604 T. W. STANTON MESOZOIC OF MEXICO AND CENTRAL AMERICA 



in several widely distributed areas^ cycads and other land plants were 

 embedded in non-marine deposits. Xewberry has described some of these 

 plants from Honduras and from Sonora as Ehietic, and somewhat similar 

 floras have been described by Logano as Lower Jurassic (Liassic) from 

 the States of Vera Cruz and Puebla, and by Wieland from the State of 

 Oaxaca. Non-marine deposits similar to those containing the plants are 

 distributed through Chiapas, Guatemala, Honduras, and Nicaragua. 

 (Incidentally it should be mentioned that in AVillis's Index to the Stra- 

 tigraphy of North America, page 500, through an error in transcription 

 or proof-reading, Sapper is made to call these rocks marine. The original 

 word is Mergel, which of course was translated marls.) The length of 

 the epoch or epochs represented by these plant-bearing deposits and their 

 exact place in the general time scale must be determined by further 

 studies and discussions by the paleobotanists, supplemented by thorough 

 investigation of the stratigraj^hy of each area involved. Meanwhile these 

 floras may be used as proof of extensive land areas near the close of the 

 Triassic and continuing into Jurassic time. 



Jurassic 



That the plant-bearing beds of southern Mexico just mentioned are 

 actually of Jurassic age seems to be established by their association with 

 marine beds containing characteristic Jurassic ammonites. According to 

 Bose, those of Puel)la are lower Liassic, while those of Oaxaca described 

 by Wieland are in part Middle Jurassic, perhaps extending down into 

 the Tipper Liassic. Bose reports marine Liassic beds with Arietites and 

 a varied molluscan fauna in northern Puebla and neighboring parts of 

 Hidalgo and Vera Cruz at elevations of over 2,000 meters, and another 

 possible occurrence of marine Liassic in Oaxaca. All the other known 

 areas of marine Lower Jurassic in North America are confined to the 

 Pacific border north of Mexico, and the imperfectly known fauna seems 

 to be sufficiently related to that of Europe to indicate direct connection. 

 The marine deposits in southern Mexico strongly suggest that the inter- 

 oceanic passage was in that region. 



Similar conditions prevailed in Middle Jurassic time, when the faunas 

 of the Pacific coast of the United States were related to those of the 

 Mediterranean region, and the presence of marine Middle Jurassic sedi- 

 ments in Oaxaca and Guerrero indicates that the interoceanic connection 

 may have been across southern Mexico. 



The wider disti'ibution of Upper Jurassic sediments in Mexico, in 

 Cuba, and in west Texas seems to indicate a greater submergence than at 

 any previous epoch in the Mesozoic era. Marine rocks of Upper Jurassic 



