Английская Википедия:Beaverdam Formation (Delmarva)
The Beaverdam Formation is an upper Pliocene geologic formation on the Delmarva Peninsula in southern Delaware and eastern Maryland.[1][2] It is the largest major surficial layer on the Delmarva Peninsula and has a lower stream-deposited unit and an upper estuarine unit. These units may represent a cycle of regression and transgression.[3] The Beaverdam Formation is heterogeneous and ranges from very coarse sand with pebbles to silty clay.[1] It unconformably overlies the Manokin or St. Mary's formations and it is up to 75-100 feet thick.[4]
The extent of the Beaverdam Formation is recognized from Delmar to the west and to Milford and Georgetown to the northeast.[2]
History
The Beaverdam Formation was originally named the Beaverdam Sand when it was recognized in Wicomico County, Maryland in 1955 by William C. Rasmussen and Turbit H. Slaughter.[5][6] The name comes from Beaverdam Creek, the east branch of the Wicomico River.[5] The Beaverdam Sand was renamed the Beaverdam Formation and given an expanded lithologic definition by Kelvin W. Ramsey and William S. Schenck in 1990.[7][6]
Microflora
The lower Beaverdam Formation is characterized by a Quercus-Carya pollen assemblage, very few non-arboreal pollen, and the exotic constituents Pterocarya and Sciadopitys. The upper Beaverdam has a very high non-arboreal pollen concentration, and the sole exotic constituent is Pterocarya. Other significant taxa include Cupuliferoidaepollenites fallax, Tricolporopollenites edmundii, and Tsuga diversifolia-type. The pollen assemblage of the lower Beaverdam is similar to that of the Bethany Formation in Delaware, the Brandywine Formation in Maryland, and the Eastover Formation in Virginia; and the pollen assemblage of the upper Beaverdam is similar to that of the Bacons Castle Formation in Virginia.[2]
Шаблон:Lithostratigraphy of the southeastern Delaware Neogene
See also
References
External links
- ↑ 1,0 1,1 Шаблон:Cite map
- ↑ 2,0 2,1 2,2 Ошибка цитирования Неверный тег
<ref>; для сносокagesне указан текст - ↑ Шаблон:Cite book
- ↑ Шаблон:Cite map
- ↑ 5,0 5,1 Ошибка цитирования Неверный тег
<ref>; для сносокmd-1955не указан текст - ↑ 6,0 6,1 Шаблон:Cite report
- ↑ Шаблон:Cite map
