Also known as Near Hawarden

Where: Sioux County County, Iowa (43.1° N, 96.4° W: paleocoordinates 29.0° S, 40.1° W)

• coordinate estimated from map

When: Givetian to Givetian (387.7 - 372.2 Ma)

• "a thin, previously unknown deposit of silty shales above a thin sandstone overlying Precambrian gneissic basement and overlain unconformably by the Nishnabotna Member of the Cretaceous Dakota Formation (Ludvigson and Bunker, 1979)."

•“The spores recovered from the Hawarden core are difficult to examine in detail because of the presence of amorphous kerogen in the samples but a Middle or Late Devonian age is suspected (Ravn, personal commun.). A similar unit of brown, sandy, organic-rich shale was encountered approximately 20 km to the east, though not cored, in well D-44, Iowa Geological Survey, Boyden, Sioux County, Iowa (NE/4, SE/4, NE/4 sec. 9, T96N, R44W, Sioux Co.) (Figure 2). Here the shale overlies Cambrian dolomite, probably the Upper Cambrian Bonneterre Formation (Witzke, personal commun.). […] the rocks probably represent the same strati-graphic unit. Palynomorphs present in well D-44, all trilete spores, are relatively free of kerogen and include, most abundantly, Geminospora cf. G. svalbardiae (Vigran, 1964), but also Ver-rucosisporites premnus Richardson, 1965, Dictyotriletes sp., Samarisporites sp., and Convolutispora sp. […] The entire floral assemblage thus seems to indicate a Middle to early Late Devonian, probably Givetian or Frasnian, age (Ravn, personal commun.).”

Environment/lithology: fluvial; pyritic, brown, silty, sandy shale and siltstone

Size class: macrofossils

Collection methods: chemical

• "repeatedly processed in household bleach to oxidize the organic shale binder, the residue screened and dried, and systematically picked."

Primary reference: G. W. Storrs. 1987. An ichthyofauna from the subsurface Devonian of northwestern Iowa and its biostratigraphic and paleoecologic significance. Journal of Paleontology 61(2):363-374 [E. Dunne/S. Fasey]more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 226053: authorized by Emma Dunne, entered by Sophie Fasey on 13.06.2022

Creative Commons license: CC BY (attribution)