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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

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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 low, and Wrenn 2002; Warny et al. 2003). tabulation stopped when the full residue was analyzed. In the present study, new palynological data from Identification and description of the palynomorphs two Upper Cretaceous outcrop sections in central was carried out using an Olympus BX 41 transmitted Colombia are analyzed and interpreted within a light microscope at the Center for Excellence in sequence-stratigraphic framework with a view toward Palynology (CENEX), Louisiana State University, understanding the important stratal horizons and Baton Rouge, Louisiana. The results were tabulated determining their respective ages. in Excel spreadsheets and plotted on biostratigraphic distribution charts.

2. Geological setting 3.1. Sequence-stratigraphic analysis using palynology Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012 The UMV is an intermontane basin located in the central part of the Colombian Andes, between the and lithology Eastern and Central cordilleras. The Upper Cretaceous The sequence-stratigraphic interpretations from the units from the northeastern side of the UMV basin Aico Creek and Buitrera Creek sections are based on were deposited in a passive margin setting on inner to the Haq et al. (1987) global sea-level curve plotted outer shelf environments and are dominated by fine- against the Geologic Time Scale of Gradstein et al. grained sediments (Dengo and Covey 1993; figure 1). (2004). The chert unit is interpreted to represent The lithostratigraphic succession of the UMV basin deposition in a more basinal paleoenvironment comprises, from base to top, the lower Lidita Forma- whereas sandstone is interpreted to represent deposition, El Cobre Formation, upper Lidita Formation tion in a more proximal paleoenvironment. Within this and Buscavidas Formation (Figure 2), following the context, the upsection lithologic changes were utilized terminology proposed by Guerrero et al. (2000). In our to infer relative sea-level change. study area, the lower Lidita Formation is characterized Furthermore, distinct palynological assemblages by a succession of siliceous mudstones with inclusions were identified in order to infer sea-level fluctuations of thin phosphatic laminae, cherts and black shales; the and environments of deposition. The assemblages were El Cobre Formation is composed of monotonous grouped by environmental affinities indicative of 114 S. Garzon et al. Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012

Figure 1. Paleogeographic map illustrating the Late Cretaceous depositional setting of the Upper Magdalena Valley Basin (modiﬁed from Dengo and Covey 1993) and the location of the Aico and Buitrera Creek stratigraphic sections. The insert shows the modern geographical location of Colombia. Palynology 115

coastal to open marine depositional conditions and partly supported by previously published studies (e.g. Germeraad et al. 1968; May 1977; Poumot 1989; Gregory and Hart 1992; Schrank 1994; Li and Habib 1996; Holz and Dias 1998; Rull 2000, 2002). Figure 3 illustrates the distribution of the palynological assemblages on a hypothetical onshore–oﬀshore transect and their relation to the sequence-stratigraphic cycle. The composition of the palynological assemblages is presented in Table 1. Several age and environmentally signiﬁcant palynomorphs are illustrated in Plates 1 and 2. Three broad palynological groups are described below.

3.1.1. Marine group In this study, both peridinioid and gonyaulacoid dinoflagellate cysts are interpreted as indicators of open marine environments, although their distribution can be constrained by paleoecological preferences other than distance from shoreline. For instance, peridinioid dinoflagellate cysts possess heterotrophic preferences (Jacobson and Anderson 1986; Powell et al. 1990) and higher abundances are often associated with upwelling events or nearshore environments with high terrigenous input (Bujak 1984; Pearce et al. 2003). Conversely, most gonyaulacoid dinoflagellate cysts are autotrophic (Harland 1988; Powell et al. 1990) and are therefore not constrained by nutrient availability, although certain species of gonyaulacoid dinoflagellate cysts (e.g. some species of Spiniferites)havebeen recorded in great abundance in nearshore settings due to salinity preferences (Davey 1970; Downie et al. 1971; Li and Habib 1996).

3.1.2. Estuarine group Ceratioid and gymnodinioid dinoﬂagellate cysts are grouped because of their nearshore paleoenvironmen-

Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012 tal preference as discussed by May (1977), Wilpshaar and Leerveld (1994) and Leerveld (1995). According to these authors, ceratioid cysts indicate restricted marine or low-salinity environments suggesting nearshore, lagoonal or back-barrier environments. Based on morphological studies, May (1977) concluded that gymnodinioid dinoﬂagellate cysts are indicative of estuarine environments. He proposed that the unique accordion shape and wall canals of gymnodinioid species are highly eﬀective mechanisms that allow them to tolerate rapid changes in salinity.

