Collaborative Research: RUI: Intergrated Isotopic Provenance Analysis: Constraining the Dynamic Linkage between Orogenic Exhumation and Basin Evolution

边缘盆地保存了大陆边缘造山系统空间和时间演化的详细记录。研究的重点是造山系统的折返历史如何保存在古代地层记录中，以及从派生的沉积序列中提取这一历史的保真度有多高这一根本问题。它集成了互补的同位素碎屑物源技术，以约束物源区的非均质性、折返模式和速率、沉积物扩散特征和盆地沉降机制。具体地说，这项研究正在测试多种同位素技术(碎屑锆石U-Pb年代学、全岩ND分析和碎屑钾长石和白云母40Ar/39Ar热年代学)与传统沉积学分析(生物地层学、岩石地层学和岩石学研究)相结合的有效性，以评估造山作用、盆地沉降和由此导致的大陆边缘弧系沉积物扩散和聚集之间的动态联系。这项研究的一个关键方面是开发和应用与碎屑矿物40Ar/39Ar闭合年龄分布相关的新的分析和模拟方法。对加州北部半岛山脉沉积物中钾长石的40Ar/39Ar全熔融分析的初步结果表明，该方法可以提供灵敏、高分辨率的深部基底折返记录。要将该方法有意义地应用于石器时代前的源区，需要对侵入体历史进行表征，需要碎屑U-Pb锆石年代学来提供基底结晶年龄。利用细粒碎屑岩全岩Nd3+同位素分析，约束了沉积物扩散和堆积模式的源区非均质性和时空变化。正在研究的两个盆地在年龄、物源和沉积环境方面具有广泛的一级相似性，但在各自的石器时代源区具有强烈的同沉积地壳折返记录。下加利福尼亚州的Vizcaino盆地暴露在相对较浅(5-10公里)的半岛山脉基岩附近，在那里，大体积基岩侵位似乎触发了一段明显的加速弧剥蚀事件。不列颠哥伦比亚省南部的纳奈莫盆地暴露在海岸深成杂岩的深度侵蚀(20-30公里)岩浆弧岩旁边，这些岩浆弧岩是在更复杂的深成岩浆作用和区域变形的相互作用下被挖掘出来的。这两个盆地都具有年代较长的地层连贯序列，跨越了各自源区地区的折返事件。这为解释派生沉积记录中记录的基底折返历史的细节提供了必要的解释框架。本科生研究合作者深入参与了本次调查期间进行的野外和实验室分析的所有方面。学生合作者(n~12人)参与了威斯康星大学和圣地亚哥州立大学的地层分析、沉积岩石学、地球化学和同位素分析。

Marginal basins preserve a detailed record of the spatial and temporal evolution of orogenic systems along continental margins. This investigation focuses on the fundamental question of how the exhumation history of orogenic systems is preserved in the ancient stratigraphic record, and with what fidelity this history can be extracted from derivative sedimentary successions. It integrates complementary isotopic detrital provenance techniques to constrain source area heterogeneity, exhumation patterns and rates, sediment dispersal characteristics, and basin subsidence mechanisms. Specifically, the study is testing the utility of integrating multiple isotopic techniques (detrital zircon U-Pb geochronology, whole rock Nd analyses, and detrital K-feldspar & muscovite 40Ar/39Ar thermochronology) with traditional sedimentologic analyses (biostratigraphic, lithostratigraphic and petrologic studies) to assess the dynamic linkage between orogenesis, basin subsidence and resultant sediment dispersal and accumulation in continental margin arc systems. A key aspect of this investigation is development and application of new analytical and modeling approaches associated with 40Ar/39Ar closure age distributions of detrital minerals. Preliminary results utilizing total fusion 40Ar/39Ar analysis of K-feldspar from sediments derived from the northern Peninsular Ranges of California indicate that indicate this method can provide a sensitive, high-resolution record of deep basement exhumation. Meaningful application of the method to batholithic source regions requires characterization of intrusion history, necessitating detrital U-Pb zircon geochronology to provide basement crystallization ages. Source area heterogeneity and temporal and spatial variations in sediment dispersal and accumulation patterns are constrained using whole rock neodymium isotopic analyses of fine-grained clastic rocks. Two basins that share broad first-order similarities in age, provenance and depositional setting, but have strongly constrasting syn-sedimentary crustal exhumation records in their respective batholithic source regions are being examined The Vizcaino basin of Baja California is exposed adjacent to the relatively shallowly exhumed (5-10 km) Peninsular Ranges batholith where a distinct episode of accelerated arc denudation appears to have been triggered by large-volume batholith emplacement. The Nanaimo basin of southern British Columbia is exposed adjacent to deeply eroded (20-30 km) magmatic arc rocks of the Coast Plutonic Complex that were exhumed in response to a more complex interplay of plutonism and regional deformation. Both basins have well-dated stratigraphically coherent successions that span the exhumation events in their respective source regions areas. This provides the necessary interpretive framework to interpret details of basement exhumation histories recorded in the derivative sedimentary record.Undergraduate student research collaborators are heavily involved in all aspects of field and laboratory analyses conducted during this investigation. Student collaborators (n~12) are participating in stratigraphic analysis, sedimentary petrology, geochemistry, and isotopic analysis at both the University of Wisconsin-Eau Claire and San Diego State University.