Browsing by Author "Klaus, James"

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    Early to Middle Miocene shallow-water corals from La Guajira, Colombia
    (2016) Flórez, Paola; Zapata Ramírez, Paula Andrea; Jaramillo, Carlos; Klaus, James
    Here we describe and illustrate 31 Miocene corals species from the Siamaná and Jimol Formations that were collected over two expeditions in the Guajira basin, Colombia during 2011 and 2014. Corals include 25 species, derived from 15 different genera and 12 families. Six of them remain with open nomenclature. From the 25 species found in the study area, 88% are extinct and the remaining under endanger status. Most of the species are hermatypic components of the Scleractinian order, with the exception of a member of the Milleporidae family. The corals described are composed of typical taxa from the Oligocene-Miocene transition, during which they were important components in building fringing and patch reefs in the circum- Caribbean/Gulf of Mexico region. The presence of typical Oligocene coral taxa such as Agathiphyllia spp., Antiguastrea sp., and Diploastrea spp. from La Guajira extend the distribution of these genera into the Miocene, adding a more recent geological presence in the Southern Caribbean. Coral assemblages suggest a development in clear, calm and shallow waters, under oligotrophic conditions and only moderate physical disturbance. Our descriptions represent the first effort to characterize the taxonomy of fossilized corals in Colombia.
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    Reef development during the Oligo-Miocene transition: A new Aquitanian record from Guajira Colombia
    (2016) Zapata Ramírez, Paula Andrea; Flórez, Paola; Klaus, James
    Caribbean Coral reefs experienced important changes at the Oligo-Miocene transition. The record shows a decrease in modern type reefs at the end of the Oligocene, while non-extensive reefs, mostly confined to shallow or siliciclastic dominated environments, were formed during the early Miocene. At the same time, there are several changes in Caribbean Sea environment including tectonic events, ocean circulation, variations in sea level and temperature. To explore the relationship between regional to global environmental factors on coral evolution and carbonate depositional patterns, we evaluated an Early Miocene (Aquitanian) paleo-reef located at the Siamaná Formation in the Guajira Peninsula, Northern Colombia. Furthermore, we compared the reef with updated ages and coral composition at other Caribbean reefs deposited during the same interval. Siamaná reefs are mainly composed of framestones and rudstones constituted by typical corals of the Oligocene – Miocene taxa (e.g. Agathiphyllia sp., Antiguastrea sp., Diploastrea spp., Siderastrea siderea), most of them in life position forming well consolidated fringing reefs systems with almost 400 m of extension. Comparison with analogous assemblages indicates deposition in similar conditions reported from late Oligocene reefs, but no decrease in coral diversity and/or reduction of the building capacity during the early Miocene were found. Thin sections and total carbon contents analysis also shows absence of siliciclastic input but highest values of carbonate (70.2% to 98%). Results indicate that Siamaná paleo-reef responded to global environmental changes but, their development is also largely controlled by regional patterns where their shallow marine biotas evolved independently. Siamaná collapse is related to a rapid increase in relative sea level and to an increase in regional tectonic subsidence at a later stage (Aquitanian and Burdigarian), rather than an increase in sediment supply during the Oligocene-Miocene transition.