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| Titel |
Animal-sediment interactions: the effect of ingestion and excretion by worms on mineralogy |
| VerfasserIn |
S. J. Needham, R. H. Worden, D. McIlroy |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 1, no. 2 ; Nr. 1, no. 2 (2004-11-25), S.113-121 |
| Datensatznummer |
250000136
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| Publikation (Nr.) |
 copernicus.org/bg-1-113-2004.pdf |
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| Zusammenfassung |
| By controlled experiments that simulate marine depositional environments, it
is shown that accelerated weathering and clay mineral authigenesis occur
during the combined process of ingestion, digestion and excretion of
fine-grained sediment by two species of annelid worms. Previously
characterized synthetic mud was created using finely ground, low-grade
metamorphic slate (temperature approximately 300°C) containing highly
crystalline chlorite and muscovite. This was added to experiment and control
tanks along with clean, wind-blown sand. Faecal casts were collected at
regular intervals from the experimental tanks and, less frequently, from the
control tanks. Over a period of many months the synthetic mud (slate) proved
to be unchanged in the control tanks, but was significantly different in
faecal casts from the experimental tanks that contained the worms Arenicola marina and Lumbricus terrestris.
Chlorite was preferentially destroyed during digestion in the gut of A. marina. Both
chlorite and muscovite underwent XRD peak broadening with a skew developing
towards higher lattice spacing, characteristic of smectite formation. A
neoformed Fe-Mg-rich clay mineral (possibly berthierine) and as-yet
undefined clay minerals with very high d-spacing were detected in both A. marina and
L. terrestris cast samples. We postulate that a combination of the low pH and bacteria-rich
microenvironment in the guts of annelid worms may radically accelerate
mineral dissolution and clay mineral precipitation processes during
digestion. These results show that macrobiotic activity significantly
accelerates weathering and mineral degradation as well as mineral
authigenesis. The combined processes of sediment ingestion and digestion
thus lead to early diagenetic growth of clay minerals in clastic sediments. |
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