Min Liu, Yen Joe Tan, Xinglin Lei, Hongyi Li, Yunpeng Zhang, Weitao Wang
Volcanic regions commonly host swarms comprising small to moderate-sized earthquakes while tectonic faults host mostly mainshock-aftershock sequences that can include very large earthquakes. In the southeastern Tibetan Plateau, large tectonic faults formed by the collision between the Indian and Eurasian plates intersect with the intraplate Tengchong volcanic field, and the seismic behavior of such an environment remains unclear. Here, we built a deep-learning-based high-precision earthquake catalog for the Tengchong volcanic field and found that (1) ∼59% of the seismicity occurred as swarms but on faults aligned with the regional tectonic stress field; (2) all swarms contained fluid-diffusion-like migration fronts, with some occurring where high CO2 emissions have been detected; and (3) a year-long swarm, including two ML 5.2 earthquakes within two months, revealed complex fluid-fault interaction. Combined with the historical occurrences of M >6 earthquake swarms around the Tengchong volcanic field, our observations suggest potential increased likelihood of swarms with large-magnitude earthquakes where large tectonic faults and magmatic systems intersect.
火山地区通常会发生由中小规模地震组成的地震群，而构造断层则大多会发生包括特大地震在内的主震-余震序列。在青藏高原东南部，印度板块和欧亚板块碰撞形成的大型构造断层与板块内的腾冲火山场相交，这种环境下的地震行为尚不清楚。在此，我们建立了基于深度学习的腾冲火山活动场高精度地震目录，并发现：（1）59%的地震活动以震群形式发生，但发生在与区域构造应力场一致的断层上；（2）所有震群都包含流体扩散样迁移前沿，其中一些发生在已探测到高二氧化碳排放的地方；（3）一个长达一年的震群，包括两个月内的两次 ML 5.2 地震，揭示了复杂的流体-断层相互作用。结合历史上腾冲火山区周围发生的 M > 6 级地震群，我们的观测结果表明，在大型构造断层和岩浆系统交汇的地方，发生大震级地震群的可能性可能会增加。
{"title":"Intersection between tectonic faults and magmatic systems promotes swarms with large-magnitude earthquakes around the Tengchong volcanic field, southeastern Tibetan Plateau","authors":"Min Liu, Yen Joe Tan, Xinglin Lei, Hongyi Li, Yunpeng Zhang, Weitao Wang","doi":"10.1130/g51796.1","DOIUrl":"https://doi.org/10.1130/g51796.1","url":null,"abstract":"Volcanic regions commonly host swarms comprising small to moderate-sized earthquakes while tectonic faults host mostly mainshock-aftershock sequences that can include very large earthquakes. In the southeastern Tibetan Plateau, large tectonic faults formed by the collision between the Indian and Eurasian plates intersect with the intraplate Tengchong volcanic field, and the seismic behavior of such an environment remains unclear. Here, we built a deep-learning-based high-precision earthquake catalog for the Tengchong volcanic field and found that (1) ∼59% of the seismicity occurred as swarms but on faults aligned with the regional tectonic stress field; (2) all swarms contained fluid-diffusion-like migration fronts, with some occurring where high CO2 emissions have been detected; and (3) a year-long swarm, including two ML 5.2 earthquakes within two months, revealed complex fluid-fault interaction. Combined with the historical occurrences of M >6 earthquake swarms around the Tengchong volcanic field, our observations suggest potential increased likelihood of swarms with large-magnitude earthquakes where large tectonic faults and magmatic systems intersect.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139800576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Jicha, A. Schaen, Bryan Wathen, William O. Nachlas
Clinopyroxene is a rock-forming mineral that commonly hosts melt inclusions in mafic to intermediate composition volcanic and plutonic rocks. It is highly resistant to alteration compared to other co-existing phenocrysts such as plagioclase. Several recent studies have 40Ar/39Ar dated clinopyroxene in Neoproterozoic to Miocene basalts and dolerites. To assess the viability of the technique at the youngest end of the geologic time scale, we performed 40Ar/39Ar incremental heating experiments on clinopyroxene-hosted melt inclusions from a variety of mafic lithologies and tectonic settings. Most samples produced precise plateau ages including several Quaternary basalts to andesites as young as 0.6 Ma. All data are indistinguishable from new and/or published 40Ar/39Ar ages on groundmass or plagioclase from the same samples. The source of potassium (K) and resulting 40Ar* within clinopyroxene has been debated, but thus far has only been inferred based on 40Ar/39Ar data. Using electron probe microanalysis (EPMA) we show that there is negligible K in the clinopyroxene host, but substantial K (e.g., 1–4 wt%) in trapped melt inclusions and minor amounts in plagioclase inclusions. Thus, melt inclusions, which are common in phenocrysts in basaltic magmas, can be used to obtain accurate and precise 40Ar/39Ar ages for difficult-to-date volcanic and plutonic rocks from the Precambrian to the Pleistocene.
