Field Trips through southern Nevada and eastern California SUMMARY REPORT

Transcription

1 Field Trips through southern Nevada and eastern California SUMMARY REPORT Submitted to: Offshore Energy Research Association of Nova Scotia (OERA) to fulfill the requirements of the Student Research Travel Program Submitted by: Yuqiu Zhao Earth Sciences Dalhousie University June 25 th, 2017

2 TABLE OF CONTENTS Introduction... [2] Trip Details & Background Information... [2] Benefits of Travel... [5] Outcomes of Travel... [6] Significance to Nova Scotia... [6] Acknowledgements... [6] Reference... [7] 1

3 INTRODUCTION Dalhousie University Advanced Field School required a round travel from Halifax to Las Vegas and involved field trips through southern Nevada and eastern California from April 30 th to May 29 th. The 4-week long field course mainly focused on geological mapping and included 4 mapping projects related to sedimentology, stratigraphy, geomorphology, and structural and metamorphic geology. The field trips began at Frenchman Mountain, east of Las Vegas, in southern Nevada, and involved Death Valley and White Mountains in eastern California. During field trips, we camped at 3 different campground, Valley of Fire, Furnace Creek, and Westgard Pass (Figure 1). Under the leadership of Program Supervisor, Michael Young, we not only learned regional geology background and improved professional observational and analytic abilities, but also gained valuable fieldwork experience in groups and camping life experience. After each project, we completed stratigraphic column or geological map or both and short report, by group or by individual. The report summarizes all the field trips, benefits and outcomes of travel, as well as significance to Nova Scotia. TRIP DETAILS & BACKGROUND INFORMATION Field trips were organized around three campsites: Valley of Fire in southern Nevada and Furnace Creek, Death Valley and Westgard Pass, White Mountains in eastern California (Figure 1). The first project introduced Basin and Range tectonic environment in southern Nevada which formed after experiencing the Paleozoic deposits, the Mesozoic compression, and the Cenozoic extension, and the Grand Canyon stratigraphic sequence of Frenchman Mountain including the Proterozoic crystalline basement (~2.2Ga), the lower Cambrian clastic rocks, the Paleozoic carbonates, and the Mesozoic deposits (Figure 2; Young, 2017). This project involved 3-day field trips through Frenchman Mountain, Rainbow Gardens, Beaverdam Mountains, and Lake Mead, as well as 3-day long Rainbow Gardens exercise (Figure 1. [1]- [4]). In the first exercise, we studied sedimentology and stratigraphy of Horse Spring Formation and discussed its depositional environment and tectonic processes. The second project studied lithology and structural and metamorphic geology along Monarch Canyon where locates in the central part of the Sevier Orogeny deformation front and the Basin and Range extensional domain at northern Funeral Mountains in Death Valley area in eastern California. This project involved 2-day field trips through the opening of Death Valley, Canyon Turtleback, and Badwater Basin, and 3-day Monarch Canyon exercise (Figure 1. [5]- [8]). The shape of the domiform turtleback was formed due to the formation of metamorphic core complex controlled by normal shear on a ductile-brittle detachment. Monarch Canyon geology shows three structural levels: the oldest involves lower Crystal Springs Formation including pegmatite, pelites, psammite, amphibolite, and gneiss; the middle level mainly consists of pelitic schists and marbles of the Neoproterozoic Pahrump Group and Noonday Formation (Figure 3); the youngest includes undeformed dolostone and quartzite of the Cambrian Stirling Quartzite (Young, 2017). There are two detachment faults and the Cretaceous gt-st-ky (sill) mineral assemblage observed in study area. Through this exercise, we completed geological map, cross section, sense indicator sketches, stereonet, and interpretation of deformational, metamorphic, magmatic, and regional events. 2

4 [13] [14] [12] [15] [16] [3] [11] [9] [8] [10] [6] [7] [5] [1] [2] [4] Figure 1. Map of Southern Nevada and Eastern California, based on the map in Dalhousie University Advanced Field School Field Guide (Young, 2017). Stars show three campsites. [1] - Frenchman Mountain, [2] - Rainbow Gardens, [3] - Beaverdam Mountains, [4] - Lake Mead, [5] Dante s View, [6] - Canyon Turtleback, [7] - Badwater Basin, [8] Monarch Canyon, [9] Mesquite Flat Sand Dunes, [10] Darwin, [11] Whitney Portal, [12] Pumice Quarry, Northern Bishop, [13] Panum Crater & Tufa Towers at Mono Lake, Long Valley Caldera, [14] Owens Valley Gorge, [15] Big Pine Pendant, & [16] Poleta Folds. N S Paleozoic Carbonates Lower Cambrian Clastic Rocks Proterozoic Crystalline Basement m Figure 2. Eastern dipping Grand Canyon stratigraphic sequence of Frenchman Mountain showing the Proterozoic crystalline basement (~2.2Ga), the lower Cambrian clastic rocks, and the Paleozoic carbonates. Thick red dash line shows noncomformity while thin red dash line refers to approximate contact between the lower Cambrian clastic rocks and the Paleozoic carbonates. 3