Figure 2. Stratigraphic columns of the Aico and Buitrera 3.1.3. Terrestrial group Creek sections showing the main lithostratigraphic units from the Santonian–Maastrichtian succession in the Upper Pollen and spores dominate this group and Magdalena Valley basin. indicate terrestrial input. If the parent plant can be 116 S. Garzon et al.

Figure 3. Schematic model showing the distribution of palynological assemblages from onshore–oﬀshore and their relationship to an idealized sequence-stratigraphic section. Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012

identified, then we are able to make some inferences not require moist soil to reproduce and spread, so about the local paleoenvironment prevailing at the their occurrence in coastal settings is considered to time of deposition and the coastal and hinterland indicate transport via river input from neighboring vegetation. Consequently, we can also determine if dry lands. At times, reconstructing the vegetation hydrophilic or xerophilic conditions (whether or not can be difficult because many of the Late Cretaceous a plant can grow and reproduce in conditions with pollen and spore types have no known living high/low-water availability, respectively) existed. counterpart. Plants such as ferns that reproduce via spores are considered hydrophilic, as the spores require soil 4. Results with high-moisture content to produce gametophytes that will generate the next generation of plants. 4.1. Palynostratigraphy Their predominance in a section can reflect swamp The stratigraphic distributions of terrestrial, estuarine environments. Xerophylic pollen-producing plants do and marine palynomorphs for both sections are shown Palynology 117

Table 1. List of palynomorphs used to define the palyno- From oldest to youngest, Zone 1 is characterized logical groups for sequence-stratigraphic interpretation. by the co-occurrence of Araucariacites sp. and Marine Scabratriletes sp. Zone 2, the Odontochitina zone, is Peridinioid Gonyaulacoid characterized by the occurrence of Odontochitina Andalusiella gabonensis Areoligera spp. costata, O. operculata and O. porifera. Zone 3 is Andalusiella mauthei Circulodinium distinctum divided into two subzones: the Hamulatisporis zone Andalusiella polymorpha Coronifera sp. Andalusiella/ Cyclonephelium spp. defined by the occurrence of Hamulatisporis caperatus, Palaeocystodinium Diphyes sp. Muerrigerisporis ardilensis, Araucariacites australis and complex Exochosphaeridium sp. Neorastrickia densus; and the overlying Andalusiella Cerodinium spp. Exochosphaeridium bifidum Cerodinium diebelii Heterosphaeridium difficile zone characterized by the common occurrence of Isabelidinium sp. Hystrichodinium pulchrum Andalusiella mauthei and A. polymorpha. Finally, Palaeocystodinium spp. Oligosphaeridium complex Zone 4, the Cerodinium zone, is defined by the first Palaeohystrichophora Spiniferites spp. occurrence of Cerodinium diebelii, and the last occur- infusorioides Senegalinium spp. rences of A. australis. Buttinia andreevi, Foveotriletes Trithyrodinium fragile margaritae and Echimonocolpites protofranciscoi occur sparsely within this zone. The zonation helps correlate Nearshore/estuarine the two sections in the absence of stratigraphically Ceratioid Gymnodinioid Odontochitina costata Alisogymnium spp. significant marine microfossils (e.g. foraminifera, Odontochitina operculata Alisogymnium euclaense nannofossils). Odontochitina porifera Dinogymnium spp. Dinogymnium acuminatum Dinogymnium digitus 4.2. Distribution of key palynological assemblages Dinogymnium ‘‘lamarense’’ Dinogymnium undulosum Within the broad palynomorph groups, six distinctive Terrestrial assemblages were recognized: those dominated by Spores Pollen ceratioid dinoflagellate cysts, gonyaulacoid dinoflagel- Appendicisporites Araucariacites spp. ‘‘protoerdtmanii’’ Araucariacites australis late cysts, gymnodinioid dinoflagellate cysts, peridi- Cicatricosisporites sp. Bombacacidites ‘‘inciertus’’ nioid dinoflagellate cysts, spores and pollen. Cicatricosisporites Buttinia andreevi Changes in these assemblages are visible in the ‘‘bifurcates’’ Echimonocolpites protofranciscoi Distaverrusporites spp. Ephedripites sp. vertical distribution of species (Figures 4–7). The Echitriletes spp. Gnetaceaepollenites relative abundances of species in both sections (Figures Echitriletes intercolensis ‘‘pseudoboltenhagenii’’ 10 and 11) reveal some interesting trends. These Foveotriletes Psilatricolpites sp. vertical changes in palynological assemblages are ‘‘protomargaritae’’ Retistephanocolporites sp. Foveotriletes margaritae Arecipites spp. described below. Gabonisporis vigourouxii Monocolpopollenites spp. Hamulatisporis caperatus Monocolpopollenites Laevigatosporites spp. spheroidites 4.2.1. Aico Creek section Laevigatosporites tibuensis Psilamonocolpites sp. Muerrigerisporis sp. Psilamonocolpites medius Figure 10 illustrates the vertical distribution of the six Neoraistrickia sp. Proxapertites ‘‘foveoreticulatus’’ assemblages recovered at the Aico Creek section. Paly- Polypodiisporites sp. Proxapertites nomorph recovery varies from fair to abundant with Psilatriletes spp. minutihumbertoides

Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012 some barren intervals occurring throughout the section. Rotverrusporites spp. Proxapertites maracaiboensis Rugotriletes sp. Racemonocolpites sp. A spike in ceratioid cysts occurs in the lower Lidita Rugulatisporis Retimonocolpites sp. Formation at 43.5 m although numbers quickly ‘‘vermiculatus’’ Spinizonocolpites sutae decline. At 46.4 m, gonyaulacoid cysts dominate with Scabratriletes sp. minor abundances of spores and pollen. From 79 to Scabratriletes granularis Striatriletes spp. 89 m in the El Cobre Formation, gymnodinioid cysts Trilites ‘‘psilatus’’ dominate the assemblage with gonyaulacoid cysts, Verrucatotriletes spp. pollen and spores as minor components. The upper- Zlivisporis blanensis most El Cobre Formation (114.5–127 m) contains a predominantly marine assemblage dominated by gonyaulacoid cysts with decreasing gymnodinioid cyst in Figures 4–7. Based on the distribution of species abundances, and with ceratioid cysts and spores recovered, four stratigraphically distinct palynological common at 125 m. At the base of the Upper Lidita assemblage zones (1–4) are deﬁned at Aico Creek Formation (134 m), gonyaulacoid cysts are recorded (Figure 8). Only Zones 3 and 4 are identiﬁed at followed by the occurrence of gymnodinioid cysts, Buitrera Creek (Figure 9). spores and pollen at 143.5 m. The interval from 145 to 118 S. Garzon et al. Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012

Plate 1. Light photomicrographs of key species of marine and terrestrial palynomorphs present in the studied sections. Figure 1. Buttinia andreevi,BuitreraCreek609.8m,EFX36.Figure2.Echimonocolpites protofranciscoi,AicoCreek203m,EFS14.Figure3. Cerodinium diebelii, Aico Creek 229.9 m, EF O44. Figure 4. Foveotriletes margaritae, Aico Creek 229.9 m, S36/3. Figure 5. Spinizonocolpites sutae, Aico Creek 203 m, EF V27/3. Figure 6. Oligosphaeridium complex, Aico Creek 79 m, EF R27/2. Figure 7. Alisogymnium euclaense, Aico Creek 229.9 m, EF K9. Figure 8. Odontochitina operculata, Aico Creek 125 m, EF E18/4. Palynology 119 Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012

Plate 2. Light photomicrographs of species of marine and terrestrial palynomorphs present in the studied sections. Figure 1. Bacumorphomonocolpites tausae, Buitrera Creek 619.4 m, EF T42/1. Figure 2. Bombacacidites ‘‘inciertus’’, Aico Creek 207.7 m, EF P6/4. Figure 3. Gnetaceapollenites ‘‘pseudoboltehagenii’’, Aico Creek 205 m, EF P25/2. Figure 4. Dinogymnium undulosum, Aico Creek 89 m, EF M25. Figure 5. Alisogymnium ‘‘glotonicus’’, Aico Creek 221.4 m, W39. Figure 6. Psilamonocolpites medius, Aico Creek 221.4 m, EF P12/3. Figure 7. Hamulatisporis caperatus, Aico Creek 216.7 m, EF H12/3. Figure 8. Gabonisporis vigourouxii, Aico Creek 143.5 m, EF Q18/2. Figure 9. Proxapertites maracaiboensis, Buitrera Creek 609.8 m, EF V38/1. 120 S. Garzon et al.

Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012 Figure 4. Distribution chart of terrestrial palynomorphs from the Aico Creek section.

185 m is barren of palynomorphs. At the base of the The ﬁrst occurrence of the important Campanian– Buscavidas Formation (188.5–191.5 m), peridinioid Maastrichtian palynological markers, Echimonocol- and gonyaulacoid cysts dominate the assemblage. pites protofranciscoi and Buttinia andreevi (Muller Gymnodinioid cysts, spores and pollen increase in et al. 1987; Jaramillo and Rueda 2004), are at abundance at 200.7 m followed by a spike in spore 200.7 m and 202 m, respectively, in Zone 4 (see abundance at 203 m with minor pollen numbers. Figures 5 and 8). We place the Campanian–Maas- Terrestrial palynomorphs dominate the assemblage at trichtian boundary above the ﬁrst occurrence within 205.7 m with gymnodinioid and gonyaulacoid cysts as the Buscavidas Formation at 240 m in the Aico Creek minor components. From 207.7 to 229.5 m gonyaula- section (Figure 10). This choice of placement for the coid, gymnodinioid and peridinioid cyst abundances Campanian–Maastrichtian boundary is consistent with increase. Pollen and spores dominate the palynological our sequence-stratigraphic interpretation for the posi- assemblage at the top of the Buscavidas Formation tioning of the 71 Ma sequence boundary (Figure 10, from 275.7 to 276.7 m. see discussion in Section 5). Palynology 121 Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012

Figure 5. Distribution chart of marine palynomorphs from the Aico Creek section. 122 S. Garzon et al.

Figure 6. Distribution chart of terrestrial palynomorphs from the Buitrera Creek section.

4.2.2. Buitrera Creek section remain the dominant component up to the sample at

Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012 Figure 11 illustrates the vertical distribution of the six 359.5 m. Pollen and spores are minor components of assemblages recovered at the Buitrera Creek section. these predominantly marine assemblages. Recovery in Palynomorph recovery ranges from fair to abundant the upper part of the Buscavidas Formation is poor throughout, with the exception of barren intervals at with the exception of common spores at 409 m and the base and middle part of the upper Lidita abundant pollen at 609.8 m. In general, at the Buitrera Formation. Creek section, peridinioid cysts dominate the marine At 19.2 m, at the base of the section in the El Cobre assemblages; this is in contrast to their rare presence at Formation, the palynological assemblage is dominated the Aico Creek section where gonyaulacoid cysts by terrestrial palynomorphs associated with gymnodi- dominate the dinoﬂagellate assemblages. nioid cysts. Peaks of peridinioid cysts are observed at The ﬁrst observed occurrence of the Campanian– 28.8, 56 and 78.4 m and dominate the upper part of the Maastrichtian palynological markers, Echimonocol- El Cobre Formation. Near the top of the Upper Lidita pites protofranciscoi and Buttinia andreevi (Muller Formation (198.6 m) and base of the Buscavidas et al. 1987; Jaramillo and Rueda 2004), is in the Formation (219.6 m), only peridinioid cysts are uppermost part of the Buscavidas Formation at recorded. Gonyaulacoid and gymnodinioid cysts re- Buitrera Creek at the top of Zone 4 (i.e. the two appear in the section at 238.3 m but peridinioid cysts samples above 600 m on Figures 7 and 11). No Palynology 123

Figure 7. Distribution chart of marine palynomorphs from the Buitrera Creek section.

samples could be obtained between 469.8 m and data to assess the signiﬁcance of the observed patterns. 609.8 m where the section is not accessible. These DCA is an ordination method used to summarize data

Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012 species could therefore be present as low as 470 m, i.e. variation in a small number of dimensions. The above 469.8 m. On this basis, and on the basis of our ordination was performed on 5 of the 6 palynological sequence-stratigraphic interpretation (see Figure 11 assemblage (i.e. peridinioid cysts, gonyaulacoid cysts, and Section 5 for details), we placed the Campanian– gymnodinioid cysts, pollen and spores) percentage Maastrichtian boundary at 475 m. data from both of the studied stratigraphic sections; ceratioid cysts were not included due to their sparse occurrence at Aico Creek and their absence at Buitrera 5. Sequence-stratigraphic interpretation and discussion Creek. To analyze the distribution of palynomorph assem- Marine affinity palynomorphs (i.e. sum of peridi- blages within a sequence-stratigraphic framework, it is nioid and gonyaulacoid cyst percentages) were com- assumed that a regular pattern of upsection changes in pared with estuarine affinity palynomorphs (i.e. sum of palynological assemblages correspond to environmen- gymnodinioid cyst percentages) from Aico Creek and tal changes associated with sea-level rise and fall yielded a Spearman’s rank correlation coefficient of – (eustacy). Spearman correlation tests and Detrended 0.39, p-value 0.1075, which indicates a moderate Correspondence Analysis (DCA) (Hill and Gauch negative correlation between the two groups. Estuarine 1980) were performed on the palynomorph percentage affinity palynomorphs were then compared with Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012 124 .Garzon S. tal. et

Figure 8. Palynological range chart of the Aico Creek section. (Terrestrial taxa in black, marine taxa in gray.) Palynology 125

Figure 9. Palynological range chart of the Buitrera Creek section. (Terrestrial taxa in black, marine taxa in gray.)

terrestrial affinity palynomorphs (i.e. spores and (gonyaulacoid cysts and/or peridinioid cysts) and the pollen) from Aico Creek and a Spearman’s rank scarcity of terrestrial palynomorphs. A gradual de- correlation coefficient of –0.58, p-value 0.01341, was crease in open marine dinoflagellates, the occurrence of determined. Comparison between marine affinity estuarine dinoflagellates and a consistent presence of palynomorphs and terrestrial affinity palynomorphs terrestrial palynomorphs represent the onset of the from Aico Creek yielded a Spearman’s rank correla- Highstand Systems Tract (HST). tion coefficient of –0.56, p-value 0.009114, indicating In terms of sedimentary facies, limestone and chert moderate negative correlation. An onshore–offshore are considered to represent basinal paleoenvironments gradient is apparent on the DCA1 axis for the Aico whereas mudstone and sandstone are considered to Creek DCA biplot (Figure 12); pollen plots closely to represent more proximal paleoenvironments. Since

Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012 spores, followed by gymnodinioid cysts, and then these basinal and proximal paleoenvironments are gonyaulacoid cysts and peridinioid cysts. A similar lateral facies equivalents, the sequence-stratigraphic pattern for palynological assemblages ordered along a interpretation of lithologic data relied heavily on the gradient on the DCA1 axis is seen for the Buitrera observed patterns of upsection lithologic changes Creek DCA biplot (Figure 12). rather than lithology at any particular depth. The The upsection changes of the palynomorph assem- observed upsection lithology change (and/or asso- blages described above (Figures 10 and 11) were ciated palynomorph-assemblage change) therefore combined with a conventional lithological interpreta- depended upon the paleoenvironment existing at the tion to establish a sequence-stratigraphic framework. time prior to the onset of relative sea-level changes. In general, the Lowstand System Tract (LST) is characterized by abundance spikes of spores accompanied by pollen whereas the Transgressive Systems 5.1. Aico Creek section Tract (TST) is indicated by the occurrence of estuarine At the base of the section, up to 43.5 m, the poor dinoflagellates (ceratioid cysts and/or gymnodinioid recovery of palynomorphs prevented sequence-strati- cysts). Maximum Flooding Surfaces (MFS) are usually graphic interpretation as only a few specimens of represented by abundant open marine dinoflagellates estuarine dinoflagellates (i.e. gymnodinioid cysts), 126 S. Garzon et al. Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012

Figure 10. Stratigraphic distribution chart showing the relative abundance of the six palynological assemblages (percentage) at the Aico Creek section. Also shown are the lithostratigraphy and the sequence-stratigraphic interpretation correlated with the Haq et al. (1987) eustatic curve plotted against the Geologic Time Scale of Gradstein et al. (2004). Percentage values for each assemblage is calculated using the total number of specimens of each assemblage against the sum of specimens of all six palynological assemblages.

peridinioid cysts and spores were found in this part of correlation to the global cycle chart (Haq et al. the section. In this zone, system tracts are interpreted 1987). At 43.5 m a MFS is placed near the top of the on the basis of lithological changes as well as lower Lidita Formation based on the occurrence of a Palynology 127 Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012

