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Alegret, Ortiz & Kaminski (eds.), 2012. Ninth International Workshop on Agglutinated Foraminifera, Abstract Volume
What caused the Glomospira acme during the earliest Eocene?
Gabriela de Jesús ARREGUÍN-RODRÍGUEZ 1 , Laia ALEGRET 1,2 and Silvia ORTIZ 3
1 Departamento de Ciencias de la Tierra, Facultad de Ciencias, Universidad de Zaragoza, 50009
Zaragoza, Spain.
2 Instituto Universitario de Investigación en Ciencias Ambientales de Aragón. Universidad de
Zaragoza, 50009 Zaragoza, Spain.
3 Departamento de Estratigrafía y Paleontología, Facultad de Ciencia y Tecnología, Universidad del
País Vasco, 48940, Leioa, Spain.
e-mail: gjarreguin@gmail.com
The Paleocene-Eocene Thermal Maximum (PETM) event, ~55.5 Ma ago, is characterized by
globally elevated temperatures, a negative δ 13 C excursion and major biotic changes on land
and in the oceans. Deep-sea benthic foraminifera suffered the most important extinction in the
Cenozoic, with 35-55% of the species disappearing at the Paleocene-Eocene boundary
(Thomas, 2007; Alegret et al., 2010).
After the extinction of deep-sea benthic foraminifera, some agglutinated disaster or
opportunistic taxa bloomed. The proliferation of species of the genera Glomospira (Rzehak),
Glomospirella (Plummer) and Repmanina (Suleymanov) is commonly known as the
“Glomospira acme” (Kaminski and Gradstein, 2005). Such proliferation has been traditionally
associated with a widespread rise of the carbonate compensation depth (CCD) that took place
during the PETM (Kaminski and Gradstein, 2005). However, dissolution experiments showed
that the absolute abundance of the genera Glomospira, Glomospirella and Repmanina was
independent from the %CaCO3 content and the degree of dissolution (Alegret et al., 2010),
suggesting that there must have been a paleoenvironmental control of the Glomospira acme.
An analysis of the paleogeographical distribution of the proliferation of Glomospira spp.
during the earliest Eocene allowed us to assess the paleoenvironmental conditions that may
have controlled the proliferation of these taxa.
The earliest Eocene Glomospira acme at NP9, P5 and E1 biozones occurs in the
Tethys region and in the North Atlantic Ocean, including Contessa section in Italy (Galeotti et
al., 2004; Giusberti et al., 2009), Polish Outer Carpathians (Morgiel and Olszewska, 1981;
Bąk, 2004), Romanian Straja section in the Eastern Carpathians (Bindiu and Filipescu, 2011),
Anthering and Untersberg sections in Austria (Egger et al., 2003, 2005), Trabakua Pass and
Alamedilla sections in Spain (Coccioni et al, 1994; Alegret et al., 2010), and the Iberian
Abyssal Plain (Kuhnt and Collins, 1996). Considering the paleoenvironmental conditions at
these locations, the Glomospira acme was independent from surface primary productivity and
oxygenation of the sea-bottom waters. It is unlikely that the paleolatitude had any influence
on the Glomospira acme, although further studies should investigate possible differences in
extinction rates and availability of empty ecological niches at different latitudes. The
relationship between any source of isotopically light carbon and the abundance of Glomospira
is still subject of study.
On the other side, the input of refractory organic matter through sporadic pulses of
terrigenous or siliciclastic material may have stimulated the Glomospira acme. These inputs
were the result of continental silicate weathering due to the intensification of the hydrologic
cycle during the PETM (Dickens et al., 2003). The increased flux of refractory organic matter
to the seafloor may have provided an alternative food source for some benthic species that
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