{"title":"Precambrian to Pleistocene 40Ar/39Ar dating of clinopyroxene-hosted melt inclusions","authors":"B. Jicha, A. Schaen, Bryan Wathen, William O. Nachlas","doi":"10.1130/g51777.1","DOIUrl":"https://doi.org/10.1130/g51777.1","url":null,"abstract":"Clinopyroxene is a rock-forming mineral that commonly hosts melt inclusions in mafic to intermediate composition volcanic and plutonic rocks. It is highly resistant to alteration compared to other co-existing phenocrysts such as plagioclase. Several recent studies have 40Ar/39Ar dated clinopyroxene in Neoproterozoic to Miocene basalts and dolerites. To assess the viability of the technique at the youngest end of the geologic time scale, we performed 40Ar/39Ar incremental heating experiments on clinopyroxene-hosted melt inclusions from a variety of mafic lithologies and tectonic settings. Most samples produced precise plateau ages including several Quaternary basalts to andesites as young as 0.6 Ma. All data are indistinguishable from new and/or published 40Ar/39Ar ages on groundmass or plagioclase from the same samples. The source of potassium (K) and resulting 40Ar* within clinopyroxene has been debated, but thus far has only been inferred based on 40Ar/39Ar data. Using electron probe microanalysis (EPMA) we show that there is negligible K in the clinopyroxene host, but substantial K (e.g., 1–4 wt%) in trapped melt inclusions and minor amounts in plagioclase inclusions. Thus, melt inclusions, which are common in phenocrysts in basaltic magmas, can be used to obtain accurate and precise 40Ar/39Ar ages for difficult-to-date volcanic and plutonic rocks from the Precambrian to the Pleistocene.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139860297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Jicha, A. Schaen, Bryan Wathen, William O. Nachlas
Clinopyroxene is a rock-forming mineral that commonly hosts melt inclusions in mafic to intermediate composition volcanic and plutonic rocks. It is highly resistant to alteration compared to other co-existing phenocrysts such as plagioclase. Several recent studies have 40Ar/39Ar dated clinopyroxene in Neoproterozoic to Miocene basalts and dolerites. To assess the viability of the technique at the youngest end of the geologic time scale, we performed 40Ar/39Ar incremental heating experiments on clinopyroxene-hosted melt inclusions from a variety of mafic lithologies and tectonic settings. Most samples produced precise plateau ages including several Quaternary basalts to andesites as young as 0.6 Ma. All data are indistinguishable from new and/or published 40Ar/39Ar ages on groundmass or plagioclase from the same samples. The source of potassium (K) and resulting 40Ar* within clinopyroxene has been debated, but thus far has only been inferred based on 40Ar/39Ar data. Using electron probe microanalysis (EPMA) we show that there is negligible K in the clinopyroxene host, but substantial K (e.g., 1–4 wt%) in trapped melt inclusions and minor amounts in plagioclase inclusions. Thus, melt inclusions, which are common in phenocrysts in basaltic magmas, can be used to obtain accurate and precise 40Ar/39Ar ages for difficult-to-date volcanic and plutonic rocks from the Precambrian to the Pleistocene.