Figure 11. Stratigraphic distribution chart showing the relative abundance of the six palynological groups (percentage) at the Buitrera Creek section. Also shown are the lithostratigraphy and the sequence-stratigraphic interpretation correlated with the Haq et al. (1987) eustatic curve plotted against the Geologic Time Scale of Gradstein et al. (2004). Percentage values for each assemblage is calculated using the total number of specimens of each assemblage against the sum of specimens of all six palynological assemblages. 128 S. Garzon et al. Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012

Figure 12. DCA biplots of palynological assemblage distribution at the Aico and Buitrera Creek sections. Palynology 129

spike in abundance of ceratioid cysts coincident with continued presence of spores and pollen represents an overall lithologic change from limestone in the basinward transport of palynomorphs from terrestrial underlying LST to chert/limestone in the TST, which settings. The inferred decrease of marine and estuarine suggests an overall deepening of water depth at the palynomorphs above 230 m and continued presence of site. Within the top of the overlying HST, i.e. from 79 terrestrial palynomorphs are interpreted to represent to 89 m, the dominance of gymnodinioid cysts coupled shoaling in the HST. The sequence boundary (at 71 with the occurrence of terrestrial palynomorphs is Ma) is placed at c. 232 m. The overlying sequence and interpreted to correspond to relative sea-level fall at the sequence boundary (at 68 Ma) is inferred primarily on end of the HST. Sandstone deposition at 99.7 m is the basis of the coarse sandstone beds above the 68 Ma interpreted to represent the onset of the Shelf Margin sequence boundary at 252 m, i.e. the base of the Systems Tract (SMST ¼ lowstand deposition), i.e. a sandstone beds. Lowstand deposition is interpreted sequence boundary (at 83 Ma) is placed below the from the entire interval above the sequence boundary sandstone. At 114.5 m, the occurrence of estuarine based on the abundances of terrestrial palynomorphs dinoflagellates coupled with high abundances of at 275.7 and 276.7 m. gonyaulacoid cysts is associated with the transgressive system tract (TST). A subsequent decrease of gonyaulacoid cysts, together with the occurrence of spores and 5.2. Buitrera Creek section estuarine dinoflagellates at 125 m, is interpreted to At the base of the Buitrera Creek section (9.6–28.8 m), represent the end of the HST, i.e. a sequence boundary the occurrence of gymnodinioid cysts along with (at 80 Ma). The sequence boundary is at the base of the spores and pollen are taken to represent the LST. An sandstone at 125 m. increase in peridinioid cysts at 56 m indicates the onset Starting at c. 125 m, the upsection vertical change of the TST and a spike of peridinioid cysts at 78.4 m at from sandstone to mudstone to limestone is interpreted the top of the TST is interpreted as the MFS. A as representing the progressive deepening from LST to sequence boundary (80 Ma) is placed at 81 m. In the TST within the overlying sequence. The subsequent sequence above the 80 Ma sequence boundary, the shift from chert to limestone at 135 m is taken to overlying lithologic change from mudstone to lime- represent slow relative sea-level fall during the late stone to chert is taken to represent an overall HST. The sequence boundary (at 79 Ma) is placed deepening associated with relative sea-level rise. above the finer-grained limestone and below the base A sequence boundary corresponding to relative of the overlying coarser-grained limestone. The over- sea-level fall at 79 Ma is inferred to be within the chert lying LST contains gymnodinioid cysts, pollen and sequence. This is consistent with the stratigraphic spores which represents the major sea-level fall framework interpreted from the Aico Creek section (associated with the 79 Ma sequence boundary). A (Figure 10) although the samples are barren and there sequence boundary (at 77.5 Ma) is placed at c. 155 m are no lithologic changes. The absence of lithologic at the base of the coarse limestone. change may simply mean that water depth remained Above the sequence boundary, the lithologic deep despite a relative sea-level fall. Indeed, the sea- change from limestone to chert is interpreted to level fall at 79 Ma was relatively minor. represent an overall relative sea-level rise during the A sequence boundary is placed at the base of the LST and TST. The shift from chert to limestone to limestone bed at c. 160 m which is interpreted to

Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012 mudstone is interpreted to represent progressive correspond to an abrupt relative sea-level fall at 77.5 shoaling during relative sea-level fall associated with Ma. The increase in peridinioid cysts at 198.6 m is the HST. Palynomorphs are absent from the LST, TST taken to represent the top of the TST, i.e. the MFS. and base of the HST; however, marine and estuarine The overlying lithologic change from chert to lime- palynomorphs co-occur in the top of the HST. Within stone to mudstone is taken to represent progressive the context of the sequence-stratigraphic interpreta- shoaling and relative sea-level fall in the HST. At the tion, the late HST represents the lowest water depth top of the HST estuarine and terrestrial palynomorphs paleoenvironments for this sequence at the Aico Creek become successively abundant, which likewise is section. The sequence boundary (at 75 Ma) is placed at consistent with upward shoaling. The sequence bound- the base of the coarse limestones. The basal-most LST ary (at 75 Ma) is placed at c. 260 m, just below the has an increase in spore and pollen, which is taken to decrease in marine palynomorphs at 262.2 m. In the represent the relative sea-level fall associated with the overlying LST, the upsection transition from mudstone 75 Ma sequence boundary. In the overlying part of the to limestone is taken to indicate relative sea-level rise. LST and overlying TST, the occurrence of gonyaula- The increased abundance of peridinioid cysts at coid and peridinioid cysts is interpreted to represent 294.9 m is taken to correspond to the top of the progressive relative sea-level rise. If correct, the TST. The increased abundance of pollen/spore at 130 S. Garzon et al.

302.9 m and concomitant decrease in peridinioid cysts is taken to indicate shoaling and relative sea- level fall in the HST. The 71 Ma sequence boundary is placed at c. 400 m based on the abrupt increase in spores and pollen at 409 m. The sandstone at c. 465 m is considered to be within the LST. The continued presence of terrestrial and estuarine palynomorphs together with the absence of peridinioid cysts from the overlying TST and HST is taken to indicate progressive shoaling. The 68 Ma sequence boundary is placed at the base of the sandstone at c. 490 m. Based on (1) the absence of Echimonocolpites protofranciscoi and Buttinia andreevi up to the sample at 469.8 m; (2) their presence at 609.8 m; and (3) the sequence-stratigraphic interpretation which places the 71 Ma sequence boundary at 400 m and the 68 Ma sequence boundary at 490 m, we place the Campa- nian–Maastrichtian boundary at 475 m (Figure 11). This interpretation also minimizes the diﬀerence in thickness of the Buscavidas Formation between the Aico and Buitrera Creek sections. The section just below the unsampled portion of the Buscavidas Formation is placed within the overlying LST. The sandstone above the inaccessible portion of the Buscavidas Formation is placed within the LST of the overlying sequence. In other words, the 63 Ma sequence boundary is placed at c. 600 m.

6. Age and correlation Age dating the Coniacian–Santonian and Santonian– Campanian boundaries at the Aico Creek section was accomplished using ammonite and inoceramid data from previous studies (Etayo-Serna 1994; Villamil et al. 1998) as well as some key palynological markers observed in this study and our sequence-stratigraphic interpretation. On these bases, the Santonian–Campa- nian boundary is identiﬁed at 89 m in Aico Creek

Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012 within the middle part of the El Cobre Formation. The Santonian–Campanian boundary is below the section at Buitrera Creek. For the Campanian–Maastrichtian boundary, palynologic markers such as Foveotriletes margaritae, Figure 13. Graphic comparison showing correlation Buttinia andreevi and Echimonocolpites protofranciscoi between the Aico Creek and Buitrera Creek sections using (Muller et al. 1987; Jaramillo and Rueda 2004) were palynological zones, first and last appearance datum, identified in both sections and a framework zonation maximum flooding surface and sequence boundary as stratigraphic markers. The table provides the depths of key (Zones 1–4) was established. Poor and erratic recovery stratigraphic events used for the graphic comparison. The in some parts of both sections and covered intervals numbers in red are inferred elevations for the top of Zone 1 presented a challenge to age assignment based solely and Zone 2 at the Buitrera Creek section based on this on palynology. The Campanian–Maastrichtian bound- comparison. ary is picked at 240 m in the Aico Creek section within the Buscavidas Formation. At the Buitrera Creek both outcrop sections, the boundary is between the section, the Campanian–Maastrichtian boundary is sequence boundaries assigned to sea-level falls at 71 placed at 475 m within the Buscavidas Formation. In and 68 Ma. Palynology 131

