We are pleased to announce that SDAG has awarded the 2009 SDAG Scholarship to Jared Warner for his research project entitled "Biotic Response of Ostracodes to the Middle Eocene Climatic Optimum (MECO) in the Southern Indian Ocean".
Jared will receive a scholarship check and will present his research at an SDAG meeting this spring (usually the third week in March).
SAN DIEGO ASSOCIATION OF GEOLOGISTS
Potential Controls Affecting Gastropod Biomass in the the High Intertidal Zones at Neighboring Locations
Tiffany Schillereff
B.S. Candidate
Advisors Dr. Stephen Schellenberg
Friday, December 12th, 2008 CSL 422, 9:40am
ABSTRACT
San Diego California’s coastlines include rocky intertidal zones that contain an abundance of the Class Gastropoda. What are the potential controls on gastropod abundance and size? Do wave energy, anthropogenic impact, substrate lithology and predation play a role?
The locations in this study were Bathtub Rock and Dike Rock. Bathtub rock is located approximately 1 km south of the main parking lot at Torrey Pines State Beach. Dike Rock is located 1.1 km north of Scripps Institute of Oceanography pier and there is an approximate 3.3 km distance in between the two locations.
Bathtub rock is a medium grained sandstone sea stack that waves eroded from the Delmar Formation. Dike Rock is a basaltic andesite volcanic intrusion. Dike Rock is part of the Scripps Marine Coastal Reserve (no harvesting of specimens or shell collection allowed) and a submarine canyon (Scripps Canyon) is located off shore. Bathtub rock is not protected and no submarine canyon is located off shore.
Abundance counts, size measurements, and photographs (for identification) were collected in the upper middle to lower upper intertidal zones at laterally correlated MLLW’s at the two locations. These counts and measurements were also collected on the south side and north side at each location. These data were collected over a four month interval from September to December 2008.
The observed gastropods in the study include: Littorina planaxis, Collisella digitalis, Collisella scabra, Lottia gigantea and Nucella emarginata. N. emarginata was only observed at Dike Rock. All species of gastropods in this study prefer the upper middle to lower upper intertidal habitat. All but N. emarginata are algae grazers. N. emarginata is predatory and feeds on mussels, barnacles and other gastropods.
Overall gastropod abundances were higher at Bathtub rock with an average abundance of 537 ± 268 (1 σ) gastropods/m2 vs. an average abundance of 247 ± 56 (1 σ) gastropods/ m2 at Dike Rock. South side abundances were higher at both locations than the north side abundances. The south side of Bathtub Rock had an average of 727 ± 118 (1 σ) gastropods/m2 whereas the south side of Dike Rock had an average of 288 ± 47 (1 σ) gastropods/m2. The north side of Bathtub Rock had an average of 348 ± 58 (1 σ) gastropods/m2 whereas the north side of Dike Rock had an average of 207 ± 26 (1 σ) gastropods/m2. Overall gastropod size varied between the two locations with Dike Rock having an overall larger average size of 15 mm versus 7 mm at Bathtub Rock.
The higher abundance of gastropods at Bathtub rock could be due to the site’s more easily bioeroded sandstone (facilitating more dwelling structures) and fewer predatory N. emarginata gastropods and sea stars. The higher abundances on the southern side of both sites could reflect the average west-northwest incoming wave energy, which might preferentially dislodge gastropods from the northern sides. Larger average specimen size at Dike Rock could be due to the presence of the submarine canyon which refracts wave energy away from the site, providing full growth potential. Gastropods at wave-swept sites due to the probability of dislodgement by mechanical drag forces increases morality rates before they can achieve maximum size (Denny et al. 1985.) Another factor that could be affecting the larger size at Dike Rock is that it is a protected marine reserve. Anthropogenic impacts such as harvesting specimens have contributed to size declination over time (K. Roy et al. 2007.) Larger gastropod species Lottia gigantea and Nucella emarginata are present at this site which could be another factor.
