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Discovery Timeline

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Retired PaleoServices Field Paleontologist Richard Cerutti discovers the site. Curator of Paleontology and Director of PaleoServices Dr. Tom Deméré and PaleoServices Field Paleontologist Brad Riney meet with Richard at the site to formulate plan for excavation of the fossils.

November 16, 1992

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Formal excavation of the site begins.

November 17, 1992

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Caltrans archaeologists visit the Cerutti Mastodon Site and help screen sediment from disturbed area.

November 18, 1992

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Steve’s Horse Quarry discovered and excavated over next nine days.

November 19, 1992

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Dr. Tom Deméré begins videotaping/documenting the Cerutti Mastodon Site.

December 3, 1992

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Paleontologist Dr. Larry Agenbroad visits the Cerutti Mastodon Site for the first time.

December 19, 1992

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SDSU Geologist Dr. Pat Abbott visits the Cerutti Mastodon Site for the first time.

December 24, 1992

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Dr. Larry Agenbroad and Paleontologist Dr. Jim Mead join the excavation team for one week of field work.

December 28, 1992

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Dr. Tom Deméré videotapes the Cerutti Mastodon Site.

December 29, 1992

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Former PaleoServices Field Paleontologist Steve Walsh mentions discussion with Larry and Jim about a Sangamonian versus Wisconsinian age for the Cerutti Mastodon Site.

December 31, 1992

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Dr. Tom Deméré videotapes the Cerutti Mastodon Site.

January 4, 1993

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National Geographic Society awards emergency grant of $14,038 to support field work and travel.

January 14, 1993

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Dr. Larry Agenbroad returns to San Diego for two-day visit.

January 23, 1993

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Dr. Tom Deméré videotapes the Cerutti Mastodon Site.

January 25, 1993

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SDSU Geologist Dr. Tom Rockwell visits the Site and suggest an age of 300 ka +/- one interglacial (i.e., 200 ka to 400 ka) based on elevation, caliche volume, and degree of modern soil development.

January 27, 1993

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CM-423 cobble found in Unit G-5 at the Cerutti Mastodon Site.

March 22, 1993

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Dire wolf skeleton discovered.

April 5, 1993

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Column sample of quarry stratigraphy jacketed in northwest corner of Unit F-5 at the Cerutti Mastodon Site.

April 21, 1993

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Steve Walsh collects OSL samples from north wall of Unit B-6; last day of field work at the Cerutti Mastodon Site.

April 27, 1993

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Cerutti Mastodon Site buried by bulldozer.

April 28, 1993

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Richard KU (USC) calls Dr. Tom Deméré with preliminary radiometric results and date of ~190 ka on caliche sample.

December 29, 1993

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USC Geologist Dr. Richard Ku sends letter report with radiometric (U-Th) dating results.

January 7, 1994

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State Route 54 Paleontological Mitigation Report submitted to the California Department of Transportation (Caltrans).

March 20, 1995

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Archaeologists Dr. Steve Holen and Kathleen Holen first research visit to San Diego Natural History Museum to examine the fossils and artifacts salvaged from the Cerutti Mastodon Site.

February 2, 2008

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Conference on Cerutti Mastodon Site held at San Diego Natural History Museum. Attendees included Dr. Tom Deméré, Richard Cerutti, Dr. Steve Holen, Kathleen Holen, Dr. Dan Fisher (paleontologist and mastodon expert), Dr. Tom Stafford (archaeologist and dating expert), George Jefferson (paleontologist and Pleistocene expert), Dr. Steve Forman (OSL dating expert), Dr. Pat Abbott, and Dr. Mark Becker (archaeologist and lithic expert).

May 28-29, 2009

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Trench excavated into the south side of the sound berm directly opposite the Cerutti Mastodon Site to collect fresh sediment samples for OSL dating.

May 28, 2009

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First Cerutti Mastodon Site samples sent to Dr. James Paces, geologist and geochronologist at the U.S. Geological Survey.

May 16, 2011

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Initial radiometric (U-Th) dating results reported to the Cerutti Mastodon Team.

February 18, 2012

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Dr. Jim Paces and Dr. Steve Holen visit the San Diego Natural History Museum to identify additional samples for dating.

April 2012

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Two Cerutti Mastodon Site rock specimens (CM-254, 383) sent to Australia for use-wear and residue analysis. Initial contact with Archaeologist Dr. Richard Fullagar.

October 5, 2012

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Dr. Jim Paces prepares multiple specimens and performs digestions, chemical separations and purifications, and completes isotope analyses on nearly 100 individual subsamples.

July 2012 to December 2014

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Dr. Jim Paces compiles and evaluates all data using newly published numerical age models that consider diffusion, absorption, and decay of U in bone.

January to April 2015

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Geoarchaeologist and Soil Scientist Dr. Jared Beeton visits the San Diego Natural History Museum for first time to examine Cerutti Mastodon Site collection and obtain sediment samples and soil descriptions.

February 2015

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Final age determination for the Cerutti Mastodon bones of 130,700 ±9,400 years is reported to the Cerutti Mastodon Team.

May 2015

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Initial submission of Cerutti Mastodon Site manuscript submitted to the prestigious science journal Nature.

March 17, 2016

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Formal acceptance of Cerutti Mastodon Site manuscript by the science journal Nature.

March 13, 2017