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SDAG Monthly Meeting - VIRTUAL
Wednesday - September 29, 2021

Location: Your house, in front of your computer

6:30pm - get logged in, Happy Hour
7:00pm - Meeting begins

Join Zoom meeting from PC, Mac, Linux, iOS or Android:
Meeting ID: 857 9818 4239
Passcode: 461844

happy hour

Menu: What's in your fridge?

Cost: Free - BYO food and drinks.
If you are a current SDAG member and are not getting e-mail announcements,
make sure the SDAG secretary has your correct e-mail address.

6:00pm -

"Evidence of the Cretaceous-Paleogene Impact in California"

Speaker: Larry Busch

Lawrence Busch, California Professional Geologist PG - lic. no. 6440 (1995)

Empirical evidence and modeling indicate that the following events occurred as a result of the K-Pg impact at Chicxulub, Mexico: Impact blast, ejecta fallout, tsunami sequences, acidic aerosol generation and rain-out. We theorize that evidence of these events is preserved in the sedimentary record in California.

Paired clay-rich "ejecta" and Iridium-rich "fireball" layers occur globally. Impact-tsunami deposits are documented in the Gulf of Mexico. Elsewhere, tsunamis would likely be generated by seismically induced submarine landslides (Atlantic and Pacific coasts), and possibly by antipodal geoid displacement (southeast Asia).

Researchers have quantified a volumetric-range for acidic aerosols generated by the K-Pg impact into Yucatan's anhydrite target rocks. The estimated volume of acid is deemed sufficient to have produced, via enhanced weathering, the "spike" in sea-water strontium isotope values across the K-Pg boundary. These acidic solutions would likely reside in basins and lagoons until neutralized.

In California (and elsewhere), Paleocene rocks are characterized by kaolinite. Examples include: the Paleocene Simi Conglomerate, Silverado, and Goler Formations; and basal units of the "Eocene" Ione, Walker, and Maniobra Formations. Features common to these formations include laterization, pisolitic claystone, kaolinitized sediment and basement (saprolite), and lignite.

The classical interpretation is that these lateritic "paleosols" result from an extended period of weathering in a warm, humid environment. However, the laterite-bearing Silverado Formation and Simi Conglomerate are bracketed between Danian and Maastrichtian marine strata, which suggests a period of lowered sea level - and a cooler, drier climate.

We propose a model in which the observed intensive corrosion and kaolinitization of sediment and basement resulted when impact-generated acidic solutions collected in and saturated sediment-filled fluvial channels, basins, and lagoonal environments.

In this model, economic clay deposits in the Alberhill area represent sediment and basement variably altered by ponded acidic run-off. The Claymont Clay Bed, which consists exclusively of kaolinite and angular sub-mm quartz, may represent a deposit from a down-range ray of the clay-rich K-Pg impact "ejecta layer."

1998-2018, Engineering Geologist - California Geological Survey: Under the Surface Mining and Reclamation Act (SMARA), researched and produced Mineral Land Classification reports (Mineral Resource Evaluations) for use by the public, local and regional agencies for land use planning purposes. Regional Geologic Mapping Program, co-produced the Ramona and San Pasqual 7.5' minute geologic maps. (Retired 2018)

1996-1997, Engineering Geologist - North Coast Regional Water Quality Control Board (Santa Rosa, CA): Managed caseload of sites with histories of chlorinated solvent and/or severe hydrocarbon contamination. NPL: Performed preliminary assessment and site investigation evaluating and testing for chromium-, copper-, and pentachloraphenol-based wood preservative contamination on a site impacted by the 1964 Crescent City Tsunami with eventual placement on the National Priority List.

1991-1995, Geologist, - Environmental, Geotechnical Consulting (San Diego): Solid Waste Assessment Testing, Subsurface hydrocarbon and chlorinated solvent assessment, characterization, and remediation. Geologic and Geotechnical investigations.

1990 - USGS, Visiting Scientist: Geophysical survey for the collection of multichannel seismic reflection, gravity, and seismic refraction data over the California Continental Borderland aboard the research vessel R/V S.P. Lee.

1990 - Pro Bono Geologic Consulting: Provided pro bono geological services to opponents of the Blue Canyon proposed North San Diego County landfill project. Successfully challenged accuracy and adequacy of the EIR/EIS regarding evidence of faulting within the landfill footprint. Provided written reports, testimony in a workshop before the SDRWQCB, and testimony in public hearings before the San Diego County Planning Commission and Board of Supervisors.

1988-1989 - Exploration geologist, St. Joe/Bond Gold Exploration: Managed regional stream sediment sampling program for gold mineralization with projects in California, Arizona, Nevada, Oregon, Montana, Colorado, and New Mexico.

1987 - Exploration Geologist, Westmont Mining Company: Gold exploration activities/drilling, Mt. Hamilton, White Pine County, Nevada.

Upcoming SDAG meetings - 2021

September 29: - Larry Busch - virtual

Meetings are usually scheduled for the 3rd Wednesday evening of the month. Meeting information on this website is normally updated the second week of the month.

Recordings of past meetings

9/29/2021: Larry Busch "Evidence of the Cretaceous-Paleogene Impact in California"
Passcode: 18U&v.pb

8/18/2021: Markes E. Johnson "Rhyolite Domes and Subsequent Offlap of Pliocene Limestone on Volcanic Islets at San Basilio (Baja California Sur, Mexico)"
Passcode: uwgF$X6p

7/21/2021: Student Scholarship Presentations "Analysis of Arctic Beaufort Sea Cores..." and "Lake Cahuilla and its effects on the SSAF system"
Passcode: 2M1LkG!C

5//2021: Hans Janzon "Nuclear Waste Disposal in Rock: Sweden and the US"
Passcode: AQpMR@4#

4/21/2021: EERI Speakers: 1) Prof. Thomas Rockwell (San Diego State University), 2) Timothy Dawson (California Geological Survey), 3) Michael DeFrisco (California Geological Survey), 4) Discussion Q&A. Moderator: Dr. Jorge Meneses

3/17/2021: Barry Keller "Sediment Transport in the San Francisco Bay Estuarine System"
Passcode: 5+Y5m?h@

2/17/2021: Dr. Norrie Robbins "Origin of Our Redbeds Pigmentation by Chembiotic Oxidation of Detrital Magnetite in Red Brown Pleistocene Terrace Sandstones, San Diego, CA."
Passcode: ^DK2UW0=

1/20/2021: W. Paul Burgess, M.S., P.G. California Geological Survey "Shallow landslide and debris flow activity in San Diego County, early April, 2020"
Note: ZOOM speaker's presentation begins at time 1:44:00.

12/16/2020: Dr. Tom Demere of the SDNHM "Suprise Talk!!."
Passcode: b.Wh7f&&
Note: ZOOM speaker's presentation begins at time 1:10:00.

If you have any information, announcements, ads or suggestions for an upcoming newsletter, please submit it to 2021 SDAG Secretary. Any news regarding upcoming events that may be of interest to the Association or news of your business can be submitted. The submittal deadline for the next SDAG newsletter is the last Friday of the month.
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