Abstract: 

The Sierra Nevada has played an important role in the history of paleoglaciology in the United States, and indeed globally.  The role of glaciation in shaping the range was discussed by J.D. Whitney, John Muir, and Joseph LeConte in the late 1860’s and the 1870’s.  Even at this early time, the evidence was abundant that the Sierra Nevada had been extensively glaciated in the not-too-distant geological past.

When Elliot Blackwelder in 1931 provided the first comprehensive description of the glacial history of the Sierra Nevada he recognized four glacial stages.  This was not because of widespread evidence for four advances, rather, it was because four stages were required by the prevailing paleoclimatic theory of his day.  In fact, while there is abundant evidence of the two most recent advances, that for Blackwelder’s two older stages is exceedingly fragmentary.  Blackwelder named the penultimate and the most recent glacial stages the ‘Tahoe’ and the ‘Tioga’, respectively.  Today, chronology provided mainly by cosmogenic nuclide accumulation dating, but supplemented by other methods, has demonstrated that the Tahoe is contemporaneous with the global glacial maximum of Marine Isotope Stage (MIS) 6 (~140 ka) and the Tioga with the maximum of MIS 2 (~20 ka).  Given that the severity of preceding glacial stages in the marine isotope record is very similar to these two stages, it seems highly likely that the Sierra Nevada over the past million years has undergone multiple glaciations of similar magnitude to the Tahoe and Tioga.  This is at least partially confirmed by geochemical evidence from a core in Owens Lake sediments that extends back to ~800 ka.  It shows multiple cycles of wet conditions very similar to the Tahoe and Tioga and dry conditions similar to the Holocene.  These cycles follow the same chronology as the Marine Isotope Stages.

The history of the deglaciation of the Sierra Nevada at the end of MIS 2 can be reconstructed in considerable detail, unlike previous advances and retreats for which the evidence has been destroyed by subsequent glacial erosion.  The evidence indicates that the glaciers reached a position close to that of the terminal moraine by 26 ka, well before the global Last Glacial Maximum at about 20 ka.  The terminal position was occupied from about 21 to 19 ka.  Between 19 and 16.7 ka the glaciers retreated far back in the range.  Between 16.7 and 16.2 ka they readvanced, eventually reaching about one-third of the glacial maximum extent.  At 16.2 ka they retreated very rapidly, deglaciating the Sierra Nevada, except perhaps for a few very small cirque glaciers.  There is no indication of subsequent glacial expansion until the diminutive Recess Peak advance between 14.0 and 12.5 ka. Whether this coincided with the quasi-global Younger Dryas event (12.9-11.6 ka) is uncertain.

During the early Holocene, even the tiny cirque glaciers apparently disappeared.  These re-formed at about 3 ka and advanced until the termination of the Little Ice Age at the end of the Nineteenth Century.  Today they are rapidly disappearing as Global Warming renders the Sierra Nevada unsuitable for glaciers.

In the end, the 74 people in attendance heard a presentation on the tephrochronology of the Monterey and Modelo Formations. Many of the samples were collected during grading operations here in Orange County. Hopefully, not too many people were disappointed and we will try and get Sue Hough at a future meeting to tell us about the Northridge earthquake.

McMichael, Ryan (CSUF – Undergraduate)

“Unveiling the Secrets of Marine Terrace Rings: A Window into Paleoenvironmental Change and Ecological Shifts”

Munoz, Jonathan (CSUF – Undergraduate)

“Uncovering Hidden Influence: Unconventional Non-Demographic Variables Shape Success and Close Educational Gaps in Introductory Geology”

Onderdonk, Nate (CSULB – Professor)

“Paleomagnetic directions and Argon dating of Miocene rocks show unusually rapid vertical-axis rotation on Santa Catalina Island, offshore southern California“

Ortega, Sonny (CSUF – Undergraduate)

“Assessing the role of wood fragments in the formation of calcite concretions of the Late Cretaceous Holz Shale, Santa Ana Mountains“

Ruiz, Roberto (CSUF – Undergraduate)

“Rancho Mission Viejo Riding Park Recharge System“

Scandore, Alex (CSULB – Undergraduate)

“Alteration and hydrothermal fluid provenance in the Lima Segment of the Peruvian Coastal Batholith”

Walters, Polito (CSULB)