5 SW NE Psammite Calc-silicates Marble Figure 3. Northeast dipping Monarch Canyon middle structural level involving light brown calc-silicates, white blue marble, and dark psammite. People can be considered as scale reference. Figure 4. Field site of Poleta Folds. Students were drawing structural cross section after lithologic, stratigraphic, and structural field observations. The last two projects were related to Big Pine Pendant and Poleta Folds around the third campground, Westgard Pass, White Mountains in eastern California. They involved 2-day field trips along the road from Death Valley to White Mountain and through Long Valley Caldera, 2-day Big Pine Pendant exercise, and 8-day Poleta Folds exercise (Figure 1. [9]- [16]). Long Valley Caldera is known as a giant bowl-shaped depression with approximately 32 km (east-west) 18 km (north- 4

6 south) in area, and it consists of rhyolite-dominated Bishop Tuff (Young, 2017). Through the Big Pine Pendant exercise, we studied skarn mineralization of the Paleozoic metasedimentary rocks and the Cretaceous granitic plutons, which is dominated by garnet and pyroxene, with mapping mineralogical contact zones. During Poleta Folds projects, we mainly studied deformed structures of Cambrian strata in the White Mountains, such as the Cenozoic high angle normal faults, thinskinned fold & thrust belt, and plutonism, in the rolling hills area of 3 km 4 km (Figure 4). This exercise also involved lithology, stratigraphy, and structural and metamorphic geology, and produced a measured stratigraphic section, a geologic map, and several cross sections. BENEFITS OF TRAVEL This travel program provides us with two main benefits. The first one is the systematic improvement of professional abilities like field observational and analytic abilities, mapping skills, group work skills, and integrated and practical ability of academic studies, and the obtainment of extensive fieldwork experience. For each project, we firstly learned geological history in the whole study area to help us to understand how regional tectonic or depositional environment system developed. Based on certain geologic context, we had field observations, records, measurements, and analyses under the help of supervisor or tutorial assistants. During the fieldwork, a series of field methods and skills were further enhanced and even mastered after repeated practices. After that, we discussed formation environments or history, depending on our data in groups and semiindependently or independently produced a short report with stratigraphic log or geologic map or both. The learning and practical process gives us a lifetime benefit in geology area. Figure 5. Campsite at Valley of Fire in southern Nevada. 5

7 The other benefit is that we gained the most valuable experience in camping life of wellfunctioning community (Figure 5). We built up a temporary kitchen and an office room. During camping life, we were divided into groups to do cooking and cleaning duties each day. We helped each other and cared for each other. We watched sunrise and sunset together, and talked around campfire every night. The most importantly, we worked together in field sites and shared knowledge and experience each other. We not only enhanced professional skills and camping skills but also improved communication skills and developed the ability to get along with people. Undoubtedly, this travel experience leaves everybody unforgettable memory with lots of fun. OUTCOMES OF TRAVEL The outcomes of travel are significant and satisfactory in three aspects. The direct outcomes we can see are geologic maps, stratigraphic columns, and structural cross sections. These results record our learning experience and reflect our improvements. The other two aspects are the enhancement of various abilities and skills and the establishment of friendship. After this program, we know how to combine academic studies with field practice and are further familiar with field skills and mapping skills. The most valuable is that we know each other more and more through living as a camping community and that we developed great friendship each other. Any of these outcomes is benefitable for us in the future. SIGNIFICANCE TO NOVA SCOTIA This program is also important to Nova Scotia due to two main reasons. Firstly, students can further understand geology in Nova Scotia by comparing with geology in southern Nevada and eastern California. During each project, combining with geological history in Nova Scotia, geologic events in southern Nevada and eastern California were introduced, especially similar lithologic units in the same period. This process is very helpful for students to further understand Nova Scotia geology and to improve their professional ability. Also, this learning and practice process during this program inspired students enthusiasm to further contribute to Nova Scotia in geology area. In personal view, attending this field school made me more confident and energetic than before. I would like to study more and go further in geology area, so I believe I can pay more for Nova Scotia. ACKNOWLEDGEMENTS I would like to express my hearty gratitude to the Offshore Energy Research Association of Nova Scotia (OERA) and all the sponsors and supporters of this program. Under your supports, many students like me can participate in this field school without high financial stress. I would like to express my sincere thanks to our program supervisor, Michael Young, and tutorial assistants, Carolina Chang, Nick Hosek, and Sean Kelly, for guiding me through the whole field trips with their rich fieldwork experience, encouragement, and patience. Their help has made me complete this program a valuable and fun learning experience. I would also like to thank all my partners and classmates for their understanding, patience, 6

8 encouragement, and help. I sincerely wish them to fly higher and go further in geology area. REFERENCE Young, M Dalhousie University ERTH 4002: Advanced Field School Geological Mapping, April 30 May 28, 2017, Southern Nevada and Eastern California. Dalhousie University, N.S. 7