12 Windhausen — The Cretaceous-Tertiary 



connecting South America with Australia, New Zealand 

 and (?) Africa. According to him, this fauna is littoral 

 and migrated along the shelf of a continent, or at least 

 over a shallow sea between large islands of more or less 

 continental character. Hence the surprising resem- 

 blance between the Australo-New Zealand and Pata- 

 gonian molluscan faunas. In connection with this 

 phenomenon attention may be called to the fact that in 

 the Santa Cruz Beds an increasing relationship of the 

 Patagonian terrestrial faunas to that of Australia has 

 been observed, while more and more exchanges of faunas 

 between these provinces are postulated. 



On the other hand, a peculiar contrast results from a 

 comparison of the older Patagonian transgressions with 

 the last one, which is represented by the Parana Forma- 

 tion (Piso Paranense, Formacion de Entre Bios etc.) 

 determined by Borchert 33 as of Pliocene age. Here the 

 fauna is entirely different from that of the Patagonian 

 Formation. It resembles the Upper Tertiary faunae of 

 Europe and the present molluscan faunas of South Amer- 

 ica and the Caribbean Sea. The Parana Formation is 

 in open contrast to the foregoing marine invasions of 

 Patagonia; and thus is afforded an exact proof that 

 diastrophic events of special importance took place in the 

 period between the Patagonian and Parana-Formation. 

 We may draw the inference that the peculiarity of the 

 fauna of the Patagonian Beds and its Australo-Ant'arctic 

 origin have been caused by restriction towards the north, 

 by a barrier like the "Archhelenis" of H. v. Ihering, 

 which separated the South Atlantic basin from the north- 

 ern marine provinces, and made impossible a free circu- 

 lation of streams and currents between this basin and 

 "Thetys." 



Presumably two facts explain the approximate form 

 and location of the barrier in question. First, the older 

 transgressions were in the strict sense of the word 

 limited to Patagonia ; and while the old mass in the socle 

 of the Sierras of Buenos Aires formed the northern limit 

 of the corresponding epicontinental seas, the Parana 

 Formation represents the only transgression that passed 

 over this limit, invading the mouth of the La Plata River 

 and advancing far to the north into the region of the 



33 Die Molluskenfauna und das Alter der Parana-Stufe, N. Jahrb. Min., 

 Beil.-Bd., 14, 1901. 



