Earthworm-produced calcite granules: A new terrestrial palaeothermometer?

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• 作者：Emma A.A. Versteegh ; Stuart Black ; Matthew G. Canti ; Mark E. Hodson
• 刊名：Geochimica et Cosmochimica Acta
• 出版年：15 December, 2013
• 年：2013
• 卷：123
• 期：Complete
• 页码：351-357
• 全文大小：864 K

文摘

In this paper we show for the first time that calcite granules, produced by the earthworm <em>Lumbricus terrestrisem>, and commonly recorded at sites of archaeological interest, accurately reflect temperature and soil water 未¹⁸O values. Earthworms were cultivated in an orthogonal combination of two different (granule-free) soils moistened by three types of mineral water and kept at three temperatures (10, 16 and 20 掳C) for an acclimatisation period of three weeks followed by transfer to identical treatments and cultivation for a further four weeks. Earthworm-secreted calcite granules were collected from the second set of soils. 未¹⁸O values were determined on individual calcite granules (未¹⁸O_c) and the soil solution (未¹⁸O_w). The 未¹⁸O_c values reflect soil solution 未¹⁸O_w values and temperature, but are consistently enriched by 1.51 (卤 0.12)鈥?in comparison to equilibrium in synthetic carbonates. The data fit the equation 1000 ln 伪 = [20.21 卤 0.92] (10³ T^鈭?) 鈭?#xA0;[38.58 卤 3.18] (<em>Rem>² = 0.95; <em>nem> = 96; <em>pem> < 0.0005). As the granules are abundant in modern soils, buried soils and archaeological contexts, and can be dated using U-Th disequilibria, the developed palaeotemperature relationship has enormous potential for application to Holocene and Pleistocene time intervals.