{"title":"Precambrian to Pleistocene 40Ar/39Ar dating of clinopyroxene-hosted melt inclusions","authors":"B. Jicha, A. Schaen, Bryan Wathen, William O. Nachlas","doi":"10.1130/g51777.1","DOIUrl":"https://doi.org/10.1130/g51777.1","url":null,"abstract":"Clinopyroxene is a rock-forming mineral that commonly hosts melt inclusions in mafic to intermediate composition volcanic and plutonic rocks. It is highly resistant to alteration compared to other co-existing phenocrysts such as plagioclase. Several recent studies have 40Ar/39Ar dated clinopyroxene in Neoproterozoic to Miocene basalts and dolerites. To assess the viability of the technique at the youngest end of the geologic time scale, we performed 40Ar/39Ar incremental heating experiments on clinopyroxene-hosted melt inclusions from a variety of mafic lithologies and tectonic settings. Most samples produced precise plateau ages including several Quaternary basalts to andesites as young as 0.6 Ma. All data are indistinguishable from new and/or published 40Ar/39Ar ages on groundmass or plagioclase from the same samples. The source of potassium (K) and resulting 40Ar* within clinopyroxene has been debated, but thus far has only been inferred based on 40Ar/39Ar data. Using electron probe microanalysis (EPMA) we show that there is negligible K in the clinopyroxene host, but substantial K (e.g., 1–4 wt%) in trapped melt inclusions and minor amounts in plagioclase inclusions. Thus, melt inclusions, which are common in phenocrysts in basaltic magmas, can be used to obtain accurate and precise 40Ar/39Ar ages for difficult-to-date volcanic and plutonic rocks from the Precambrian to the Pleistocene.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139800308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Min Liu, Yen Joe Tan, Xinglin Lei, Hongyi Li, Yunpeng Zhang, Weitao Wang
Volcanic regions commonly host swarms comprising small to moderate-sized earthquakes while tectonic faults host mostly mainshock-aftershock sequences that can include very large earthquakes. In the southeastern Tibetan Plateau, large tectonic faults formed by the collision between the Indian and Eurasian plates intersect with the intraplate Tengchong volcanic field, and the seismic behavior of such an environment remains unclear. Here, we built a deep-learning-based high-precision earthquake catalog for the Tengchong volcanic field and found that (1) ∼59% of the seismicity occurred as swarms but on faults aligned with the regional tectonic stress field; (2) all swarms contained fluid-diffusion-like migration fronts, with some occurring where high CO2 emissions have been detected; and (3) a year-long swarm, including two ML 5.2 earthquakes within two months, revealed complex fluid-fault interaction. Combined with the historical occurrences of M >6 earthquake swarms around the Tengchong volcanic field, our observations suggest potential increased likelihood of swarms with large-magnitude earthquakes where large tectonic faults and magmatic systems intersect.
火山地区通常会发生由中小规模地震组成的地震群，而构造断层则大多会发生包括特大地震在内的主震-余震序列。在青藏高原东南部，印度板块和欧亚板块碰撞形成的大型构造断层与板块内的腾冲火山场相交，这种环境下的地震行为尚不清楚。在此，我们建立了基于深度学习的腾冲火山活动场高精度地震目录，并发现：（1）59%的地震活动以震群形式发生，但发生在与区域构造应力场一致的断层上；（2）所有震群都包含流体扩散样迁移前沿，其中一些发生在已探测到高二氧化碳排放的地方；（3）一个长达一年的震群，包括两个月内的两次 ML 5.2 地震，揭示了复杂的流体-断层相互作用。结合历史上腾冲火山区周围发生的 M > 6 级地震群，我们的观测结果表明，在大型构造断层和岩浆系统交汇的地方，发生大震级地震群的可能性可能会增加。
{"title":"Intersection between tectonic faults and magmatic systems promotes swarms with large-magnitude earthquakes around the Tengchong volcanic field, southeastern Tibetan Plateau","authors":"Min Liu, Yen Joe Tan, Xinglin Lei, Hongyi Li, Yunpeng Zhang, Weitao Wang","doi":"10.1130/g51796.1","DOIUrl":"https://doi.org/10.1130/g51796.1","url":null,"abstract":"Volcanic regions commonly host swarms comprising small to moderate-sized earthquakes while tectonic faults host mostly mainshock-aftershock sequences that can include very large earthquakes. In the southeastern Tibetan Plateau, large tectonic faults formed by the collision between the Indian and Eurasian plates intersect with the intraplate Tengchong volcanic field, and the seismic behavior of such an environment remains unclear. Here, we