Study of crustal structure in the Caucasus and Caspian regions using receiver functions
Rumi Takedatsu
B.S. Candidate
Advisors Dr. Rob Mellors
Friday, December 12th, 2008 CSL 422, 9:00am
ABSTRACT
The Eurasia-Arabia collision has created complex tectonics and structure in the Caucasus and Caspian region. In particular, Caspian Basin has a very different lithospheric structure from the surrounding region and the origin of the basin and nearby structures, such as the Kura Depression, are not well understood. This study will map the main crustal structure and estimate Moho depth under each seismic station using receiver functions. Receiver functions are a well-established technique to determine the boundary between crust and upper mantle (Moho) using three-component broadband seismograms. Using seismic data from 14 broadband stations in Azerbaijan, we generate receiver functions for 90 events. The Moho depth beneath each is determined by forward modeling the receiver functions using a reflectivity method and a two-layer crust. The receiver functions show clear indications of dipping structure as well as thick sediments under many stations which make modeling difficult. The preferred results show Moho depths of 37 - 43 km under the Greater Caucasus, 46 km under the Lesser Caucasus, 34 – 42 km in the Kura Depression, and 31 – 35 km along the western boundary of the South Caspian Basin. Crustal thickness thins towards the Caspian
Paleoenvironments, Paleoecology, and Exceptional Preservation in Burgess Shale-type Deposits
Robert Gaines
Department of Geology
Pomona College
Wednesday, December 10th, 2008
Cambrian Burgess Shale-type (BST) deposits occur worldwide and offer a remarkable window on the initial Phanerozoic radiation of the Metazoa. However, BST deposits also represent significant deviations from the constraints that govern the typical operation of the fossil record. These deviations remain to be adequately accounted for, hindering interpretations of the paleoecology of their exceptional biotas and the environments in which they lived. This talk will provide an overview of ongoing research towards developing a model for understanding paleoenvironments, paleoecology, and exceptional preservation in BST deposits, using data from 12 deposits of North America, Scandinavia and South China. Recently, elemental mapping of a survey of BST fossils demonstrated that the mode of fossilization is unique and common to all deposits. Thus, preservation of BST assemblages represents a single phenomenon that may share a common cause in all deposits in which it occurs. Sedimentologic and stratigraphic data indicate that BST deposits occur in a particular physical depositional window that acted as a first-order control, determining where exceptional fossilization occurred. Ichnologic and geochemical data indicate that, within the favorable physical depositional setting, benthic redox conditions exerted the next control. BST deposits occur at the transition from oxic to anoxic benthic environments and demonstrate dynamic redox conditions during deposition; exceptional fossils are confined to anoxic intervals. The chemistry of the early burial environment is interpreted to have exerted the final control. Ongoing work using the δ34S system from a core through the Chengjiang deposit extracted in July 2008 will provide a test of the hypothesis that sediment sealing by early carbonate cements promoted an early cessation of decay. Constraints at each tier, from the regional scale to the micron scale, were strongly favored by the prevalence of large epicratonic seaways in the Cambrian and by greenhouse conditions.
Characterizing an Artificial-Recharge Site in a Desert Environment Using Time-Domain Electromagnetics
Matt Burgess
M.S. Candidate
Advisors Dr. George Jiracek, Dr. Paul Bedrosian (USGS)
Friday, December 12th, 2008 CSL 422, 11:00am
ABSTRACT
Time-domain electromagnetics (TEM) were applied to characterize the
subsurface in the vicinity of a proposed artificial hydraulic recharge
site. Because of the investment involved, it is important to know the
possible barrier effect of a major fault situated near the proposed
recharge site. In this study, a series of TEM soundings were made to
estimate the depth to water on both the north and south sides of the
Pinto Mountain Fault. Results show strongly contrasting resistivity
structures across the fault. These findings are consistent with
expected water levels south of the Pinto Mountain Fault and suggest
that the fault does, in fact, act as a barrier to flow in the vicinity
of the proposed artificial recharge site.
Crustal Structure of the Caucasus/Caspian region using gravity and receiver functions
Jason Ricketts
B.S. Candidate
Advisor Dr. Rob Mellors
Friday, December 12th, 2008 CSL 422, 9:20am
ABSTRACT
The area west of the South Caspian basin is an area of complex and uncertain tectonic structure. Thick sediments within the Kura Depression mask the basement and its subsurface geology is poorly constrained. Forward modeling of receiver functions provides initial constrains. However, a good match is sometimes difficult due to the thick sediments. To further constrain the sedimentary thickness, a 2-D gravity profile from EGM2008 is forward modeled using 2 layers over a half-space.
