This article was downloaded by: [T&F Internal Users], [Jayne Kay] On: 07 June 2012, At: 01:32 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Palynology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tpal20 A palynological and sequence-stratigraphic study of Santonian–Maastrichtian strata from the Upper Magdalena Valley basin in central Colombia Sandra Garzon a b c , Sophie Warny a b & Philip J. Bart a a LSU Department of Geology and Geophysics, Baton Rouge, Louisiana, 70803, USA b LSU Museum of Natural Science, Baton Rouge, Louisiana, 70803, USA c Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Panama City, Panama Available online: 20 Mar 2012 To cite this article: Sandra Garzon, Sophie Warny & Philip J. Bart (2012): A palynological and sequence-stratigraphic study of Santonian–Maastrichtian strata from the Upper Magdalena Valley basin in central Colombia, Palynology, 36:sup1, 112-133 To link to this article: http://dx.doi.org/10.1080/01916122.2012.675147 PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Palynology Vol. 36, Supplement 1, 2012, 112–133 A palynological and sequence-stratigraphic study of Santonian–Maastrichtian strata from the Upper Magdalena Valley basin in central Colombia Sandra Garzona,b,c*, Sophie Warnya,b* and Philip J. Barta aLSU Department of Geology and Geophysics, Baton Rouge, Louisiana 70803, USA; bLSU Museum of Natural Science, Baton Rouge, Louisiana 70803, USA; cSmithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Anco´n, Panama City, Panama This paper presents a sequence-stratigraphic interpretation from the palynological analysis and lithologic data of two outcrop sections on the NE flank of the Upper Magdalena Valley (UMV) basin primarily comprising the Santonian–Lower Maastrichtian interval. Important stratal horizons are identified in the northeastern part of the UMV basin and ages assigned to them. A cyclic pattern of palynomorph distribution was recognized in both sections and tied to the different stages of the stratigraphic chart. Spikes in abundance of spores accompanied by pollen characterize the lowstand systems tracts and are replaced by the occurrence of euryhaline dinoflagellate cysts (ceratioids and/or gymnodinioids) during the subsequent transgressive phase. Maximum flooding surfaces (MFS) are recognized by a sudden increase in open marine palynomorphs (peridinioids and/or gonyaulacoids) and the scarcity of terrestrial representatives. As sea level starts to fall, the gradual decrease in open marine dinoflagellates along with the occurrence of euryhaline dinoflagellate cysts and terrestrial representatives corresponds to highstand systems tracts. The sequence-stratigraphic interpretation from palynological analysis was correlated to the global sea-level curve allowing the identification of the Santonian–Campanian and Campanian–Maastrichtian boundaries. System tracts from supercycles ZC-3, ZC-4 and TA-1 were recognized from the palynological data. Keywords: Campanian; dinoflagellate cysts; Maastrichtian; pollen; Santonian; sequence stratigraphy; spores 1. Introduction However, identifying maximum flooding surfaces and Late Cretaceous global sea-level fluctuations generated sequence boundaries can be quite difficult in certain geological surfaces that constitute important correla- settings; for example, different system tracts of the tion horizons in Cretaceous oil-producing basins from sequence may be represented by monotonous fine- northwest South America. Various authors have grained deposits. This is potentially the case with the discussed the synchronous character of these horizons Upper Cretaceous units from the northeastern part of (e.g. Pocknall et al. 1997; Helenes and Somoza 1999; the UMV basin, where the fine-grained lithology and Guerrero et al. 2000; Vallejo 2002; Jaillard et al. 2005). the scarcity of well-preserved calcareous microfossils in In Colombia, a number of studies (e.g. Vergara and certain intervals limit traditional sequence-strati- Rodriguez 1997; Villamil 1998; Guerrero 2002) have graphic interpretations. If present, organic-walled provided a sequence-stratigraphic framework for microfossils (dinoflagellate cysts, spores and pollen) Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012 Cretaceous sequences of the Eastern