“Hydrothermal Alteration Related to the Brittle-Ductile Transition at the Sierra Crest Shear Zone, Eastern Sierra Nevada, California”

Wilkins, Shaun (Langan – Professional)

“500-foot Slip or Slide”

Woodard, Brennen (CSUF – Undergraduate)

“The Requirements for Constructing a Favorable Recharge Well in San Juan Capistrano, California”

Abstract:

Cone Penetrometer Test (CPT) soundings are an often-used method to characterize subsurface soil behavior properties mostly in soft material conditions. The method has many geotechnical applications, some of which include liquefaction analysis, mapping of alluvial deposits and fill, evaluation of soil density improvement and determination of seismic S- and P-wave velocities. When a series of CPTs is advanced, the subsurface stratigraphy can be profiled. This was recognized early on and soon CPTs were engaged to identify stratigraphic disruptions indicative of faulting. This method is now widely used in the coastal province of Southern California, mostly in upper Quaternary materials. Oftentimes, only several feet or less of vertical differential across unit horizons or thickness variations in strata are used to identify potential faulting. This means it is imperative that depth recording of CPTs are as accurate as possible.

Several factors can cause errors in depth readings, leading to erroneous interpretations of faulting. These factors will be discussed in this presentation as well as a quality control procedure to track actual depths and thus mitigate errors. In addition, several examples will be presented where inaccurate depth readings resulted in misinterpretation of faulting. Finally, both the advantages and limitations of the CPT method will be discussed.

Abstract:

The advancement of fiber optic distributed sensing over the past two decades has enabled the measurement of subsurface hydraulics and geomechanics at unprecedented temporal and spatial detail. Fiber optic distributed sensing systems operate by firing laser light down a fiber optic cable and using backscattered photons to measure temperature, vibration, or strain. Kilometers of measurements can be made at scales as small as a centimeter and at sampling intervals of less than a millisecond.

We will look at how this technology has improved our understanding of subsurface flow related to diverse applications such as stream discharge, managed aquifer recharge, remediation of contaminated sites, aquifer testing, fracture hydromechanics, and energy resources. As these instruments become more reliable, accurate, and economical, opportunities for revolutionary observations of groundwater systems will continue to expand in the coming decades.

Abstract:

From late December 2022 until late March 2023, sixteen atmospheric river (AR) events impacted California, resulting in year-to-date precipitation accumulations varying from more than 200 to 350% above average across a wide swath of the state. Historic flooding and multi-modal landslide activity occurred statewide, damaging transportation infrastructure, homes, property, and threatening life-safety and economic welfare. A state of emergency was declared by the Governor of California as well as by the President of the United States. The California Governor’s Office of Emergency Services (CalOES) mission tasked the California Geological Survey (CGS) to provide situational awareness of statewide landslide hazards, which CGS accomplished in partnership with the United States Geological Survey (USGS) as well as numerous state, county, and local agencies.

CGS leveraged its Reported Landslides Database (RLD) mapping tools for desktop and field surveying to rapidly identify areas of observed landslide impacts, which included activation of a Landslides Triage Team (LTT). For several months the LTT gathered data from multiple sources including, but not limited to, photos and timing information from crowd-sourced reporting (e.g., Twitter, Facebook), local news media sources, state agency reporting, California Highway Patrol data, and review of firsthand reports.

The LTT identified more than 1000 AR-induced landslide events, necessitating the development of a GIS dashboard for efficient data organization. The GIS dashboard informed leadership of hardest hit areas and provided real-time support for community recovery accomplished by deployment of CalOES-requested CGS field teams at fourteen locations statewide. These mission tasks involved multi-partner agency collaboration and implementation of innovative field mapping, hazard surveying, and data collection methods. Here we highlight CGS mission task methods and results and discuss the successful public awareness campaign CGS developed to communicate the evolving nature of landslide hazards statewide. This public communication included an emergency response website, consistent Twitter communications to provide daily updates of a statewide landslide event density map, and a statewide deep-seated landslide “barometer” map.

Abstract:

Southern California is not new to unusual weather patterns and this past year did not disappoint. Between getting an abundance of rainfall in the winter season and a surprising tropical storm in August, how much rain did we receive and capture this past year? Are we ready for what’s ahead? Hear about what the Orange County Water District is doing to maximize stormwater capture and groundwater recharge opportunities which increase drinking water supplies for Orange County.