Gravel sheets in the suburbs of Washington, DC

Deborah Painter (USA) If you live in western Prince George’s County, Maryland in the USA, in the towns of Oxon Hill and Suitland and you want to dig to place a water line, plant a garden or excavate to construct a foundation for any building, chances are you will encounter sandy soil with hundreds of cobbles and boulders. Some boulders encountered could be in the form of large flattened slabs. You might be wondering why these are present, since these towns are in a coastal plain, far south and east of the rocky outcrops of the Piedmont area of Virginia and Maryland. For someone like me, who was born and raised in the Coastal Plain area of Virginia, these ubiquitous cobbles and boulders seemed out of character for the region. I discovered these odd boulders and cobbles when I joined a colleague from an office in a northern state to assist him in ecological studies for two small sites not too far from the United States Capital of Washington, in the District of Columbia (DC). Our goal was to help our client know if there were any threatened or endangered species, wetlands, hazardous materials or other site constraints, as this would assist the client to decide whether to purchase the properties. Our first Prince George’s County site for an ecological study was one of a few hectares in size in Suitland, a suburb of Washington, DC and approximately 8km southeast of the border of the capital city near the shore … Read More

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Fossil crustaceans as parasites and hosts

Adiël Klompmaker (USA) Who would like to carry a parasite? I bet not many people would like to have one or more. They are nevertheless very common in humans and in other organisms, and can affect entire food webs including keystone species. They tend to be small compared to the host and the vast majority of them are soft-bodied. Despite their small size and soft appearance, they can affect the host substantially, for example, leading to a reduced growth rate and less offspring. Much of the same holds true for crustaceans – they are affected by parasites and can act as parasites themselves. For example, parasitic crustaceans are found among the isopods and copepods. Given the widespread occurrence of parasitism in and by crustaceans today, a fossil record of such parasitism may be expected. Swellings in fossil crabs and squat lobsters So what does the fossil record look like? I have been fortunate to have worked on this under-studied field of research. During my PhD research, I found various swellings in fossil crabs and squat lobsters (decapods from the superfamily Galatheoidea) during and after field work in northern Spain in reef carbonates from the mid-Cretaceous (upper Albian). They appeared to occur regularly in the back part of the carapaces of these crustaceans. Fig. 1. Bopyrid isopods from the species Orthione griffenis (large female and small male), removed from the right gill chamber of a modern mud shrimp (Upogebia pugettensis). (Photo by Stephen Ausmus, USDA Agricultural Research Service, http://www.bugwood.org.) This swelling … Read More

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Giant trilobites and biotite nodules in Portugal

Peter Perkins (UK) The generally accepted reason for the fame of Arouca is Princess Mafalda, born 1195, who was responsible for the convent becoming Cistercian. Here is an interesting story – she was beatified in 1793. However, I won’t go into that now, but it is well worth investigating. For this article, there are other reasons for its fame, at least among geologists. Arouca is 38km to the south east of Oporto, in northern Portugal, and gives its name to one of two geoparks in Portugal. In Arouca Geopark (Fig. 1), which has an area of 330km2 (just a little smaller than the Isle of Wight), there are two quite remarkable geological features, one palaeontological and the other concerning igneous petrology. Fig. 1. Map of Arouca Geopark. A geopark is an area of significant size that has a particular geological heritage, with a certain number of sites of special importance – scientific quality, rarity, aesthetic appeal and educational value. It must also have a sustainable strategy for development to be accepted as a member of the worldwide network of geoparks. There are 42 in Europe, in 16 countries. The other Portuguese Geopark is Naturtejo, through which the River Tagus flows. There are nine geoparks in the British Isles, for example, NW Highlands (Scotland), Copper Coast (Ireland), Fforest Fawr (Wales) and the English Riviera. The website, http://www.europeangeoparks.org, gives website addresses for all. The geology of Portugal is very complex. There are no strata younger than Triassic, except for Holocene deposits in … Read More

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