Taxonomic fidelity of silicified filamentous microbes from hot-spring systems in the Taupo Volcanic Zone, North Island, New Zealand

ABSTRACTModern, silica-precipitating hot springs, like those found in the Taupo Volcanic Zone (TVZ) on the North Island of New Zealand, are natural laboratories for assessing microbial silicification. Many of the silicified microbes found in the siliceous sinters of these spring systems seem to be life-like replicas of the original microbes. Such preservation reflects the fact that many of the microbes are replaced and encrusted by opal-A before they are destroyed by desiccation and decay. The taxonomic fidelity of these silicified microbes depends on the preservation potential of those features which are needed to identify them. For example, identification of extant cyanobacteria, relies on as many as 37 different features, most of which are not preserved by silicification.In the hot-spring systems of the TVZ, characterisation of cyanobacteria which have been replaced and encrusted by opal-A is typically restricted to colony morphology, the length, diameter and morphology of the filament, and the presence/absence of septa, branching or a sheath. In many cases, description is limited to a subset of these parameters. Such a limited set of morphological characteristics severely impedes identifications in terms of extant taxa. The physical changes which accompany the stepwise diagenetic progression from opal-A to opal-CT ± opal-C to microcrystalline quartz may lead to further degradation of the silicified microbes and the loss of more taxonomically important features. Clearly, considerable care must be taken when trying to name silicified microorganisms and make palaeoenvironmental inferences.

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Diagenetic transformations (opal-A to quartz) of low- and mid-temperature microbial textures in siliceous hot-spring deposits, Taupo Volcanic Zone, New Zealand

Canadian Journal of Earth Sciences ◽

10.1139/e03-064 ◽

2003 ◽

Vol 40 (11) ◽

pp. 1679-1696 ◽

Cited By ~ 51

Author(s):

Bridget Y Lynne ◽

Kathleen A Campbell

Keyword(s):

New Zealand ◽

Low Temperature ◽

Hot Spring ◽

Morphological Changes ◽

Taupo Volcanic Zone ◽

Volcanic Zone ◽

Alkali Chloride ◽

Silica Phase ◽

Outflow Channels ◽

Geologic Record

Silica sinter is a subaerial hot-spring deposit formed upon cooling (<100 °C) of discharging alkali-chloride waters. Silica deposition traps and fossilizes living microbes in low-temperature (<35 °C) to mid-temperature (~3559 °C) apronterrace outflow channels and pools, which record distinctive macrotextures and microtextures along a thermal gradient. Sinters from four geothermal fields, Orakei Korako, northern Waiotapu, Te Kopia, and Umukuri, within the Taupo Volcanic Zone, New Zealand, were sampled from two common microbe-rich microfacies (low-temperature palisade, mid-temperature bubble mat) through a range of ages (modern to ~40 000 years BP). We observed morphologic changes in microbial silicification and stepwise transitions in silica phase mineralogy throughout diagenesis (opal-A to quartz). X-ray powder diffractometry analysis of Taupo Volcanic Zone sinter samples revealed that mode of microbial fossilization is controlled by silica phase mineralogy, which also determines the preservation potential of environmentally significant and measurable filament parameters. Typical low-temperature palisade microfacies display thick sheaths (>3 µm diameter) and coarse tubular filament moulds >5 µm in diameter, whereas mid-temperature bubble mat microfacies characteristically consist of thin sheaths (~1 µm diameter) with fine moulds < 3 µm in diameter. Upon diagenesis and silica phase transformation to opal-CT, the two subenvironments cannot be distinguished based on filament diameter alone. This study of recurring microfacies in sinters of different ages allowed us to systematically track the transformation of mineralogical and morphological changes in bioticabiotic depositional elements during diagenesis of silica sinter, and therefore enhance the paleoenvironmental, paleobiological, and paleohydrologic utility of hydrothermal deposits in the geologic record.

