INVESTIGADORES
VACCARI Norberto Emilio
artículos
Título:
Paleoecological dynamics of Furongian (Late Cambrian) trilobite dominated communities from Northwestern Argentina.
Autor/es:
BALSEIRO, D.; WAISFELD, B.G.; VACCARI, N. E
Revista:
PALAIOS
Editorial:
SEPM-SOC SEDIMENTARY GEOLOGY
Referencias:
Lugar: Lawrence; Año: 2011 vol. 26 p. 484 - 499
ISSN:
0883-1351
Resumen:
The CambrianOrdovician boundary interval is a critical moment in the
ecology of trilobite communities. To understand this transition, we
studiedat three different spatial scaleschanges in the structure of
olenid-dominated communities included in the Parabolina fauna, which
flourished in the latest Cambrian, largely storm-dominated, successions of
northwestern Argentina. At the local (,meter) scale, species-poor
communities occur in shoreface deposits. Relatively flat species-abundance
distributions (SADs) and high evenness characterize upper offshore
to offshore transition settings of the early highstand systems tract (HST),
whereas uneven SADs in species-poor communities are typical of the
lower offshore and shelf environments of the transgressive systems tract
(TST). This pattern is unlikely to be caused by a change in time averaging
and is consistent with the intermediate disturbance hypothesis predicting
unimodal diversity gradients. The pattern is thus interpreted to be related
to a trend in intensity and frequency of storm disturbance along local
shallowing-upward gradients. At the regional scale (,100 km), the
diversity trend across the sampled west-east transect is rather variable and
does not match the depth or oxygen-related gradients. At the
biogeographic scale, the patterns of abundance of two key taxa
(Parabolina and Asaphellus) show contrasting abundance and occupancy
patterns between the Cordillera Oriental siliciclastic settings and the more
carbonate-rich settings of Famatina (Argentina) and Oaxaca (Mexico).
The presence of these genera in settings spatially adjacent, but
environmentally different from their preferred habitats can represent a
signature of source-sink dynamics. Low sample evenness values for the
Cordillera Oriental contrast with those of coeval Laurentian communities,
implying that a secular increase in evenness took place earlier in
Laurentia than in Gondwana.