Geology/Earth Science Projects 2010

Sediment Core Analysis: Applications in Petroleum Geology and Groundwater Resources

Faculty Mentors - Drs. Robert Horton, Dirk Baron

Background Thick sequences of sediments in the San Joaquin Valley of California are host to the region's major oil and groundwater resources. This project will provide an introduction to the techniques that geologists use to characterize sediments and their potential as petroleum and groundwater reservoirs. Participants will then work on two applied research projects, one in petroleum geology and one in groundwater geology, with sediment samples from the San Joaquin Valley. Both projects will use the CSUB Geology Department's state-of-the-art research labs including the new scanning electron microscopy lab and the trace-element geochemistry lab. Participants will also visit Chevron's Kern River Oil Field and the groundwater extraction sites from which the samples for the studies were collected.

Petroleum Geology Kern County is the leading oil producing area in California; in fact, if Kern County was a state we would rank fourth in oil production among the United States! Most of Kern's oil fields have been in production for a long time and the easy oil was drained long ago. Much of what remains is so-called heavy oil that is too thick to simply flow from wells. In order to produce this oil, local producers inject steam into the reservoir to heat the oil and thus allow it to flow more freely. The injected steam also reacts with the reservoir rocks, and oil companies are interested in how these changes might affect future production as they try to manage this valuable resource in the most efficient manner.

In this project participants will be involved in cutting-edge research of significance to the local petroleum community. We will be studying core samples from local oil fields (including Chevron's Kern River Field) to determine the nature and distribution of the pore spaces in which oil resides and through which it must flow in order to be produced. We will look at and compare samples from cores obtained before and after the injection of steam to learn how heating has affected the composition of the sediments and the nature of the pore network. We will first examine whole core samples using our naked eyes and hand-held magnifying lenses, then we will select samples and process them for microscopic examination using CSUB's Scanning Electron Microscope (all participants will be trained to operate this remarkable instrument capable of greater than 10,000 times magnification).

Biotite (a type of mica) grain containing crystals of ankerite (Ca-Mg-Fe carbonate) that formed when the biotite reacted with hot water. The ankerite formed within the biotite grain and pushed the layers apart.

Heulandite crystals that formed in pore spaces in sand that had been injected with steam.

Groundwater Resources Groundwater is a hidden resource that is essential for Kern County and the San Joaquin Valley. Even in a year with average rain, about half of all water used in the region is groundwater, much more in dry years like the current and previous years. While most of our groundwater is of excellent quality, some parts of the valley have elevated concentrations of the toxic element arsenic.

n this project, we will examine sediments collected during the drilling of water wells in order to determine the reasons for elevated arsenic concentrations in groundwater. Previous work indicates that dissolution of small grains of the mineral pyrite ("fools gold") that contain traces of arsenic may be a contributing factor. So one thing we will be investigating is the abundance of pyrite and its arsenic content in the sediment samples.

Close-up view of pyrite crystals in shale showing dissolution textures. Well 23H, depth = 550 ft

The San Joaquin Valley over the Past 15,000 years: A Great Lake (and a Meteorite Impact?)

Faculty Mentors - Robert Negrini

After flowing through Bakersfield, the Kern River joins three other major streams, the Tule, the Kaweah, and the Kings Rivers, in feeding Tulare Lake (Figure 1). By mapping its ancient shorelines and analyzing its bottom sediments, CSUB faculty and students have reconstructed a lake-level history for this body of water, which represents the environmental and water resource history of the San Joaquin Valley for the past 10,000 years (Figure 2). This has implications in the establishment of environmental baselines, in constraining reconstructions of Native American habitats, and in planning for future water resource management in response to expected changes in climate.

This summer a series of analyses will continue on the shorelines and sediments of Tulare Lake designed to address all or some of the following problems:

1. Testing the Lake-Level Model. Does the presently proposed lake-level history (Negrini et al. 2006) stand up to further scrutiny? Science progresses as hypotheses are tested when their predictions are compared with related observations made after the fact. We'll make predictions of measurable quantities such as lake productivity, current velocity, etc. and then test the lake-level history by measuring total organic carbon, sediment grain-size, etc.
2. Looking for Evidence of a Catastrophic Meteorite. A recent controversial paper by Firestone et al. (2007) suggests that a meteor or comet impact 13,000 years ago was responsible for the rapid extinction of Pleistocene megafauna (e.g., Mammoths) and the Clovis people, and for a global cooling that lurched the Earth back into an ice age for ~1,000 years. We'll predict the location of this event in sediment cores from Tulare Lake based on radiocarbon dates and then inspect this interval for features associated with extraterrestrial impacts (e.g., nanodiamonds).
3. The Little Ice Age in the San Joaquin Valley. The youngest sediments associated with the highest shoreline of Tulare Lake were deposited over the past several centuries (from ~12th to the 17th centuries A.D.). Was this high lake a signature of the "Little Ice Age", an event that was likely hemispheric and maybe even global in scale? If so, does it contain characteristic oscillations that are timed consistently with records from elsewhere in the world? We'll predict the timing of these finer scale oscillations within the Little Ice Age and inspect sediments cores and trenches through these sediments for associated observations like grain-size change. We'll also place our results in the context of climate models (i.e., how pulses of high lake-level are or are not consistent with pulses of cold temperatures over this time period).

1. Negrini, R.M. et al., 2006. The Rambla Highstand Shoreline and the Holocene lake level history of Tulare Lake, California. Quat. Sci. Rev., v. 25, p. 1599-1618.
2. Firestone, R.B. et al., 2007. Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling, Proceedings of the National Academiy of Sciences, v. 104, p. 16016-16021.

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