Paper No. 41-9
Presentation Time: 9:00 AM-5:30 PM
FIELD RELATIONSHIPS THROUGHOUT THE SOUTHERN DEATH VALLEY REGION OF CA REQUIRE THE HORSE THIEF SPRING FORMATION TO BE OLDER THAN THE 1.1 GA CRYSTAL SPRING DIABASE
Mahon et al (2014) renamed the upper member of the Mesoproterozoic Crystal Spring Formation as the Horse Thief Spring Formation (HTS), claiming its age to be <787 Ma on the basis of a few detrital zircons. This prompted a fresh look at the field relationships of the HTS and the Crystal Spring diabase because of the importance of their ages in deciphering the history of the Rodinia supercontinent (Calzia et al, 2015). We verify that throughout the region these diabase sills produced metamorphic aureoles in the HTS where they intruded adjacent to or into it. Inclusions of shale, siltstone and carbonate fragments from the HTS, sometimes folded, dismembered and/or clearly having mixed with the diabase magma, are widespread. Chilled diabase contacts are present where the proposed HTS age requires an unconformity. In the Jupiter Hill area of the northeastern Kingston Range, ~8 km east of the HTS type locality, a sill which intruded the HTS, picking up numerous HTS inclusions in the process, has a baddeleyite age of 1.1 Ga (Rämö et al, 2016) in agreement with the 1.1 Ga age for a sill in the northwest Kingston Range. The Saratoga Springs sill (1.07 Ga age) underlies the HTS reference section and detrital zircon sample location of Mahon et al. Apophyses from this sill occur in the conglomerate at the base of the HTS, and its contact metamorphic aureole extends into the HTS. In the southeastern Panamint Range, the Timmy deposit has a dramatic 450 m long and 30 m thick finger of HTS extending into a body of diabase. This and additional evidence that the HTS must be older than 1.1 Ga is documented with GPS-located photographs, maps, and a regional fence diagram summarizing the Mesoproterozoic stratigraphy.