Evidence for vertical motility has been observed among six Campanian deep-water agglutinated foraminiferal species from the Furlo Bentonite in the Umbria-Marche Basin, Ital

Galeotti, S.

Kaminski, M.A..

English

UCL Discovery

104    Micropalaeontological Note    In:  Bubík,  M.  &  Kaminski,  M.A.  (eds),  2004.  Proceedings  of  the  Sixth  International  Workshop  on  Agglutinated Foraminifera. Grzybowski Foundation Special Publication, 8, 104.  Evidence for vertical motility in Campanian deep-water agglutinated foraminifera: The Furlo volcanic ash layer   MICHAEL A. KAMINSKI1 and SIMONE GALEOTTI2  1. Department of Earth Sciences, University College London, Gower Street, London WCIE 6BT, U.K.; and  KLFR, 3 Boyne Avenue, Hendon, London, NW4 2JL, U.K.  2. Istituto di Geologia, Università degli Studi di Urbino, Campus Scientifico, Località Crocicchia, 61029 Urbino, Italy   ABSTRACT Evidence  for  vertical  motility  has  been  observed  among  six  Campanian  deep-water  agglutinated foraminiferal species from the Furlo Bentonite in the Umbria-Marche Basin, Italy.   INTRODUCTION Modern agglutinated foraminifera inhabit a variety of habitats  within  the  sediment  column,  and  some species  have  been  observed  to  burrow  beneath  the sediment  surface  (Kaminski  et  al.,  1988).  Vertical motility among modern agglutinated foraminifera has been observed directly  in experimental studies (e.g., Ernst  et  al.,  2000).  However,  the  phenomenon  of vertical  motility  in  fossil  assemblages  remains  a matter for speculation.  In  this  study,  we  report  evidence  for  vertical motility  among  certain  Campanian  deep-water agglutinated  foraminifera.  Near  the  town  of  Furlo, Italy a 15 cm-thick bentonite layer occurs within the Scaglia Rossa Formation of the Umbria-Marche Basin. The deposition of this volcaniclastic layer caused mass mortality  among  benthic  foraminifera,  and  an interesting  succession  of  recolonisation  assemblages has been documented in the Scaglia limestone directly overlying the bentonite (Galeotti et al., 2000). Previous analysis  failed  to  find  evidence  for  the  presence  of benthic  foraminifera  within  the  bentonite  layer.  For this study, we resampled the basal 3 cm of the Furlo bentonite in an effort to determine whether or not any of  the  benthic  foraminifera  were  able  to  partially exhume  themselves  following  the  deposition  of  the volcanic ash layer.  RESULTS A large sample (ca. 250 g) from the basal portion of the  Furlo  bentonite  was  washed  and  examined  for foraminifera.  Twenty-one  specimens  were  found, belonging  to  six  species:  Glomospira  serpens,  Clavuli-noides subparisiensis, Glomospirella sp., Recurvoides sp., Saccammina sp., and Paratrochamminoides sp. The bulk of the ash layer is barren of foraminifera.  DISCUSSION We believe the DWAF specimens recovered from the basal  portion  of  the  bentonite  attempted  to  actively exhume themselves after being buried by over 15 cm of volcanic ash. We exclude the possibility that these specimens  were  mixed  upward  by  bioturbation, because we did not find any specimens of planktonic foraminifera in our sample. Beneath the Furlo bento-nite the P/B ratio in the Scaglia Rossa is very high (ca. 99%), and if our specimens were passively mixed into the  ash  we  would  expect  to  find  numerous planktonics. Furthermore, the bulk of the agglutinated assemblage beneath the ash consists of tubular forms such as Rhizammina. These were absent in our sample.  The finding of specimens that mostly belonging to tapered,  elongate  morphotypes  such  as  Glomospira serpens  and  Clavulinoides  subparisiensis  confirms  our prior  assumptions  about  the  link  between  morphol-ogy and life position. The tapered elongate forms are presumed  to  live  in  a  deeper  infaunal  habitat,  and possess  the  optimal  shape  for  burrowing  activity. Glomospirids and Saccammina are assumed to occupy a shallow infaunal habitat, and actively crawl beneath the sediment surface.  Motility has been observed in living specimens of Ammodiscus.  Our  findings  confirm  observations  of  Hess  & Kuhnt  (1996),  who  found  Rose  Bengal  stained agglutinated foraminifera in the basal portion of the 1991 Mt. Pinatubo ash layer in the South China Sea. These authors found that within three years following the  depostion  of  the  ash,  certain  species  of  DWAF were able to crawl upwards 1-2 cm into the ash layer. The reason for this vertical motility may be to escape oxygen  depletion  beneath  the  volcanic  ash  layer,  as benthic  organisms  consumed  the  oxygen  in  pore waters. However, in both the modern and Campanian examples,  the  ability  of  the  foraminifera  to  exhume themselves is apparently limited, and the deposition of more than about two cm of volcanic ash results in total mass mortality among the benthic foraminiferal fauna.   REFERENCES Hess, S. & Kuhnt, W., 1996. Deep-sea benthic foraminiferal recolonization  of  the  1991  Mt.  Pinatubo  ash  layer  in  the South China Sea. Marine Micropaleontology, 28, 171-197. Kaminski,  M.A,  Grassle,  J.F.  &  Whitlatch,  R.B.,  1988.  Life history  and  recolonization  among  agglutinated  fora-minifera  in  the  Panama  Basin.  Abhandlungen  der  Geolo-gischen Bundesanstalt, 41, 229-244. Galeotti, S., Bellagamba, M., Kaminski, M.A. & Montanari, A.  2002.  Deep-sea  benthic  foraminiferal  recolonisation following a volcaniclastic event in the lower Campanian of the  Scaglia  Rossa  Formation  (Umbria-Marche  Basin, central Italy). Marine Micropaleontology, 44, 57-76.  

Deep-sea benthic foraminiferal recolonisation following a volcaniclastic event in the lower Campanian of the Scaglia Rossa Formation (Umbria-Marche Basin, central Italy).

Evidence for vertical motility in Campanian deep-water agglutinated foraminifera: The Furlo volcanic ash layer

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