another way fossils can be recovered – from boreholes. Boreholes have been drilled in Queensland for many years for exploration and to investigate the regional geology. Since Queensland is a relatively flat part of Australia, outcrops can be hard for geologists to find. Therefore, drilling offers a way of studying sub-surface geology that assists in the understanding of the stratigraphy of the State. Usually, drilling does not produce usable macrofossils. The process of drilling normally involves pushing a mud mixture down the borehole and over the bit, for cooling and lubrication. In this process, larger fossils are forced to the surface in the drilling mud and are broken into small pieces making them impossible to identify. However, microfossils can be recovered, as they are so small they are undamaged by the drilling process and are recovered at the surface to be identified and used in biostratigraphy (to date and correlate rocks). However, in Queensland, drilling was undertaken by the Geological Survey that retrieved lengths of core which provided access to deeply-buried strata and allowed recovery of both micro and macrofossils. Exploration companies also often retrieved short lengths of core at specific levels of interest, which sometimes contain fossils. Before a borehole is drilled, considerable geological mapping of the surface is undertaken. Only then … Read More

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The fossil forest of Curio Bay

Heather Wilson (New Zealand) Fig. 1. The location of Curio Bay. The 180 million year old fossilised forest at New Zealand’s Curio Bay is of international geological significance. When I visited the area recently, the wind was blowing a gale and there were high seas. There is a two-minute walk from the car park to a lookout and then a series of steps down to the beach. When the rocks and fossilised trees are wet, they are slippery, so you need good footwear. This is a protected area. When I visited, there was a representative from the Department of Conservation guarding the beach. There are also video cameras keeping an eye on the fossilised forest, making sure it doesn’t gradually vanish as a result of tourists and rock hounds making off with specimens. Fig. 2. View of Curio Bay. This is one of the most extensive and least disturbed examples of a Jurassic fossil forest in the world. The area within which it is found stretches for about 20km, from Curio Bay, south-west to Slope Point. When the forest was living (during the Middle Jurassic epoch), New Zealand was part of the eastern margin of the ancient super-continent known as Gondwana. North of Curio Bay, most of the country’s future land area was beneath the sea. The fossilised trees occur in green sandstones, alternating with blue shaley clays containing plant impressions. Silica has entirely replaced the woody structure of the trees and rendered them extremely resistant to erosion. Therefore, they … Read More

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Drought in South Australia creates soil problems

Dr Paul Shand (Australia) In South Australia, the staff of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Land and Water have recently shown that the River Murray, adjacent wetlands and the Lower Lakes (Alexandrina and Albert) close to the Murray Mouth are being seriously impacted by a combination of low water levels and the presence of acid sulfate soils (ASS). The Lower Lakes and the floodplains below lock 1 at Blanchetown are undergoing their first drought since the introduction of barrages more than 50 years ago. Lakes, such as Lake Bonney and Lake Yatco, as well as several wetlands formed by the River Murray, are being isolated as one option to generate water savings and help mitigate drought-related problems in the Murray-Darling Basin. Field observations and chemical analysis confirm the occurrence of both sulphuric materials (pH <4) and sulphidic materials (high sulphide concentrations and pH >4) in a range of ASS subtypes (Fig. 1). Fig. 1. Acid Sulphate Soil with sulfuric material near Swanport adjacent to the Murray River. In addition, some areas contain ‘monosulphidic black ooze’, that causes rapid oxygen depletion of lake and drainage waters when the ooze is mixed with oxygenated waters during disturbance (Fig. 2). Fig. 2. extensive cracking and accumulation of white and yellow Na-Mg-Fe-Al-sulphate-rich minerals or salt efflorescences. Unpleasant smells (‘rotten eggs’), as a result of rotting vegetable matter and the release of gases, have been experienced in these areas of exposed soils when water levels are extremely low or the lakes have … Read More

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Jurassic Gorge

By Dr Susan Parfrey About 95km south of Rolleston, in the southern part of central Queensland, Australia, is a national park that contains the Carnarvon Gorge. The gorge is over 32km in length and is formed of towering white sandstone cliffs. It has almost everything a visitor could want – beautiful scenery, wonderful Aboriginal rock paintings and a garden of moss with a magic waterfall, plus King Ferns, the largest ferns in the world. So what’s missing? Well, obviously, Jurassic dinosaurs. An impression of how these dinosaurs may have looked. © SMP. This is one of the most popular national parks in the state and has over 30,000 people visiting every year. Over the years, you would imagine every centimetre of rock has been carefully studied and, in particular, the ‘Art Gallery’ Aboriginal rock paintings, some of which date back 3,600 years. Imagine the surprise in 1992 when some tourists told the Park Ranger they thought there were bird footprints in a rock at the Art Gallery. The ranger examined the site and, sure enough, there were some marks on the rock. But were they footprints? The Park Ranger took photographs and sent them to the sloe palaeontologist at the Geological Survey of Queensland in Brisbane. Map of Australia showing the position of Brisbane and Carnarvon Gorge. Throughout my career as a geologist, I have seen every shape possible formed in rocks. Nature has an amazing ability to cut interesting shapes in natural objects. Combine this with people’s imaginations and … Read More

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Mineral collecting ‘Down Under’

Tony Forsyth (Australia) I got the collecting bug at about eight years of age, collecting (or ‘fossicking’ as it is called in Australia) fossilised sharks’ teeth and ancient whalebones eroding out of beach cliffs in my hometown of Melbourne, Australia. Some forty plus years later, I’ve still got the bug. … Read More