built a deep-learning-based high-precision earthquake catalog for the Tengchong volcanic field and found that (1) ∼59% of the seismicity occurred as swarms but on faults aligned with the regional tectonic stress field; (2) all swarms contained fluid-diffusion-like migration fronts, with some occurring where high CO2 emissions have been detected; and (3) a year-long swarm, including two ML 5.2 earthquakes within two months, revealed complex fluid-fault interaction. Combined with the historical occurrences of M >6 earthquake swarms around the Tengchong volcanic field, our observations suggest potential increased likelihood of swarms with large-magnitude earthquakes where large tectonic faults and magmatic systems intersect.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139860551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiaodong Jiang, Xiangyu Zhao, Xiaoming Sun, Andrew P. Roberts, A. Sluijs, Yu‐Min Chou, Weiqi Yao, Jieqi Xing, Weijie Zhang, Qingsong Liu
The Paleocene–Eocene thermal maximum (PETM), a transient period of global warming, is considered to be an important analog for future greenhouse conditions. It was accompanied by a significant carbon cycle perturbation. Although ocean deoxygenation across the PETM is reported widely, its mechanism in the open ocean remains uncertain. Here, we present magnetic and geochemical analyses of sediments from the eastern equatorial Pacific Ocean. We found that iron fertilization during the PETM by eolian dust and volcanic eruptions fueled eastern equatorial Pacific Ocean productivity. This process led to increased organic matter degradation and oxygen consumption in intermediate waters, leading to deoxygenation. Our findings suggest that iron fertilization could be an important driver of open-ocean oxygen loss, as a side effect of global warming.
{"title":"Iron fertilization–induced deoxygenation of eastern equatorial Pacific Ocean intermediate waters during the Paleocene–Eocene thermal maximum","authors":"Xiaodong Jiang, Xiangyu Zhao, Xiaoming Sun, Andrew P. Roberts, A. Sluijs, Yu‐Min Chou, Weiqi Yao, Jieqi Xing, Weijie Zhang, Qingsong Liu","doi":"10.1130/g51770.1","DOIUrl":"https://doi.org/10.1130/g51770.1","url":null,"abstract":"The Paleocene–Eocene thermal maximum (PETM), a transient period of global warming, is considered to be an important analog for future greenhouse conditions. It was accompanied by a significant carbon cycle perturbation. Although ocean deoxygenation across the PETM is reported widely, its mechanism in the open ocean remains uncertain. Here, we present magnetic and geochemical analyses of sediments from the eastern equatorial Pacific Ocean. We found that iron fertilization during the PETM by eolian dust and volcanic eruptions fueled eastern equatorial Pacific Ocean productivity. This process led to increased organic matter degradation and oxygen consumption in intermediate waters, leading to deoxygenation. Our findings suggest that iron fertilization could be an important driver of open-ocean oxygen loss, as a side effect of global warming.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139803901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiaodong Jiang, Xiangyu Zhao, Xiaoming Sun, Andrew P. Roberts, A. Sluijs, Yu‐Min Chou, Weiqi Yao, Jieqi Xing, Weijie Zhang, Qingsong Liu
The Paleocene–Eocene thermal maximum (PETM), a transient period of global warming, is considered to be an important analog for future greenhouse conditions. It was accompanied by a significant carbon cycle perturbation. Although ocean deoxygenation across the PETM is reported widely, its mechanism in the open ocean remains uncertain. Here, we present magnetic and geochemical analyses of sediments from the eastern equatorial Pacific Ocean. We found that iron fertilization during the PETM by eolian dust and volcanic eruptions fueled eastern equatorial Pacific Ocean productivity. This process led to increased organic matter degradation and oxygen consumption in intermediate waters, leading to deoxygenation. Our findings suggest that iron fertilization could be an important driver of open-ocean oxygen loss, as a side effect of global warming.
