Rock-magnetic properties of the Cretaceous/Tertiary Micara Formation in the Guantánamo area, eastern Cuba
Initial results of a rock-magnetic study of the 35 m thick Calabazas sedimentary section of the Micara Formation, easternCuba are reported. Previous studies have interpreted the Cretaceous/Tertiary (K/T) boundary within the Micara Formation, basedmainly on analyses of planktonic foraminifera assembl...
| Autores: | , , |
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| Formato: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 1998 |
| País: | México |
| Recursos: | Universidad Nacional Autónoma de México |
| Repositorio: | Redalyc-UNAM |
| OAI Identifier: | oai:redalyc.org:56837401 |
| Acesso em linha: | https://www.redalyc.org/articulo.oa?id=56837401 |
| Access Level: | acceso abierto |
| Palavra-chave: | Ciencias de la Tierra Rock Cuba Paleocene Cretaceous Micara Formation |
| Resumo: | Initial results of a rock-magnetic study of the 35 m thick Calabazas sedimentary section of the Micara Formation, easternCuba are reported. Previous studies have interpreted the Cretaceous/Tertiary (K/T) boundary within the Micara Formation, basedmainly on analyses of planktonic foraminifera assemblages and lateral correlations. The K/T boundary in sedimentary sections inGubbio, Italy and Caravaca, Spain is characterized, in addition to the iridium anomaly, by a rock-magnetic anomaly that is relatedto enrichment of iron oxide minerals (magnetite). Study of rock-magnetic properties in the Calabazas section identifies threehorizons characterized by increased abundance of magnetic minerals, which are located at about 4, 12 and 20 m above the base ofthe outcrop, respectively. The 4 m horizon is characterized by magnetic susceptibility values of about 90 x 10-5 SI, whereas in therest of the section values are around 20 x 10-5 SI. The corresponding NRM and IRM intensities are about 7 mA/m and 7 A/m,respectively. The 12 m horizon is marked by 22 A/m IRM intensity and 14 mA/m NRM intensity. The 20 m horizon is marked by16 mA/m NRM intensity and 3 A/m IRM intensity. The magnetic anomaly at 4 m corresponds to the highest concentration ofmagnetic minerals, likely iron-rich fine-grained magnetites with pseudo-single domain behavior. However, this magnetic anomalyin the Calabazas section displays a wider stratigraphic range than in other K/T boundary sections. The characteristics of the widemagnetic anomaly suggest an alternative interpretation in terms of sedimentary input of magnetic material not related to the hotearly impact ejecta. The Calabazas section lies in the Paleocene, and the magnetic peaks observed in the sediments result fromfluctuations in the relative contents of magnetic minerals. |
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