The Piedra Chamana Fossil Forest, near the village of Sexi in central Cajamarca, records the vegetation of the South American tropics 39 million years ago, early in the New World tropical forests history and before the rise of the present-day Andes. In this fossil forest, notable discoveries have included the mangrove genus Avicennia, a genus of emergent forest trees (Cynometra), and the second dipterocarp known from the New World. The significance of the fossils rests on the unique circumstances of preservation, the detailed reconstruction of the forest and environment that is possible based on the plant fossils and ancient soils, and the importance of this record for the study of climate change. Sites like the fossil forest are particularly vulnerable to disturbance and loss of the fossil resources. Ongoing monitoring shows that human activities and erosion are having serious effects a...

The Piedra Chamana Fossil Forest, near the village of Sexi in central Cajamarca, records the vegetation of the South American tropics 39 million years ago, early in the New World tropical forests history and before the rise of the present-day Andes. In this fossil forest, notable discoveries have included the mangrove genus Avicennia, a genus of emergent forest trees (Cynometra), and the second dipterocarp known from the New World. The significance of the fossils rests on the unique circumstances of preservation, the detailed reconstruction of the forest and environment that is possible based on the plant fossils and ancient soils, and the importance of this record for the study of climate change. Sites like the fossil forest are particularly vulnerable to disturbance and loss of the fossil resources. Ongoing monitoring shows that human activities and erosion are having serious effects a...

The Piedra Chamana Fossil Forest in northern Peru, which is associated with Calipuy volcanics dated at 39 Ma, includes a large amount of fossil wood occurring across an 8-km-long area. In one part of the site, woods are weathering out of a volcanic mudflow (lahar) deposit and in growth position in an underlying ashfall that also contains fossil leaves. The general geologic context and inferred taphonomy of the fossils has been described in Woodcock et al, 2009. Recent fieldwork, and ongoing studies of the fossil material, has added to our understanding of the assemblage and also shown that fossil sites are more extensive than had been thought. Analysis of the fossils and their spatial occurrence indicates that three plant associations are represented at the sites we have studied most intensively (Fig. 1): • 1) Lowland tropical forest with a diversity of monocots and dicots. Preliminary...