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3D Anatomy of a 60-year-old siliceous hot spring deposit at Hipaua-Waihi-Tokaanu geothermal field, Taupo Volcanic Zone, New Zealand

Sedimentary Geology ◽

10.1016/j.sedgeo.2020.105652 ◽

2020 ◽

Vol 402 ◽

pp. 105652 ◽

Cited By ~ 1

Author(s):

Kathleen A. Campbell ◽

Kirsty Nicholson ◽

Bridget Y. Lynne ◽

Patrick R.L. Browne

Keyword(s):

New Zealand ◽

Hot Spring ◽

Geothermal Field ◽

Taupo Volcanic Zone ◽

Volcanic Zone ◽

3D Anatomy

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Hot spring and geyser sinters: the integrated product of precipitation, replacement, and deposition

Canadian Journal of Earth Sciences ◽

10.1139/e03-078 ◽

2003 ◽

Vol 40 (11) ◽

pp. 1549-1569 ◽

Cited By ~ 63

Author(s):

Brian Jones ◽

R W Renaut

Keyword(s):

New Zealand ◽

Hot Spring ◽

Pollen Grains ◽

Taupo Volcanic Zone ◽

Critical Importance ◽

Volcanic Zone ◽

The North ◽

The World ◽

Siliceous Sinter ◽

Flow Through

Complex ornate sinter deposits are found in many hot spring and geysers systems throughout the world, including those located in the Taupo Volcanic Zone on the North Island of New Zealand. Those sinters are formed of opal-A that replaced microbes, opal-A precipitated as cement, accessory minerals (e.g., kaolinite, jarosite, calcite), biological detritus (e.g., leaves, wood, pollen grains), and lithic detritus. The opal-A is compositionally variable because of the amount of water (OH and H2O) and, in some cases, accessory elements (e.g., Au, Ag) bound into its structure. The composition and fabric of the siliceous sinter found at any locality reflect the relative balance among the processes of replacement, precipitation, and deposition. The microbes that inhabit these systems are of critical importance because they are commonly replaced by and (or) encrusted with opal-A. In many settings, copious amounts of opal-A are precipitated as cement around the frameworks of silicified filaments. The cementation process, which continues for as long as waters supersaturated with respect to opal-A flow through the sinter, commonly reduces the porosity of the sinters by as much as 50%. This process is probably of far greater significance than has been previously recognized. The textural and compositional complexity of siliceous sinters found in hot spring and geyser systems reflects the myriad of interrelated processes that control their formation.

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Late Pleistocene siliceous sinter associated with fluvial, lacustrine, volcaniclastic and landslide deposits at Tahunaatara, Taupo Volcanic Zone, New Zealand

Transactions of the Royal Society of Edinburgh Earth Sciences ◽

10.1017/s0263593300000833 ◽

2003 ◽

Vol 94 (4) ◽

pp. 485-501 ◽

Cited By ~ 33

Author(s):

Kathleen A. Campbell ◽

T. F. Buddle ◽

P. R. L. Browne

Keyword(s):

New Zealand ◽

Thermal Regime ◽

Stream Flow ◽

Hot Spring ◽

Taupo Volcanic Zone ◽

Thermal Waters ◽

Thermal Activity ◽

Volcanic Zone ◽

Siliceous Sinter

ABSTRACTThe Tahunaatara sinter, Taupo Volcanic Zone, New Zealand, is a ∼17–20-kyr-old hot-spring deposit of opal-A mineralogy. It is interbedded with fluvial, lacustrine and volcaniclastic sediments, some silicified by infusing thermal waters. The exposed sinter (∼4 m thick, 90 m long) was truncated at its southern margin by a landslide, which deposited a conglomerate (up to 2 m thick, 56 m long) of sinter blocks and associated strata nearby. Kaolinite-rich cobbles at the base of the conglomerate indicate a change in the thermal regime and its probable trigger: acid steamcondensate produced alteration. Clasts in the landslide are oriented SW, the same direction as flattened plant reeds entombed in sinter, and as intercalated fluvial beds. Thus, thermal waters, stream flow and the landslide all likely followed the same palaeo-valley, which is similar in terrain and stratigraphy to the Devonian Rhynie hydrothermal system. The plant-rich, layered, in situ sinter contains fossilised microbes and rare stromatolites, and was deposited on mid- to distal slopes adjacent to marshes. Ash falls, fluvial activity and ponding occurred during and after the thermal activity. Unsilicified tephric Ohakea loess (∼26–17 kyr BP) and Taupo Tephra (1·86 kyr BP) blanket both sinter and landslide. Today, the deposits form resistant remnants in a topographically inverted landscape.

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