{"title":"Iron fertilization–induced deoxygenation of eastern equatorial Pacific Ocean intermediate waters during the Paleocene–Eocene thermal maximum","authors":"Xiaodong Jiang, Xiangyu Zhao, Xiaoming Sun, Andrew P. Roberts, A. Sluijs, Yu‐Min Chou, Weiqi Yao, Jieqi Xing, Weijie Zhang, Qingsong Liu","doi":"10.1130/g51770.1","DOIUrl":"https://doi.org/10.1130/g51770.1","url":null,"abstract":"The Paleocene–Eocene thermal maximum (PETM), a transient period of global warming, is considered to be an important analog for future greenhouse conditions. It was accompanied by a significant carbon cycle perturbation. Although ocean deoxygenation across the PETM is reported widely, its mechanism in the open ocean remains uncertain. Here, we present magnetic and geochemical analyses of sediments from the eastern equatorial Pacific Ocean. We found that iron fertilization during the PETM by eolian dust and volcanic eruptions fueled eastern equatorial Pacific Ocean productivity. This process led to increased organic matter degradation and oxygen consumption in intermediate waters, leading to deoxygenation. Our findings suggest that iron fertilization could be an important driver of open-ocean oxygen loss, as a side effect of global warming.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139863779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Paleocene–Eocene thermal maximum (PETM; ca. 56 Ma) geological interval records a marked decline in calcium carbonate (CaCO3) in seafloor sediments, potentially reflecting an episode of deep- and possibly shallow-water ocean acidification. However, because CaCO3 is susceptible to postburial dissolution, the extent to which this process has influenced the PETM geological record remains uncertain. Here, we tested for evidence of postburial dissolution by searching for imprint fossils of nannoplankton preserved on organic matter. We studied a PETM succession from the South Dover Bridge (SDB) core, Maryland, eastern United States, and compared our imprint record with previously published data from traditionally sampled CaCO3-preserved nannoplankton body fossils. Abundant imprints through intervals devoid of CaCO3 would signify that postburial dissolution removed much of the CaCO3 from the rock record. Imprints were recorded from most samples but were rare and of low diversity. Body fossils were substantially more numerous and diverse, capturing a more complete record of the living nannoplankton communities through the PETM. The SDB succession records a dissolution zone/low-carbonate interval at the onset of the PETM, through which nannoplankton body fossils are rare. No nannoplankton imprints were found from this interval, suggesting that the rarity of body fossils is unlikely to have been the result of postburial dissolution. Instead, our findings suggest that declines in CaCO3 through the PETM at the SDB location were the result of: (1) biotic responses to changes that were happening during this event, and/or (2) CaCO3 dissolution that occurred before lithification (i.e., in the water column or at the seafloor).
{"title":"Nannofossil imprints across the Paleocene-Eocene thermal maximum","authors":"S. Slater, Paul R. Bown, Phillip E. Jardine","doi":"10.1130/g51746.1","DOIUrl":"https://doi.org/10.1130/g51746.1","url":null,"abstract":"The Paleocene–Eocene thermal maximum (PETM; ca. 56 Ma) geological interval records a marked decline in calcium carbonate (CaCO3) in seafloor sediments, potentially reflecting an episode of deep- and possibly shallow-water ocean acidification. However, because CaCO3 is susceptible to postburial dissolution, the extent to which this process has influenced the PETM geological record remains uncertain. Here, we tested for evidence of postburial dissolution by searching for imprint fossils of nannoplankton preserved on organic matter. We studied a PETM succession from the South Dover Bridge (SDB) core, Maryland, eastern United States, and compared our imprint record with previously published data from traditionally sampled CaCO3-preserved nannoplankton body fossils. Abundant imprints through intervals devoid of CaCO3 would signify that postburial dissolution removed much of the CaCO3 from the rock record. Imprints were recorded from most samples but were rare and of low diversity. Body fossils were substantially more numerous and diverse, capturing a more complete record of the living nannoplankton communities through the PETM. The SDB succession