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New chronological constraints on intense Holocene eruptions and landslide activity at Tacaná volcanic complex (Mexico)
Quaternary Geochronology ( IF 2.7 ) Pub Date : 2021-04-24 , DOI: 10.1016/j.quageo.2021.101183
Jesús Alcalá-Reygosa , José Luis Arce , José Luis Macías , Irene Schimmelpfennig , Ricardo Saucedo , Juan Manuel Sánchez , Teodoro Carlón , Rosario Vázquez , Guillermo Cisneros-Máximo , Adrian Jímenez , Salvador Fernández , ASTER Team

Usual methods are unfortunately unsuitable to accurately date many Holocene deposits and landforms from active Mexican volcanoes. This is notably the case for the Tacaná Volcanic Complex (TVC), located in the State of Chiapas in southern Mexico, and the San Marcos Department in Guatemala. The complex consists of the Chichuj, Tacaná, and San Antonio volcanoes and the Ardillas dome. Tacaná volcano, the main summit of the TVC, collapsed 15 ± 5 ka ago (40Ar/39Ar), producing the Agua Caliente Debris Avalanche. The result was the formation of a horseshoe-shaped crater 600 m wide open to the northwest. Afterward, several undated effusive and explosive eruptions occurred. All these eruptions are likely Late Pleistocene to Holocene in age because the landforms derived from that activity overlap the horseshoe-shaped crater. To corroborate this hypothesis, we used surface exposure dating with in situ-produced cosmogenic 36Cl combined with lichenometry and dendrochronology in the summit domes, the Ardillas dome, the horseshoe-shaped crater's cliff, and an andesitic lava. The 36Cl exposure ages (9.3 ± 1.9 ka; 8.9 ± 0.9 ka; 8.6 ± 1.7 ka) of the summit domes are statistically indistinguishable within the associated uncertainties and suggest that the domes formed during Early Holocene. Instead, the southern part of the Late Pleistocene collapsed crater yielded significantly younger ages ranging from 5.3 ± 0.6 to 7.0 ± 0.8 ka. These ages are assumed to be minimum and might indicate later rockfall activity and instability, affecting the horseshoe-shaped crater. The 36Cl exposure age of an andesitic lava (0.4 ± 0.1 ka), emplaced to the SW of Tacaná, is in good agreement with lichenometry (>347 yr). These ages could represent a gravitational collapse event associated with phreatic explosions vented close to a scar collapse. The 36Cl exposure ages derived from the Ardillas lava dome (0.3 ± 0.1 ka) do not correspond to its emplacement age. The dome must be older than pyroclastic deposits dated at 760 ± 30 yr BP (14C) that cover its surface. Strikingly, the 36Cl, lichenometrical and dendrochronological data of the “Andesitic” lava and the Ardillas dome are associated with NE-SW landslide scars, explosion craters, phreatic vents, fumarolic activity, and tensional fractures. All these features are perpendicular to the NW-SE minimum stress regime (σ3), affecting the TVC and generating gravitational activity. Nowadays, gravitational collapses represent a real threat to the surrounding populations that can be triggered not only by volcanic activity but also by seismicity and extraordinary rains.



中文翻译:

塔卡纳火山群(墨西哥)对全新世强烈喷发和滑坡活动的新的时间限制

不幸的是,通常的方法不适合准确地确定墨西哥活火山中许多全新世的沉积物和地貌的年代。位于墨西哥南部恰帕斯州的塔卡纳火山综合体(TVC)和危地马拉的圣马科斯系尤其如此。该建筑群包括奇丘伊,塔卡纳和圣安东尼奥火山以及阿迪利亚斯圆顶。塔卡纳(Tacaná)火山是TVC的主要峰顶,在15±5 ka之前坍塌(40 Ar / 39Ar),生产Agua Caliente残骸雪崩。结果是形成了一个向西北宽600 m的马蹄形火山口。之后,发生了几起未注明日期的爆发性和爆发性喷发。所有这些喷发都可能在年龄上是晚更新世至全新世,因为从该活动获得的地貌与马蹄形的火山口重叠。为了证实这一假设,我们在顶峰穹顶,Ardillas穹顶,马蹄形火山口悬崖和安第斯山脉熔岩中使用了表面曝光年代测定法,该方法采用原位产生的宇宙成因36 Cl结合地衣测量法和树木年代学。在36在相关的不确定性范围内,顶峰穹顶的Cl暴露年龄(9.3±1.9 ka; 8.9±0.9 ka; 8.6±1.7 ka)在统计上是无法区分的,表明该穹顶是在全新世早期形成的。取而代之的是,晚更新世南部塌陷的火山口产生了明显年轻的年龄,范围从5.3±0.6到7.0±0.8 ka。这些年龄被认为是最小年龄,可能表明以后的落石活动和不稳定,影响了马蹄形的火山口。Tacaná西南部安山岩熔岩的36 Cl暴露年龄(0.4±0.1 ka)与地衣法(> 347年)非常吻合。这些年龄可能代表引力坍塌事件,这与在疤痕塌陷附近发泄的潜水爆炸有关。在36从Ardillas熔岩穹顶(0.3±0.1 ka)得出的Cl暴露年龄与其放置年龄不符。穹顶必须比覆盖其表面的火山碎屑沉积物(年代为760±30年BP(14 C))更早。令人惊讶的是,“安第斯”熔岩和Ardillas穹顶的36 Cl地衣法和树轮年代学数据与NE-SW滑坡疤痕,爆炸坑,潜水口,富马活动和张性裂缝有关。所有这些特征均垂直于NW-SE最小应力范围(σ3),影响TVC并产生重力活动。如今,引力坍塌对周围人口构成了真正的威胁,不仅是火山活动,而且是地震活动和异常降雨都会引发重力倒塌。

更新日期:2021-05-09
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