Cordillera, may constitute an important tool to overcome this Catatumbo, Llanos Foothills and Upper Magdalena problem as the combined lithological/palynological Valley (UMV) basins. The synchronicity of sea-level approach can provide a way to refine the sequence- fluctuations in the UMV basin has been extensively stratigraphic interpretation. Jaramillo and Yepes analyzed (e.g. Guerrero and Sarmiento 1996; Villamil (1994), Guerrero and Sarmiento (1996) and Yepes 1998) and important boundaries including the Santo- (2001) have described palynomorph-rich intervals from nian–Campanian and the Campanian–Maastrichtian Upper Cretaceous UMV strata; however, despite the have been identified from sequence-stratigraphic ana- well-known occurrence of diverse palynomorph assem- lysis and correlated with eustatic changes (Guerrero blages in the area, their application as a tool for et al. 2000). sequence-stratigraphic interpretation has rarely been Sequence-stratigraphic interpretations are com- fully explored. monly based on stacking patterns and lithological Sequence-stratigraphic interpretations based on changes, together with marine fossil abundances. palynological analysis have proven to be effective in *Corresponding authors. Email: [email protected]; [email protected] ISSN 0191-6122 print/ISSN 1558-9188 online Ó 2012 AASP – The Palynological Society http://dx.doi.org/10.1080/01916122.2012.675147 http://www.tandfonline.com Palynology 113 different geographic regions and time intervals. Several calcareous black shales; the upper Lidita Formation studies have established the direct relationship between consists of siliceous mudstones and black cherts; and the palynological record and sea-level fluctuations (e.g. the Buscavidas Formation is characterized by calcar- Poumot 1989; Gregory and Hart 1992; Li and Habib eous gray mudstones interbedded with limestones and 1996; Holz and Dias 1998; Rull 2000, 2002). Poumot calcareous shales. (1989) was the first to tie cyclic patterns of terrestrial palynomorph distribution on tropical coastal settings to a sequence-stratigraphic framework. He correlated 3. Methods palynological assemblages dominated by fern spores Two outcrop sections were measured. The Aico Creek and forest pollen to the lowstand, higher abundances section, located at 38 440 N and 758 230 W, comprises of palm pollen to early sea-level rise and an increase of from base to top the lower Lidita Formation, El Cobre mangrove pollen to the later transgressive phase. Formation, upper Lidita Formation and Buscavidas Poumot (1989) explained these fluctuations of pollen Formation (Figure 2). The Buitrera Creek section, and spore assemblage composition on grounds of the located at 48 300 N and 748 370 W, is composed of the environmental preferences of the parent plants and uppermost part of the El Cobre Formation, the upper palynomorph transport. A similar pattern was de- Lidita Formation and the Buscavidas Formation scribed by Gregory and Hart (1992) who noticed that (Figure 2). Both sections were previously studied by during lowstand deposition, palynological assemblages Jaramillo and Yepes (1994) and Yepes (2001). Accord- were dominated by terrestrial palynomorphs produced ing to these previous studies, the Aico Creek section by both hydrophilic and xerophilic plants; highstand comprises sediments of Coniacian–Early Maastrich- deposition was however characterized by an increase of tian age and the Buitrera Creek section includes palynomorphs derived from hydrophilic plants only. sediments of Campanian–Early Maastrichtian age. In another study, Holz and Dias (1998) reported high Ninety palynological samples were analyzed. All spore content in lowstand system tracts and a samples were treated with hydrochloric and hydro- gradually decreasing trend in spore abundance in fluoric acids. Following these steps, centrifuging in transgressive systems tracts. The environmental pre- heavy liquid (ZnBr2) was used to further separate the ferences of certain groups of marine palynomorphs organic fraction of the samples (Traverse 1988; Brown also provide valuable information on sea-level changes 2008). Up to 300 palynomorphs were counted per (e.g. Li and Habib 1996; Schioler et al. 1997; Warny sample although, when recovery was extremely