The 2-D profile extends between the two seismic stations BRD and ALI, and the initial model was based on receiver function results. Gravity data was then used to verify these results as well as to provide any additional constrains on the model.
A proposed cross-section shows a depth to basement of 8 km beneath BRD, and a depth of 18 km beneath ALI. Gravity data also suggests that the sediment-basement contact between these two stations is highly irregular. A model where the basement displays an anticinal shape fits the gravity data as well as the receiver functions. Also located to the south of the profile is the Saatly deep well, which reaches a depth of more than 8 km without hitting basement. The westward component of motion of the South Caspian basin relative to the Kura Depression creates E-W shortening in this region, which can be supported by this model.
Southern Coyote Creek Fault to Superstition Hills Fault: New Insight to the San Jacinto Fault System
Afton Van Zandt
M.S. Candidate
Advisors Dr. Rob Mellors , Dr. Thomas K. Rockwell, and Dr. Douglas A. Stow
Friday, December 12th, 2008 CSL 422, 10:00am
ABSTRACT
The Superstition Hills fault (SHF) is an active fault in the San Jacinto fault zone that also creeps aseismically. 58 interferograms from ERS-1 and ERS-2 satellite data (descending, track 356, frame 2943) spanning a time period from 1992 to 2000 were analyzed to measure surface deformation along and near the fault. Interferograms were analyzed separately and as a stacked image. Clear signals due to both groundwater extraction and tectonic movement were observed. Fault creep is observed along the Superstition Hills and Elmore Ranch faults. A broad zone of line-of-sight deformation extends from the north end of the Superstition Hills fault to the southernmost Coyote Creek fault. Phase gradient images were useful in identifying faults, and revealed a previously unknown extension of the Coyote Creek fault.
The existence of the fault was confirmed by field measurements, which included both surface mapping and a trench across the fault. The fault exhibited indications of recent motion including both vertical and strike-slip components.
The InSAR data is modeled using a series of finite faults in an elastic half-space. The observed deformation along the Superstition Hills fault and Elmore Ranch fault can be modeled assuming shallow (< 5 km) creep. Various models were tested to explain the pattern of surface deformation between the Superstition Hills and Coyote Creek fault. The preferred model included a northwest trending vertical right-lateral strike-slip fault north of the Elmore Ranch fault.
LA's Future Earthquake
Kim Bak Olsen
Department of Geological Sciences
San Diego State University
Wednesday, December 3rd, 2008
'Hot' Professors
RateMyProfessors.com ranks two SDSU professors as most attractive.
SDSU'S Corey Manchester, lecturer in the Department of Mathematics and Statistics, and Isabelle SacramentoGrilo, lecturer for the Department of Geological Sciences, were ranked third and fourth respectively for hottest professors by RateMyProfessors.com, an online rating site for college, university and junior college professors.
The website recently ranked the top 10 rated universities, professors at universities, professors at junior colleges and hottest professors, using information gathered over the past two and a half years, with an emphasis on most recent ratings.
Each year RateMyProfessors.com's annual rankings capture the highest rated college professors and faculties on the site.
About the rankings
RateMyProfessors.com uses a five-point Likert scale, as well as a binary scoring system, for student-generated professor ratings.
For each of the professor lists, each individual rating value was first standardized around its mean and a weighted score was created using standardized scores from the years 2006, 2007 and 2008 to date.
Using the weighted score, professors were ranked from high to low. Only professors with 10 ratings or more were included to provide statistical significance. All professors were verified as actively teaching in the current semester by each school at the time the lists were compiled.
About the website
RateMyProfessor.com is a website where students can rank their professors on easiness, helpfulness, clarity, rater interest and "hotness."
In the past year, monthly traffic to the site has increased approximately 18 percent in page views, and about 20 percent in visits on average, according to Omniture. The lists were culled from RateMyProfessors.com's extensive database of more than 7.5 million student-generated ratings of over 1,000,000 college professors.