records a dissolution zone/low-carbonate interval at the onset of the PETM, through which nannoplankton body fossils are rare. No nannoplankton imprints were found from this interval, suggesting that the rarity of body fossils is unlikely to have been the result of postburial dissolution. Instead, our findings suggest that declines in CaCO3 through the PETM at the SDB location were the result of: (1) biotic responses to changes that were happening during this event, and/or (2) CaCO3 dissolution that occurred before lithification (i.e., in the water column or at the seafloor).","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139809360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Global compilations of zircon geochemistry have been used as evidence for changes in plate tectonic styles and surface environments. In particular, zircon δ18O has been used as a proxy for global sediment subduction and incorporation into igneous melts. However, research employing such compilations commonly ignores geologic and geographic context. We analyze a newly georeferenced zircon δ18O database from 1000 Ma to present. The compilation shows positive and negative isotopic excursions, both of which have been interpreted in the context of global phenomena. Sensitivity testing demonstrates that these excursions are the product of regional tectonic environments. Specifically, low Tonian–Cryogenian δ18O, previously interpreted as a climate signal of snowball Earth glacial meltwater, is isolated to ultra-high-pressure rocks of the Dabie Sulu orogen in central Asia, ophiolites in Egypt, and juvenile arc development in Madagascar, predating Cryogenian glaciation. Positive anomalies in the Ediacaran–Cambrian and Devonian, previously interpreted to record snowball Earth erosion and the rise of land plants, are the result of upper-plate, supracrustal sources of Gondwana. A Neogene anomaly is the result of volcanic rocks associated with Yellowstone and Iceland. Sampling bias in zircon geochemical compilations is analogous to that of Lagerstätten (sites of exquisite fossil preservation) and the “monograph effect” (large contributions from individual researchers) in paleontology, which both result in artifacts of over-representation. Long-term zircon δ18O trends broadly track the generation of collisional granites and continental arcs through time, recording the melting of sediments and sedimentary rocks in individual orogens, and not variations in sediment subduction globally.
锆石地球化学的全球汇编被用作板块构造样式和地表环境变化的证据。特别是，锆石δ18O 被用作全球沉积物俯冲和融入火成岩熔体的替代物。然而，采用此类汇编的研究通常会忽略地质和地理背景。我们分析了从 1000 Ma 到现在的最新地理参照锆石 δ18O 数据库。该汇编显示了正负同位素偏移，这两种偏移都被解释为全球现象。敏感性测试表明，这些偏移是区域构造环境的产物。具体来说，以前被解释为雪球地球冰川融水气候信号的托尼-冷元古代低δ18O，被隔离到中亚大别苏禄造山带的超高压岩石、埃及的蛇绿岩和马达加斯加的幼弧发育中，早于冷元古代冰川。埃迪卡拉-寒武纪和泥盆纪的正异常以前被解释为记录了雪球地球的侵蚀和陆地植物的兴起，是冈瓦纳上板块超地壳源的结果。新近纪异常是与黄石公园和冰岛有关的火山岩造成的。锆石地球化学资料汇编中的取样偏差类似于古生物学中的 Lagerstätten（化石保存完好的地点）和 "专著效应"（个别研究人员的大量贡献），两者都会造成过度代表性的假象。锆石δ18O的长期趋势大致跟踪了碰撞花岗岩和大陆弧的生成过程，记录了各个造山运动中沉积物和沉积岩的熔化过程，而不是全球范围内沉积物俯冲的变化。
{"title":"Does zircon geochemistry record global sediment subduction?","authors":"K. Sundell, F. A. Macdonald, Stephen J. Puetz","doi":"10.1130/g51817.1","DOIUrl":"https://doi.org/10.1130/g51817.1","url":null,"abstract":"Global compilations of zircon geochemistry have been used as evidence for changes in plate tectonic styles and surface environments. In particular, zircon δ18O has been used as a proxy for global sediment subduction and incorporation into igneous melts. However, research employing such compilations commonly ignores geologic and geographic context. We analyze a newly georeferenced zircon δ18O database from 1000 Ma to present. The compilation shows positive and negative isotopic excursions, both of which have been interpreted in the context of global phenomena. Sensitivity testing demonstrates that these excursions are the product of regional tectonic environments. Specifically, low Tonian–Cryogenian δ18O, previously interpreted as a climate signal of snowball Earth glacial meltwater, is isolated to ultra-high-pressure rocks of the Dabie Sulu orogen in central Asia, ophiolites in Egypt, and juvenile arc development in Madagascar, predating Cryogenian glaciation. Positive anomalies in the Ediacaran–Cambrian and Devonian, previously interpreted to record snowball Earth erosion and the rise of land plants, are the result of upper-plate, supracrustal sources of Gondwana. A Neogene anomaly is the result of volcanic rocks associated with Yellowstone and Iceland. Sampling bias in zircon geochemical compilations is analogous to that of Lagerstätten (sites of exquisite fossil preservation) and the “monograph effect” (large contributions from individual researchers) in paleontology, which both result in artifacts of over-representation. Long-term zircon δ18O trends broadly track the generation of collisional granites and continental arcs through time, recording the melting of sediments and sedimentary rocks in individual orogens, and not variations in sediment subduction globally.