John A. Chamberlain Jr.
Philip W. Stoffer
Paula Messina
Patricia Jannett
Dennis O. Terry Jr.
2001
<p><span>A distinctive zone of disrupted strata, which we interpret as a distal manifestation of the end-Cretaceous Chicxulub impact event, occurs over 300 km</span><sup>2</sup><span> in southwestern South Dakota. This disrupted zone is within the Fox Hills Formation, ranges from 0.5 to 5 m in thickness, and contains large-scale slump-roll structures, clastic dikes, flame structures, and massive, homogenized beds. The zone is ∼0.5 m above a belemnite fauna Sr dated as 67.6 ± 0.5 Ma, contains scaphitid ammonites characteristic of the </span><i>Jeletzkytes nebrascensis</i><span> ammonite zone of the Fox Hills Formation, and is capped by a 0.5–4-cm-thick brownish-black mudstone that contains spherules. Pollen of the late Maastrichtian </span><i>Wodehouseia spinata</i><span> palynostratigraphic zone occurs immediately above and below the disrupted zone. The disrupted zone is overlain by an additional 25 m of marine Fox Hills Formation. These stratigraphic relationships suggest that the upper part of the Fox Hills Formation in this part of South Dakota is Paleocene; that the Western Interior Seaway was locally present well into the Paleocene; and that scaphitid ammonites may range the Cretaceous-Tertiary (K-T) boundary.</span></p>
application/pdf
10.1130/0091-7613(2001)029<1055:MCTBSI>2.0.CO;2
en
Geological Society of America
Marine Cretaceous-Tertiary boundary section in southwestern South Dakota
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