37-17 Exploration into the Upper Johnnie Formation Regarding Correlation with the Acraman Impact

Session: Geoscience Research Poster Showcase by 2YC and 4YCU Undergraduate Students

Poster Booth No.: 140

Presenting Author:

Billyjack Jory

Authors:

Nevarez, Camila¹, Mack, Caroline², Liebl, Claus³, Alvarez, Itzel⁴, Boosinger, Thistle⁵, Rodriguez, Brandon⁶, Jory, Billyjack⁷

(1) Geosciences Department, Pasadena City College, Pasadena, CA, USA, (2) Geosciences Department, Pasadena City College, Pasadena, CA, USA, (3) Geosciences Department, Pasadena City College, Pasadena, CA, USA, (4) Geosciences Department, Pasadena City College, Pasadena, CA, USA, (5) Geosciences Department, Pasadena City College, Pasadena, CA, USA, (6) Center for Collaborative Education, Boston, MA, USA, (7) Department of Geography, University of California Los Angeles, Los Angeles, CA, USA,

Abstract:

Recent analysis of the Rainstorm Member of the Johnnie Formation (approx. 585-579 Ma) (Witkosky and Wernicke, 2018) conducted near the Western Talc Mine southeast of Death Valley, CA, and in the Spring Mountains, NV, reveals distinct crossbedding trends within the oolite and underlying quartzite strata. When quartzite bedding is adjusted to paleohorizontal, the foresets trend in a southeastern strike–at an average of 140.6° azimuth ±24.3॰, and dip average of 13.7° ±7.18॰. When oolite bedding is adjusted to paleohorizontal, crossbeds within dip either to the west or east at an average of 9.6°. These beds strike at a respective average of 196° azimuth (south), or 357.4° azimuth (north), though more specific measurements and sampling of interbed structures within the oolite is necessary to perform more comprehensive statistical analysis and hypothesize details of deposition, which could be influenced by tsunamigenic wave action indicated by differences in the attitude of the quartzite and oolite.

 

This Ediacaran continental shelf region is an area of interest, as recent work has drawn a possible temporal correlation with its time of deposition and that of the Acraman impact in South Australia (Rodriguez et al. 2025).  We aim to further analyze the Upper Johnnie Formation and establish an understanding of shoreline orientation and aquatic conditions to explore possible indicators of tsunamigenic wave action near the high Iridium concentration region measured along the oolite marker bed. Existing interpretations of the paleoshoreline direction this area range from east-west (e.g. Bergmann et al. 2011) to more north-south trends (e.g. Stewart, 1970). The variation between these interpretations is a key point of interest to future work because of their near 90° difference. Future work will collect additional measurements of correlating strata in an expanded region of localities, with an emphasis on measuring multidirectional oolite crossbedding and herringbone quartzite foresets in order to build a clearer model of the paleo-flow and shoreline orientation of the western margin of Laurentia at the time of the Acraman impact.

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