Early Cretaceous (Albian) spores and pollen from the Glen Rose Formation of Texas and their significance for correlation of the Potomac Group

ABSTRACT

Because the Gulf Coast Lower Cretaceous is dated by ammonites, it has great potential as a reference section for correlating continental sequences such as the Potomac Group and dating events in the rise of angiosperms. Middle Albian terrestrial palynofloras from Oklahoma have been described in detail, but the early Albian interval, represented in the Glen Rose Formation of Texas, is less well known. Samples from two localities on the Paluxy River, which correlate with horizons containing late early Albian ammonites, are dominated by Classopollis and Exesipollenites, but angiosperm pollen is the next most common terrestrial element, and there are several index spore species for Zone II in the Potomac Group. Among the angiosperms, reticulate monosulcates are most common and diverse, but there are also several tricolpate species. Stratigraphically important angiosperms include the Clavatipollenites rotundus group and reticulate tricolpates, which appear in the upper part of Potomac Zone I and the dated earliest Albian of England and Portugal. However, there are also tricolpates with striate-reticulate sculpture, a pollen type that is not known from upper Zone I but appears in the late early Albian of Portugal. This assemblage contrasts with floras from Potomac Zone II and the middle Albian (lower Fredericksburg Group) of Oklahoma, where tricolpates overtook monosulcate angiosperms in species diversity. These results confirm arguments based on the Portuguese section that there is a significant hiatus between Potomac Zones I and II, and that this gap is at least partly late early Albian. The dominance of Classopollis and Exesipollenites and the occurrence of isolated Northern Gondwanan elements (Sergipea, Tucanopollis) suggest that Texas lay in a transition zone between Southern Laurasia and the hotter and drier Northern Gondwana province, but regional studies are needed to disentangle geographic and climatic factors from effects of the lagoonal local environment.

KEYWORDS:

• Cretaceous
• Albian
• Texas
• palynology
• angiosperms
• stratigraphy
• Potomac

Acknowledgements

We thank Turkish Petroleum for funding, Phoebe Ayers for extensive help with literature research, Özge and Sinan Akyürek for photocopying the Beach thesis, Cynthia Looy and Diane Erwin for the use of facilities at the UCMP, the UC Berkeley Sedimentology Lab for sieving samples, Sandra Carlson and Isabel Montañez for comments on the MS thesis by ST on which this work is based, and Robert Scott for discussion of Gulf Coast Cretaceous stratigraphy.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Sinem Tanrikulu

SINEM TANRIKULU received a BSc from the Department of Geological Engineering at the Middle East Technical University in Ankara, Turkey, in 2011, and was awarded a government scholarship to conduct MSc studies abroad. In 2015 she earned her MSc in geology from the Department of Earth and Planetary Sciences at the University of California, Davis, under the supervision of James A. Doyle and Irina Delusina, for the study on Early Cretaceous spores and pollen of the Glen Rose Formation that forms the basis of this article. Currently she is working at Turkish Petroleum in Ankara and pursuing PhD studies at the Middle East Technical University on Silurian palynomorphs (spores, acritarchs and chitinozoans) of the Tauride Mountains.

James A. Doyle

JAMES A. DOYLE received his PhD at Harvard in 1970, working on angiosperm pollen of the Potomac Group and its evolutionary implications. As a postdoc at the Smithsonian Institution in 1971 and a faculty member at the University of Michigan until 1978, he extended this work to angiosperm leaf floras, in collaboration with Leo Hickey, and to early angiosperm pollen from Gabon and Congo, with palynologists at Elf-Aquitaine. He moved to the University of California, Davis, in 1978, officially retiring in 2013. In the 1980s his research emphasis shifted to phylogenetic analyses of living and fossil seed plants and basal angiosperms, particularly Annonaceae and Chloranthaceae. Recently he has been returning to his paleobotanical roots with analyses of the position of fossils in molecular phylogenies of living angiosperms and reassessment of Cretaceous stratigraphic problems.

Irina Delusina

IRINA DELUSINA is a project scientist in the Department of Earth and Planetary Sciences at the University of California, Davis. She graduated from St. Petersburg University, Russia, and completed her PhD at the Institute of Geology of the Estonian Academy of Sciences in 1989. She then received an Alexander von Humboldt-Stiftung postdoctoral fellowship to work at the University of Hohenheim, Germany. She is using palynology to reconstruct Quaternary paleoclimates in different regions of the world, including northwestern Russia, California, the Chukchi Sea and the Caribbean Basin, and she served as palynologist on a cruise to Baffin Bay to study the stratigraphy of Cretaceous sediments.