Locations of individual study areas are described in the text. After Keppie (2000). The Appalachian orogen of North America is divisible with some controversy into five tectonolithologic zones which ...

The Late Paleozoic ice age has long been a climate enigma. Atmospheric CO₂ estimates for this period vary widely, and different reconstructions of the likely temperature vary by as much as 20°C.

A “demon-toothed” sea creature with “large, well-spaced fangs” has been identified as a new species after a researcher found a fossilized partial skull in the New Mexico desert, officials said. The ...