Three Holocene tufas from Gran Canaria volcanic island were studied with the aim of deciphering their sedimentary evolution through space and time. Las Temisas tufa (south-eastern arid part of the island) is dominantly composed of oncoids, intraclasts, phytoclasts, coated stems, minor thin stromatolites, and a high amount of siliciclastics. It was deposited in a fluvial system with variable flow velocities and palustrine conditions areas, which alternated with high energy events. Azuaje tufa (northern humid part of the island) is composed of coated stems, stromatolites, oncoids and phytoclasts, with relatively low amounts of siliciclastics, suggesting slow-flowing and palustrine conditions and a relatively low incidence of (high energy) floodings. Los Berrazales tufa (north-west of Gran Ganaria, the most humid one), is mainly composed of coated stems and crystalline crusts, formed in a laminar flow regime. Dominant clastic sedimentation in Las Temisas and high calcite growth rates in Los Berrazales led to a poor development of stromatolites in comparison with Azuaje. Las Temisas and Azuaje deposits have similar upward evolution with decreasing trend in siliciclastics and increasing trend in carbonates. However, Las Temisas has higher siliciclastic and lower phytoclastic contents suggesting a less vegetated area and more arid climate than in the other deposits. Additionally, tufas record local events common in volcanic terrains. Azuaje presents three units bounded by erosive discontinuities, which reveal significant erosion by enhanced runoff that could be caused by loss of vegetation due to wildfires related to volcanic eruptions at headwaters. Las Temisas record a possible interruption in sedimentation represented by aligned boulders due to rockfalls from the hillsides. These deposits formed from waters with similar chemistry providing to the carbonates their similar signals in δ¹³C–δ¹⁸O stable isotopes and ⁸⁷Sr/⁸⁶Sr ratios like that of the volcanic rocks. This work shows how, in volcanic areas, tufas are unique archives of the climate, vegetation and volcanic-related processes, because all imprint the sedimentary regime of tufa deposition.

中文翻译：

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碳酸盐凝灰岩作为火山环境中气候和沉积动力学的档案，来自大加那利岛（西班牙）的例子

研究了来自大加那利岛火山岛的三个全新世凝灰岩，目的是破译它们在空间和时间上的沉积演化。Las Temisas tufa（该岛的东南部干旱地区）主要由类球状体、碎屑内、植骨破碎、覆膜茎、少量薄叠层石和大量硅质碎屑组成。它沉积在具有可变流速和湖泊条件区域的河流系统中，这些区域与高能量事件交替出现。Azuaje tufa（该岛北部潮湿的部分）由被覆茎、叠层石、瘤状体和植株碎屑组成，硅质碎屑含量相对较低，这表明流动缓慢和沼泽条件以及（高能量）洪水的发生率相对较低。Los Berrazales tufa（格兰加纳里亚西北部，最潮湿的地区），主要由被覆茎和结晶壳组成，形成层流状态。与 Azuaje 相比，Las Temisas 的主要碎屑沉积和 Los Berrazales 的高方解石生长率导致叠层石的发育不良。Las Temisas 和 Azuaje 矿床具有相似的上升演化趋势，硅质碎屑岩呈下降趋势，碳酸盐岩呈上升趋势。然而，与其他矿床相比，Las Temisas 具有较高的硅质碎屑和较低的植物碎屑含量，表明植被面积较少，气候更加干旱。此外，凝灰岩记录了火山地形中常见的局部事件。Azuaje 展示了三个以侵蚀不连续性为边界的单元，这表明径流增加可能是由于与源头火山喷发相关的野火导致植被损失造成的严重侵蚀。Las Temisas 记录了由于山坡上的落石而导致的以对齐的巨石为代表的沉积可能中断。这些沉积物由具有相似化学性质的水形成，为碳酸盐提供了相似的 δ 信号¹³ C–δ ¹⁸ O 稳定同位素和⁸⁷ Sr/ ⁸⁶ Sr 比值与火山岩相似。这项工作表明，在火山地区，凝灰岩是气候、植被和火山相关过程的独特档案，因为所有这些都印有凝灰岩沉积的沉积制度。