PHYSICAL CONDITIONS AND AGE INDICATED BV FLORA OF ALL'M BLUFF FORMATION. 



45 



soa due to the elevation of the PjTenees and the 

 begiiniing of Alpine orogenesis. Marine waters 

 invadetl the marginal coasts in Aquitaine, the 

 Gironde, and Provence, in southern Spain, in 

 Italy, and at various points on the south side 

 of the eastern Alps; but the great bulk of the 

 Atjuitanian sediments are those of lakes, 

 swamps, and lagoons, with lignites and abun- 

 dant and widespread mammals and plants. 

 In Aquitaine the Tongrian is said to grade 

 imperceptibly into the Aquitanian both litho- 

 logically and faunally, and the latter passes 

 into the BunUgalian in the same gradual man- 

 ner. The floras of the Aquitanian arc like- 

 wise transitional in character between Oligo- 

 cene and Miocene. The marine faunas, how- 

 ever, are said by Haug to contain only 4 per 

 cent of Oligocene species and many Miocene 

 species, but the foraminiferal genus Lepido- 

 cyclina passes without modification from the 

 Chattian into the Aquitanian. The Aqui- 

 tanian has long been considered the uppermost 

 stage of the Oligocene, although many paleon- 

 tologists have pointed out the resemblances 

 between the upper Aquitanian floras and 

 faunas and those of the Burdigalian. In recent 

 years, under the leadership of DoUfus and other 

 French students, the Acpiitanian has been made 

 the basal stage of the Miocene, although the 

 question of its reference to the Oligocene or 

 Miocene is vigorously disputed. 



The Burdigahan (Deperet, 1892) is closely 

 related to the Aquitanian both faunally and 

 florally. The marine faunas as well as the ter- 

 restrial floras are said to indicate a shght 

 lowering of temperatures since Aquitanian 

 time. Tectonic changes had caused the dis- 

 appearance of the broad lakes of the Aqui- 

 tanian, and the Burdigalian materials comprise 

 marine sediments on the southern and west- 

 ern borders of the continent and a series of 

 river, flood-plain, and swamp deposits (brown 

 coal) in the region extending from France to 

 Bohemia. 



It can not be said that the Alum Bluff flora 

 offere conclusive evidence for detailed correla- 

 tion, as it is too small. .Ul but two of the 

 species are new and offer only indirect evi- 

 dence. Of these new species the Ulmus is 

 very similar to Ulmus longifolia Unger, of the 

 Aquitanian of Bohemia, Germany, Styria, 

 and France, and the Sapotacites is most 

 like Sapotacites {Clirysophi/llum) sagorianum, 

 from tlie Aquitanian of Sagor, in Camiola, 



described by Ettingshausen. The two species 

 with an outside chstribution, Cinnainomum 

 sclieuchztri and Diospi/ros hrachysepala, have 

 both been identified in beds from a great va- 

 riet}- of horizons in Europe. Although many 

 of these identifications are of doubtful value, 

 both species had a wid<^ range, geographic as 

 well as geologic. Th(* original descriptions of 

 both, by Alexander Braun, were based on 

 material from the Tortonian of Oeningen in 

 Baden. The two species are typically Oligocene- 

 Miocene forms and both ani common and cliar- 

 acteristic in the A(|uitanian and Burdigahan of 

 Europe. 



It is thus apparent that the ^Vlum Bluff flora 

 can be considered either Aquitanian or Burdi- 

 galian, with a slight preponderance of the evi- 

 dence in favor of the Aquitanian. Maury ' on 

 the evidence of the molluscan fauna correlated 

 the Chipola marl with the Aquitanian and con- 

 sidered the Oak Grove fauna, as well as that 

 of the sands at Alum Bluff above the Chipola, 

 as ''transitional" between Aquitanian and 

 Miocene. If subsecjuent paleozoologic studies 

 corroborate Maury's work, there will be sub- 

 stantial agreement between the floral and 

 faunal evidence. 



If the Alum Bluff formation is of Aqui- 

 tanian or Burdigalian age — and one or the 

 other alternative seems certain — the more or 

 less academic question is raised whether it 

 shall be classed as Ohgocene or Miocene. 



Since the proposal of the term Oligocene by 

 Beyrich in 1854 many have questioned its 

 utihty or ultimate survival. Certainly there is 

 but slight structural (diastrophic) evidence for 

 placing the Oligocene-Miocene boundary in 

 Europe between the Aquitanian and Burdi- 

 gahan, and the marine faunas as well as the 

 terrestrial floras and faunas show a gradual 

 transition from the one stage to the other, so 

 that the French paleontologists will probably 

 be followed in tlieir contention that the Aqui- 

 tanian should be placed in the Miocene. 



In considering the American application of 

 the term Ohgocene, it may be noted that tliero 

 appears to have been continui)us and uninter- 

 rupted sedimentation in the Florida area from 

 the deposition of tlu^ uiulerlying Chattahoochee 

 formation into Alum Bluff time. Tliere also 

 seems to have been a succession of minor earth 

 movements during this period, and there was 

 a greater influx of terrigenous materials into 



' Maury, C. O., Bull. Am. Paleontology No. 15, 1902, 