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139869425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Global compilations of zircon geochemistry have been used as evidence for changes in plate tectonic styles and surface environments. In particular, zircon δ18O has been used as a proxy for global sediment subduction and incorporation into igneous melts. However, research employing such compilations commonly ignores geologic and geographic context. We analyze a newly georeferenced zircon δ18O database from 1000 Ma to present. The compilation shows positive and negative isotopic excursions, both of which have been interpreted in the context of global phenomena. Sensitivity testing demonstrates that these excursions are the product of regional tectonic environments. Specifically, low Tonian–Cryogenian δ18O, previously interpreted as a climate signal of snowball Earth glacial meltwater, is isolated to ultra-high-pressure rocks of the Dabie Sulu orogen in central Asia, ophiolites in Egypt, and juvenile arc development in Madagascar, predating Cryogenian glaciation. Positive anomalies in the Ediacaran–Cambrian and Devonian, previously interpreted to record snowball Earth erosion and the rise of land plants, are the result of upper-plate, supracrustal sources of Gondwana. A Neogene anomaly is the result of volcanic rocks associated with Yellowstone and Iceland. Sampling bias in zircon geochemical compilations is analogous to that of Lagerstätten (sites of exquisite fossil preservation) and the “monograph effect” (large contributions from individual researchers) in paleontology, which both result in artifacts of over-representation. Long-term zircon δ18O trends broadly track the generation of collisional granites and continental arcs through time, recording the melting of sediments and sedimentary rocks in individual orogens, and not variations in sediment subduction globally.
锆石地球化学的全球汇编被用作板块构造样式和地表环境变化的证据。特别是，锆石δ18O 被用作全球沉积物俯冲和融入火成岩熔体的替代物。然而，采用此类汇编的研究通常会忽略地质和地理背景。我们分析了从 1000 Ma 到现在的最新地理参照锆石 δ18O 数据库。该汇编显示了正负同位素偏移，这两种偏移都被解释为全球现象。敏感性测试表明，这些偏移是区域构造环境的产物。具体来说，以前被解释为雪球地球冰川融水气候信号的托尼-冷元古代低δ18O，被隔离到中亚大别苏禄造山带的超高压岩石、埃及的蛇绿岩和马达加斯加的幼弧发育中，早于冷元古代冰川。埃迪卡拉-寒武纪和泥盆纪的正异常以前被解释为记录了雪球地球的侵蚀和陆地植物的兴起，是冈瓦纳上板块超地壳源的结果。新近纪异常是与黄石公园和冰岛有关的火山岩造成的。锆石地球化学资料汇编中的取样偏差类似于古生物学中的 Lagerstätten（化石保存完好的地点）和 "专著效应"（个别研究人员的大量贡献），两者都会造成过度代表性的假象。锆石δ18O的长期趋势大致跟踪了碰撞花岗岩和大陆弧的生成过程，记录了各个造山运动中沉积物和沉积岩的熔化过程，而不是全球范围内沉积物俯冲的变化。
{"title":"Does zircon geochemistry record global sediment subduction?","authors":"K. Sundell, F. A. Macdonald, Stephen J. Puetz","doi":"10.1130/g51817.1","DOIUrl":"https://doi.org/10.1130/g51817.1","url":null,"abstract":"Global compilations of zircon geochemistry have been used as evidence for changes in plate tectonic styles and surface environments. In particular, zircon δ18O has been used as a proxy for global sediment subduction and incorporation into igneous melts. However, research employing such compilations commonly ignores geologic and geographic context. We analyze a newly georeferenced zircon δ18O database from 1000 Ma to present. The compilation shows positive and negative isotopic excursions, both of which have been interpreted in the context of global phenomena. Sensitivity testing demonstrates that these excursions are the product of regional tectonic environments. Specifically, low Tonian–Cryogenian δ18O, previously interpreted as a climate signal of snowball Earth glacial meltwater, is isolated to ultra-high-pressure rocks of the Dabie Sulu orogen in central Asia, ophiolites in Egypt, and juvenile arc development in Madagascar, predating Cryogenian glaciation. Positive anomalies in the Ediacaran–Cambrian and Devonian, previously interpreted to record snowball Earth erosion and the rise of land plants, are the result of upper-plate, supracrustal sources of Gondwana. A Neogene anomaly is the result of volcanic rocks associated with Yellowstone and Iceland. Sampling bias in zircon geochemical compilations is analogous to that of Lagerstätten (sites of exquisite fossil preservation) and the “monograph effect” (large contributions from individual researchers) in paleontology, which both result in artifacts of over-representation. Long-term zircon δ18O trends broadly track the generation of collisional granites and continental arcs through time, recording the melting of sediments and sedimentary rocks in individual orogens, and not variations in sediment subduction globally.