Correlation between Aico and Buitrera Creek was support during her masters thesis research project. achieved using the palynostratigraphic Zones 1–4 and The authors also thank Dr Carlos Jaramillo, Carlos Santos and Manuel Paez for their collaboration with this the sequence-stratigraphic approach described in the project. previous section. Figure 13 presents the correlation of the two sections based on the biozones and sequence boundaries. Author biographies SANDRA GARZON is from Bucaramanga, 7. Conclusions Colombia. She obtained her bachelor’s degree Palynological data recovered from the Aico and in geology from the Universidad Industrial the Santander in 2007. Sandra worked at the Buitrera Creek sections in the UMV has provided Colombian oil company ECOPETROL for useful biostratigraphic and paleoenvironmental infor- two years as a junior biostratigrapher before mation. Four palynological zones are defined that help coming to the United States in the summer of to differentiate the lithologically monotonous Lower 2009 to obtain her Master of Science degree from the Lidita, El Cobre, Upper Lidita and Buscavidas Department of Geology and Geophysics at Louisiana State formations. University. Once at Louisiana State University she worked as educational curatorial assistant for the LSU Museum of Cyclic patterns in palynomorph abundances and Natural Science. Sandra worked as an intern with BP in the lithological changes were used to construct a summer of 2011 and joined BP full-time in February 2012 sequence-stratigraphic framework. In both sections, based in Houston, Texas. the absolute abundances of the various palynomorph assemblages enabled recognition of lowstand systems SOPHIE WARNY is an Assistant Professor tracts, transgressive systems tracts, maximum flood- of Palynology in the department of Geology ing surfaces (MFSs) and highstand systems tracts. and Geophysics & at the Museum of Natural Science at Louisiana State University in The sequence-stratigraphic interpretation was based Baton Rouge. She has a long history with on calibration to the Haq et al. (1987) eustatic sea- AASP as she won the AASP Student Award level curve for the Santonian–Early Maastrichtian in 1996. She received her Ph.D. from the interval. Additionally, previous conventional se- UniversiteĆatholique de Louvain, in Belgium working with quence-stratigraphic interpretations for the same Dr Jean-Pierre Suc. Her doctoral dissertation focused on the lithostratigraphic units in other parts of the UMV Messinian Salinity Crisis. Since graduating, she has been working on Antarctic sediments that were acquired via the basin (e.g. Guerrero 2002) have been incorporated ANDRILL SMS and the SHALDRIL programs. In 2011, within our study. she received the prestigious NSF CAREER award to support The results of this study support earlier observa- her palynological research in Antarctica. Now that she lives tions by Poumot (1989), Gregory and Hart (1992) in Louisiana, her research focus has expanded to the Gulf of and Holz and Dias (1998) who proposed that Mexico region and to some other sequences thanks to her students’ research interests. In addition to her research, she palynological data is a valuable tool for sequence- teaches Historical Geology, Paleobotany, and Micropaleon- stratigraphic interpretation. In diverse geological tology. She also manages the education and outreach settings such as the structurally complex UMV, programs for the Museum. She currently has a research where conventional sequence-stratigraphic tools (i.e. group at the remodeled CENEX facility at LSU (Baton seismic, stacking patterns, lithological changes Rouge, Louisiana) that is composed of four master’s students and three Ph.D. students.

Downloaded by [T&F Internal Users], [Jayne Kay] at 01:32 07 June 2012 alone or calcareous microfossil content) cannot be applied, palynological data is essential. Future work PHILIP BART is an Associate Professor in on additional outcrop sections is needed to sub- the Department of Geology and Geophysics at stantiate and build on the framework presented in Louisiana State University in Baton Rouge. He earned his Ph.D. degree from Rice this paper. University in Houston, working with Dr John Anderson. He received the Presidential Early Career Award for Scientists and En- gineers (PECASE) in 2001 for his seismic and sequence Acknowledgements stratigraphic research in Antarctica. His other research interests The authors are grateful to Dr David Pocknall and consists in evaluating the sequence stratigraphy of the last two anonymous reviewers for their in-depth critique of glacial cycle and the sea-level elevation at the peak of the LGM the manuscript, which resulted in a much-improved based on seismic data from the northeastern Gulf of Mexico. paper. S. Garzon would like to thank the Museum of Natural Science and the Department of Geology and Geophysics CENEX Laboratory at Louisiana State References University (Baton Rouge, LA), the Smithsonian Tropical Brown C. 2008. In: Riding J, Warny S, editors. Palynological Research Institute in Panama and the Colombian techniques. Dallas (TX): American Association of Petroleum Institute for their ﬁnancial and logistical Stratigraphic Palynologists Foundation. 137 p. 132 S. Garzon et al.

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