i 3 6 MIDDLE ALBIAN STRATIGRAPHY 



European Subzonal sequence. In Texas, Young's carbonarium Zone does not con- 

 tain Lyelliceras and the possible conclusions that he poses are as follows (1966 ; 18). 



' 1. We do not understand yet the taxonomy and ranges of species of 

 Lyelliceras. After all, the entire family Lyelliceratidae is still little known. 



2. The rocks between the dentatus and nitidus subzones are greatly con- 

 densed in Peru, Venezuela, and Colombia. 



3. The beds in Texas without diagnostic ammonites (Upper Glen Rose and 

 lower Walnut Formations) are to be correlated with the dentatus and benettianus 

 subzones, and the zones of salasi and carbonarium are condensed and represent 

 all of the Folkestone section between the dentatus and cristatum subzones 

 (= beds II-VII, inclusive). " 0. " carbonarium is interpreted with such latitude 

 that it could include forms of the salasi zone of Texas. 



4. The ammonite zones are migrating against each other. In other words, 

 Lyelliceras is younger in South America than in Europe, and Manuaniceras 

 carbonarium is younger in Texas than in South America. This possibility will 

 be distasteful to orthochronologists, but it is a factor that cannot be overlooked 

 and is supported by the occurrence of Inoceramus concentricus with Lyelliceras 

 (Benavides, 1956, p. 414). 



I am inclined to look with favor on the first explanation, but it is a personal 

 preference. In the final analyses, some combination of two or more of these 

 explanations may seem preferable. I must point out, however, that Benavides' 

 (1956) section descriptions do not indicate condensation.' 



Unfortunately it is necessary to point out that the evidence for his correlation of 

 the Texas Middle Albian zonal sequence with that of the Anglo-Paris basin is non- 

 existent. The only direct correlation that can be made between the two areas is in 

 the cristatum Subzone. Dipoloceras fredericksburgense and D. cristatum are known 

 from the upper part of the Goodland Limestone in Tarrant Co. Texas. Inoceramus 

 subsulcatus was figured by Bose (1927; 189-193, pi. XVIII, figs. 1-5) from the 

 Edwards Limestone which is of the same age. But perhaps the most significant 

 link is provided by Oxytropidoceras cantianum Spath (1931 ; 350-1, pi. 32, fig. 5) 

 which is almost identical to the specimen of ' Manuaniceras carbonarium transitional 

 to M. peruvianum multifidum (Steinmann) ', figured by Young (1966 ; pi. 17, fig. 6) 

 and which is also from the upper part of the Goodland Limestone (= cristatum Sub- 

 zone). The only other possible link is provided by Dipoloceras of the cornutum group 

 also known from the Goodland Limestone (e.g. Spath 1931 ; 363 text-fig. 118). 

 Now we have the measure of the problem. Oxytropidoceras in the wide sense occurs 

 in the Anglo-Paris basin in the mammillatum Zone (Lower Albian), in the lyelli and 

 spathi Subzones (Middle Albian), and in the cristatum Subzone (Upper Albian) ; it is, 

 therefore, a very long-ranging group. 1 The development of the genus Lyelliceras is 

 now well known both in the hoplitinid province and outside it, and the evidence 

 indicates that the beds containing it in Pakistan, Madagascar, Algeria, Colombia, 

 and Peru are of the same age as those containing Lyelliceras in the Anglo-Paris basin. 

 Therefore, the specimens of ' Oxytropidoceras ' carbonarium from the lyelli Subzone 

 sediments of the Pariatambo Formation of Peru cannot be of the same age as those 



1 It is now known from the Loricatus Zone of north Kent (Owen in press). 