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139809744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Paleocene–Eocene thermal maximum (PETM; ca. 56 Ma) geological interval records a marked decline in calcium carbonate (CaCO3) in seafloor sediments, potentially reflecting an episode of deep- and possibly shallow-water ocean acidification. However, because CaCO3 is susceptible to postburial dissolution, the extent to which this process has influenced the PETM geological record remains uncertain. Here, we tested for evidence of postburial dissolution by searching for imprint fossils of nannoplankton preserved on organic matter. We studied a PETM succession from the South Dover Bridge (SDB) core, Maryland, eastern United States, and compared our imprint record with previously published data from traditionally sampled CaCO3-preserved nannoplankton body fossils. Abundant imprints through intervals devoid of CaCO3 would signify that postburial dissolution removed much of the CaCO3 from the rock record. Imprints were recorded from most samples but were rare and of low diversity. Body fossils were substantially more numerous and diverse, capturing a more complete record of the living nannoplankton communities through the PETM. The SDB succession records a dissolution zone/low-carbonate interval at the onset of the PETM, through which nannoplankton body fossils are rare. No nannoplankton imprints were found from this interval, suggesting that the rarity of body fossils is unlikely to have been the result of postburial dissolution. Instead, our findings suggest that declines in CaCO3 through the PETM at the SDB location were the result of: (1) biotic responses to changes that were happening during this event, and/or (2) CaCO3 dissolution that occurred before lithification (i.e., in the water column or at the seafloor).
{"title":"Nannofossil imprints across the Paleocene-Eocene thermal maximum","authors":"S. Slater, Paul R. Bown, Phillip E. Jardine","doi":"10.1130/g51746.1","DOIUrl":"https://doi.org/10.1130/g51746.1","url":null,"abstract":"The Paleocene–Eocene thermal maximum (PETM; ca. 56 Ma) geological interval records a marked decline in calcium carbonate (CaCO3) in seafloor sediments, potentially reflecting an episode of deep- and possibly shallow-water ocean acidification. However, because CaCO3 is susceptible to postburial dissolution, the extent to which this process has influenced the PETM geological record remains uncertain. Here, we tested for evidence of postburial dissolution by searching for imprint fossils of nannoplankton preserved on organic matter. We studied a PETM succession from the South Dover Bridge (SDB) core, Maryland, eastern United States, and compared our imprint record with previously published data from traditionally sampled CaCO3-preserved nannoplankton body fossils. Abundant imprints through intervals devoid of CaCO3 would signify that postburial dissolution removed much of the CaCO3 from the rock record. Imprints were recorded from most samples but were rare and of low diversity. Body fossils were substantially more numerous and diverse, capturing a more complete record of the living nannoplankton communities through the PETM. The SDB succession records a dissolution zone/low-carbonate interval at the onset of the PETM, through which nannoplankton body fossils are rare. No nannoplankton imprints were found from this interval, suggesting that the rarity of body fossils is unlikely to have been the result of postburial dissolution. Instead, our findings suggest that declines in CaCO3 through the PETM at the SDB location were the result of: (1) biotic responses to changes that were happening during this event, and/or (2) CaCO3 dissolution that occurred before lithification (i.e., in the water column or at the seafloor).","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139869030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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