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UNITED STATES NATIONAL MTJSETJM BULLETIN 215 



this lowermost faunal zone, and restricted to it, are 

 Glohorotalia compressa, Globigerinoides daubjergensis 

 and Chiloguemhelina morsei. C. midwayensis appears 

 in the upper part of the zone. 



The Landenian stage (upper Paleocene) contains a 

 Globigerina-keeled Globorotalia assemblage, and is typi- 

 fied by the species Globorotalia angulata. Species 

 typical of the angulata zone, which range almost 

 throughout its extent include Globorotalia angulata, 

 G. aequa, G. elongata and G. pseudomenardii, in addition 

 to the longer ranging G. perclara and Globigerina trilocu- 

 linoides. The angulata zone may be further subdivided 

 into subzones, the oldest of which is characterized by 

 Globorotalia pseudobulloides. This species first ap- 

 peared in the late Danian, but does not range above 

 this lower subzone of the Landenian. In addition to 

 the continuance of Globorotalia pseudobulloides and and 

 Globigerina triloculinoides, the subzone notes the first 

 appearance of Globorotalia angulata, elongata, pseudo- 

 menardii (all first appearing in the Matthews Landing 

 marl in the Alabama section), and G. aequa, reissi, 

 and irrorata (all appearing first in the Coal Bluff). 

 The angulata zone thus represents the beginning of the 

 group of keeled Globorotalia which become increasingly 

 numerous in later strata. 



The upper subzone of the Paleocene is commonly 

 referred to as the Globorotalia velascoensis zone, and is 

 characterized by that very angular and ornate species, 

 and the similar G. acuta. The typical velascoensis does 

 not range far north of its type region in Mexico, al- 

 though it does occur in Trinidad. In the Atlantic and 

 Gulf Coastal States it is replaced by the similar G. acuta, 

 which has been considered by some to be merely a 

 subspecies of G. velascoensis. In the region here studied 

 the faunal subzone is perhaps better typified by Glo- 

 bigerina spiralis, which ranges throughout the subzone. 



The Hornerstown formation is somewhat transitional 

 between the mid-Paleocene pseudobulloides subzone 

 and the upper Paleocene velascoensis-spiralis subzone. 

 Globorotalia pseudobulloides, compressa, and varianta 

 have disappeared, as have Chiloguembelina morsei, and 

 midwayensis. The species Chiloguembelina crinita, 

 Globigerina spiralis, and Globorotalia angulata, aequa, 

 and convexa have taken their place. However, the 

 G. acuta-velascoensis group, G. pseudoscitula, occlusa, 

 and Globigerina mckannai do not appear until after the 

 close of Hornerstown time. These species all are 

 present in the upper Velasco, Salt Mountain, Aquia, 

 and Vincentown formations, which thus are closely 

 related faunally. 



The lowermost Eocene (Ypresian) typically contains 

 a Globigerina-Globorotalia-Truncorotaloides assemblage. 

 In the Gulf and Atlantic coastal region here studied, 

 the lower Eocene is in many places represented by 

 nonmarine sediments, and the only fossUiferous mate- 

 rial used in the present study is that of the Nanafalia 

 formation of Alabama. It contains 17 species of 

 planktonic Foraminifera, some of which are holdovers 



from the upper Paleocene, but many of the most 

 typical Landenian species are absent. The close of 

 the Paleocene was marked by the disappearance of 

 Globigerina triloculinoides (it is replaced in many 

 regions by the similar G. linaperta, which is possibly 

 a derivative), mckannai, and spiralis, and Globorotalia 

 velascoensis, acuta, angulata, occlusa, and pseudoscitula. 

 The lower Eocene is characterized by the appearance 

 of Globorotalia rex (elsewhere also considered a zone 

 fossil for the Ypresian) and G. pseudotopUensis. The 

 Landenian, in more offshore marine sections, is also 

 recognized by the first appearance of the genus Trun- 

 corotaloides, which resembles a sharply angled Glo- 

 borotalia, but with supplementary apertm-es on the 

 spiral side. True Truncorotaloides has not yet been 

 observed in the Nanafalia, although the species, 

 Globorotalia pseudotopUensis Subbotina, is similar to 

 those which elsewhere did develop the supplementary 

 apertures. 



Summary 



The Danian stage of the lower Paleocene {compressa- 

 daubjergensis faunal zone of the Globigerina assemblage) 

 is represented by the lower Velasco formation of Mexico ; 

 the Kincaid and Wills Point formations, Midway group 

 of Texas; the Pine Barren and McBryde members of 

 the Clayton formation, lower part of the Midway 

 group of Alabama, and the Brightseat formation of 

 Maryland (text-fig. 28). 



The lower Landenian stage (Thanetian substage), 

 or middle Paleocene {angulata faunal zone, pseudo- 

 bulloides subzone of the Globorotalia assemblage), is 

 not represented at the sm-face in Texas, Maryland, 

 Virginia, or New Jersey. In Alabama it consists of 

 the Porters Creek clay and Naheola formation, the 

 upper part of the Midway group as previously 

 recognized. 



The upper Landenian stage (Sparnacian substage) 

 or upper Paleocene {angulata faunal zone, velascoensis- 

 spiralis subzone) represents the most controversial 

 part of the section. On the basis of the placement 

 elsewhere of the Globorotalia velascoensis zone as the 

 uppermost Paleocene, and in view of the gxeater 

 faunal break above than below this zone, it is here 

 regarded as upper Paleocene. This zone includes the 

 upper Velasco formation of Mexico, the Salt Mountain 

 limestone of Alabama (which is thus shown to be older 

 rather than yoimger than the Nanafalia formation 

 of the Wilcox group, and is here included as the upper 

 formation in the Midway group although younger 

 than the outcropping Midway of Texas), the Aquia 

 formation of Maryland and Virginia, and the Horners- 

 town and Vincentown formation of New Jersey. 



The lower Eocene (Ypresian stage) is mostly repre- 

 sented by nonmarine sediments in this region, marine 

 strata studied including only the Nanafalia formation 

 of Alabama, which represents the rex faunal zone of 

 the Truncorotaloides assemblage. 



