107-13 Detrital Zircon Geochronology of the Cenomanian Windrow Formation at Iron Hill, Northeast Iowa, USA

Session: Sedimentary Geology Division/SEPM Student Research Poster Competition: Dynamics of Stratigraphy and Sedimentation

Presenting Author:

Authors:

Abstract:

The Windrow Formation is a widely distributed Cenomanian conglomerate and sandstone that occurs in unglaciated areas of Wisconsin, Minnesota, Iowa and Illinois.  The Windrow Formation consists of the lower Iron Hill Member (Fe-rich residuum) and upper East Bluff/Ostrander Member (gravel, sand, and clay) and is roughly correlative to the Nishnabotna Member of the Dakota Formation in western Iowa.  At 1,345 ft (430 m), Iron Hill is the highest point in northeastern Iowa and is the type section for the Iron Hill Member of the Windrow Formation. At this locality, Cretaceous-aged strata unconformably overlie cherty massive dolomites of the Galena Group Dunleith Formation.  The irregular erosional surface shows abundant dissolution cavities filled with limonite concretions or cellular masses and red/white plastic clay with residual chert and carbonate clasts.  The Iron Hill Member attains a maximum thickness of 70 ft (22 m).  Here we present detrital zircon U-Pb data (n=225) from the Iron Hill Member at the old Waukon Iron Mine just north of Waukon, Iowa (43.303542, -91.460967).  Analyses were completed at the University of Arizona Laserchron Center.  The age spectrum has a prominent peak of ~1050 Ma, which we interpret to sourcing from Grenville (Ottawan Phase) orogen of the northern Appalachian Mountains.  Smaller populations of Taconic-Acadian (450 Ma age peak) and Pan-African (610 Ma age peak) and Pinware (1460 Ma age peak) also are present.  Our data is consistent with the data from correlative strata to the west and further supports the model of Cenomanian sediment sourcing from the northern Appalachian Mountains.  This long-standing, high topography shed sediment to the west from the late Mississippian through the early Cretaceous. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10291

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.