48 STUDIES IN GEOLOGY, No. 4 



gypsum that occurs along bedding planes throughout the 

 specimen. 



"In thin section rather sandy and full of small accretions 

 of tiny, hematite spherules, which were very probably origin- 

 ally sulfide (pyrite). In one place a lamina of gypsum par- 

 allel to the bedding appears in the thin section. There are 

 hints of extensive silicification, but I cannot prove it; the 

 hardness of the shale makes it most probable. 



"I would conclude that this was originally a carbonaceous 

 sulfidic (pyritiferous) shale, which for some reason (perhaps 

 because it was adjacent to a plane of tectonic movement?) 

 has been the locus of active water circulation which has oxi- 

 dized the carbon and sulfide originally present, formed gyp- 

 sum by means of sulfuric acid derived from the sulfide and 

 produced extensive silification." 



ANALYSIS OF THE FLORA 



An analysis of the previous and present contributions 

 results in the following list of generic plant types from the 

 Mesozoic of Peru : 



Equisetites 



Tseniopteris 



Ruffordia 



Filicites 



Cladophlebis 



Sphenopteris 



Weichselia 



Klukia 



Otozamites 



Zamiostrobus 



Cycadolepis 



Podozamites 



Thuites 



Brachyphyllum 



Antholithus 



The majority are poorly characterized and those which 

 are not are the Ruffordia, Weichselia, Klukia and the two 



