Douglas - Hypervelocity Impact Crater

Alternate Names
Local Language
Coordinates 42° 40' 48" N; 105° 28' 12" W
Notes
  1. More than 40 circular to ellipsoidal craters are located within a 7.5 km strewn field on the NE side of the Sheep Mountain anticline near Douglas, Wyoming.
Country United States of America
Region Wyoming
Date Confirmed 2018
Notes
  1. Confirmed based on the presence of PDFs in quartz (Kenkmann et al., 2018). Also see more recent reference, Shulze et al., 2019, who describe PDF's and PF's in quartz (LMI 2019 abstract).
Buried? No
Notes
  1. However, there may be craters in the NE part of the strewn field that may be buried beneath younger strata (Kenkmann et al., 2018).
Drilled? No
Target Type Sedimentary
Notes
  1. Craters are exposed within Lower Permian Casper Formation consisting of quartz-cemented sandstone (Kenkmann et al., 2018).
Sub-Type Sandstone
Apparent Crater Diameter (km) Unknown
Age (Ma) ~280
Notes :
  1. Based on stratigraphy, the impact age of strewn field is inferred to have occurred after the deposition of the Casper Formation and before the Goose Egg Formation Opeche Member at ~280 Ma (Kenkmann et al., 2018).

Method :
  1. Stratigraphy
Impactor Type Unknown

Advanced Data Fields

Notes

Erosion
3
  1. Erosion varies among craters within this strewn field from preserved ejecta to crater cavity mostly eroded so this value reflects an average erosional value (Kenkmann et al., 2018).
Final Rim Diameter
73 m
Apparent Rim Diameter
Unknown
  1. 8 confirmed craters and 43 circular structures total have been identified within the field. Confirmed craters are SM-1 (60 x 41 m), SM-3 (17 m), SM-4 (12 x 10 m), SM-9 (20 m), SM-34 (73 x 51 m), SM-36 (21 m), SM-78 (14 m), and SM-80 (62 x 56 m); SM refers to the location of craters at Sheep Mountain (Kenkmann et al., 2018). Rim to rim diameter of confirmed and possible craters range from 10 m to 82 m (Kenkmann et al., 2018). Also see Schulze et al. 2019 - LMI abstract.
Rim Reliability Index
1
  1. Simple impact crater.
Crater Morphology
Simple
Central Uplift Diameter
km
Central Uplift Height
Unknown
Uplift Reliability Index
2
Structural Uplift
Unknown
Thickness of Seds
Target Age
Palaeozoic
Marine
No
Impactor Type
Other Shock Metamorphism
No
Shatter Cones
No
Planar Fractures
Yes
  1. Planar fractures were identified in quartz grains from two craters. PF lamellae decorated with fluid inclusions (Kenkmann et al., 2018).
Planar Deformation Features
Yes
  1. PDFs were identified in quartz grains from 9 craters. PDF lamellae decorated with fluid inclusions (Kenkmann et al., 2018).
Diaplectic Glass
No
Coesite
No
Stisovite
No
Crater Fill
LB
  1. Monomict brecciation is found along the raised rim of several craters. Relics of ejecta blankets at some craters is preserved. Several crates show dyke injections along the rim and inner crater slopes or within the crater cavity (Kenkmann et al., 2018).
Proximal Ejecta
Yes
Distal Ejecta
Dykes
Yes
Volume of Melt
Depth of Melting