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geochronometry

The determination of the length of time intervals. Geochronometric resolutions for zonations based on different organisms may be calculated by dividing the time-span of a series by the ...

stratigraphy

stratigraphy   Reference library

The Oxford Companion to the Earth

Reference type:
Subject Reference
Current Version:
2003
Subject:
Science and technology, Earth Sciences and Geography
Length:
2,127 words
Illustration(s):
1

...of the more recent geological periods is more accessible than that of very ancient times, and the problems encountered in the higher (i.e. younger) parts of the stratigraphical column tend to be different from those found below. As research continues and our methods of geochronometry improve, some of the problems may be resolved, but it remains a truism that the older rock formations, and especially those that have been severely deformed, are the more difficult to date and correlate. Stratigraphy, then, was originally concerned with rocks, that is,...

corals and related fossils

corals and related fossils   Reference library

The Oxford Companion to the Earth

Reference type:
Subject Reference
Current Version:
2003
Subject:
Science and technology, Earth Sciences and Geography
Length:
927 words
Illustration(s):
1

...temperatures at low as 1 °C. Corals are generally too long-ranged to be useful zonally, although they have been used in Europe in the Early Carboniferous, where A. Vaughan established a zonal scheme in 1905 based on corals and brachiopods. They have, however, been useful in geochronometry. Many rugose and scleractinian corals show fine daily growth increments, which are often grouped in monthly and yearly annulations by growth constrictions. Study of Palaeozoic corals by Colin Scrutton of the University of Durham (England) has indicated that there were an...

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