SGER: Triassic-Jurassic Mass Extinction Caused By Volcanism? Carbon Isotopic Tests In Eastern North America And Morocco

Sger：三叠纪-侏罗纪大灭绝是由火山活动引起的？北美东部和摩洛哥的碳同位素测试2亿年前的三叠纪-侏罗纪（Tr-J）边界标志着地球上最严重的物种大灭绝之一，其规模可与著名的白垩纪-第三纪（K-T）边界相媲美。虽然它显然摧毁了当时存在的至少一半的陆地多样性，但它为恐龙主导的生态系统的崛起奠定了生态基础。与K-T和二叠纪-三叠纪大灭绝一样，Tr-J大灭绝与地球上最大的洪水玄武岩事件——中大西洋岩浆省（CAMP）——有暂时的联系。先前对北美东部纽瓦克和芬迪裂谷盆地的Tr-J边界的研究，以及其他人对海洋和大陆沉积物的研究表明，与K-T边界有更多的相似之处，包括适度的Ir异常、“蕨类植物尖”、气孔（CO2）异常和一对负13C偏移。虽然这些观测结果与外星撞击有关，但这些证据中的大部分（如果不是全部的话）也与CAMP的巨大洪水玄武岩一致。然而，来自北美东部的数据表明，所有CAMP的流动都晚于灭绝水平数万年，这使得因果关系不太可能。然而，有一些迹象表明，摩洛哥的一些CAMP熔岩确实早于Tr-J边界或与之同步，这可能是CAMP灭绝的原因。PI将采用双管齐下的方法来测试这种可能性。首先，她与摩洛哥的同事和一名研究生合作，建议建立直接包围和互层的Mo-roccan CAMP玄武岩地层的有机13C化学地层学（包括来自叶角质层蜡的块状和特定化合物正构烷烃）。其次，为了更好地描述纽瓦克盆地有机13C的边界前变化，她将在杰克逊瓦尔德向斜边界以下125米（~400千米）的岩芯中恢复有机13C地层，这是P.E. Olsen和D.V. Kent领导的SGER项目的一部分。这两种方法将对是否已知的玄武岩喷发可能导致Tr-J大规模灭绝进行确定的测试。该项目还将使人们更好地了解伴随大规模灭绝而来的生态破坏的碳同位素特征，这反过来将对人类引起的变化和其他大规模火山爆发的长期影响和可能的意外或高度非线性后果提供更深入的见解。该奖项由地球科学部和国际科学与工程办公室共同资助。

SGER: TRIASSIC-JURASSIC MASS EXTINCTION CAUSED BY VOLCANISM? CARBON ISOTOPIC TESTS IN EASTERN NORTH AMERICA AND MOROCCOJessica WhitesideEAR-0801138, Brown UniversityABSTRACTThe Triassic-Jurassic (Tr-J) boundary, 200 million years ago, marks one of the Earth's most severe mass extinctions, comparable in magnitude to that of the famous Cretaceous-Tertiary (K-T) boundary. While apparently decimating at least half of then-extant terrestrial diversity, it set the ecological stage for the ascent of dinosaur-dominated ecosystems. As with the K-T and Permo-Triassic mass extinctions, the Tr-J mass extinction is temporally linked to the Earth's largest flood basalt event, the Central Atlantic Magmatic Province (CAMP). Previous work on the Tr-J boundary in the Newark and Fundy rift basins of eastern North America and work by others in marine and continental deposits demonstrate additional parallels to the K-T boundary including a modest Ir anomaly, a "fern spike," a stomatal (CO2) anomaly, and a pair of negative 13C excursions. While these observations as condign with an extraterrestrial impact, much if not all of this evidence is also consonant with the giant flood basalts of the CAMP. However, data from eastern North America suggest that all CAMP flows post-date the extinction level by tens of thousands of years, making causation unlikely. However, there is some suggestion that some Moroccan CAMP lavas do predate or were synchronous with the Tr-J boundary, making it pos-sible that the CAMP was the cause of the extinctions. PI will use a two-pronged approach to test this possibility. First, working with Moroccan colleagues and a graduatate student, she proposes to establish the organic 13C chemostratigraphy (including bulk and compound-specific n-alkanes from leaf cuticular waxes) of strata directly surrounding and interbedded with the Mo-roccan CAMP basalts. Second, to better characterize the pre-boundary variations in organic 13C in the Newark basin, thus far poorly known, she will recover the organic 13C stratigraphy in a core penetrating 125 m (~400 ky) below the boundary in the Jacksonwald Syncline to be recov-ered as part of a SGER project led by P.E. Olsen and D.V. Kent. These two approaches will al-low a definitive test of whether any known basalt eruptions could have cause the Tr-J mass ex-tinction. The project will also result in an much better understanding of the carbon iso-topic signatures of ecological disruption accompanying a mass-extinction, which in turn, will provide deeper insight into the long-term implications and possible unex-pected or highly non-linear consequences of human-induced changes and other mas-sive volcanic eruptions.This award is co-funded by the Division of Earth Sciences and Office of International Science and Engineering.