Important Paleotectonic and ChronostratigraphicConsiderations of the Late Paleocene in the Northernmost

Andes as Constrained by Paleocene Rocks in the Cerrejón CoalMine, Guajira, Colombia

G. BAYONA (1), C. JARAMILLO (2), M. RUEDA (1), A. PARDO (3), A. CHRISTIE (4) &HERNANDEZ, G. (4)

(1) Corporación Geológica ARES, Bogotá, Colombia(2) Instituto Colombiano del Petróleo, Piedecuesta, Colombia

(3) Universidad de Caldas, Manizales, Colombia(4) Carbones del Cerrejón. Cerrejón, Colombia

ABSTRACT

Paleocene rocks east of the Central Cordilleraand Sierra Nevada de Santa Marta (SNSM) contain thickhydrocarbon reservoir units and coal beds. However, thelateral distribution of these beds is poorly understood.This work links biozones, patterns of deposition andpetrofacies in Paleocene Manantial, Cerrejón andPalmito formations in order to improve thechronostratigraphic and tectonic framework ofPaleocene basins in the northernmost Andes.

Lithofacies, sedimentary structures andpalynological associations in the aprox. 1.3-km-thickPaleocene succession in the Cerrejón coal minesuggest that a mixed platform was covered and buriedby coal-bearing siliciclastic strata, which accumulated intidal-flat plains and later in littoral coastal plains.Palynological analysis of 200 samples collected in theCerrejón Formation defines 13 biozones, which arecharacterized by unique assemblages of pollen, sporesand dinoflagellate cysts. These biozones are within theFoveotricolpites perforatus zone (Late Paleocene).Although the stacking pattern of deposition is dominantlyaggradational, at least nine major surfaces ofstratigraphic correlation (e.g., maximum floodingsurfaces) may be traceable basinwide using our detailedchronostratigraphic framework. Argillaceous sandstonesin the Cerrejón and Palmito formations include well-preserved feldspar, feldspar-quartz aggregates,metamorphic lithic and fine-grained sedimentary lithicgrains. This assemblage suggests that first-cyclesandstones were supplied from basement-involvedblocks and buried rapidly.

Drowning of the platform, influx of basement-derived grains and rapid subsidence of the basin may bea response of initial uplift of the SNSM during the LatePaleocene. This pulse likely controlled vertical andlateral distribution of coal-bearing strata, which isconsidered an important source of methane for theRancheria-Cesar basin, in a newly formed flexural-subsiding basin.

RESUMEN

Al este de la Cordillera Central de Colombia ySierra Nevada de Santa Marta (SNSM) se encuentranimportantes unidades reservorio y mantos de carbón deinterés económico, pero con un pobre conocimiento desu distribución lateral. Este trabajo integra informaciónde biozonas palinológicas, patrones de acumulación ypetrofacies de las unidades Paleocenas Manantial,Cerrejón y Palmito para mejorar el armazóncronoestratigráfico y tectonoestratigráfico de la cuencaPaleocena de los Andes más septentrionales.

La sucesión del Paleoceno expuesta en prediosde la mina del Cerrejón tiene un espesor aproximado de1.3 km, y la asociación de litofacies, estructurassedimentarias y palinomorfos sugieren la progradaciónde depósitos siliciclásticos con mantos de carbon,interpretados como depósitos de llanuras de mareas ycosteras, sobre carbonatos de plataforma somera. Laasociación de polen, esporas y dinoflagelados,identificados en el análisis de 200 muestraspalinológicas, definen 13 biozonas. Estas biozonasestán dentro de la zona Foveotricolpites perforatus delPaleoceno Tardio. Esta biozonación detallada permiteasignar una edad relativa a nueve superfices decorrelación estratigráfica, las cuales fueron identificadasa pesar del patrón agradacional de acumulación. Labuena preservación de feldespatos, agregados decuarzo-feldespatos, y fragmentos líticos metamórficos ysedimentarios en arenas con abundante matriz,sugieren un aporte de áreas fuente donde bloques debasamento estaban ya expuestos. Además, elenterramiento de estos depósitos fue rápido.

El levantamiento de la SNSM durante elPaleoceno Tardio se puede asociar al rápidohundimento de la plataforma y el relleno por detritosderivados de la Sierra. Este evento de deformacióngeneró una cuenca donde la subsidencia flexuralprobablemente controló la distribución lateral y verticalde matos de carbón, los cuales son potenciales fuentede gas metano en la cuenca Cesar-Rancheria.

G. BAYONA , C. JARAMILLO , M. RUEDA , A. PARDO , A. CHRISTIE & HERNANDEZ, G.

INTRODUCTION

Stratigraphic correlation of poorly datedsynorogenic continental beds has been a subjectof controversy. This is the case of Paleogenestrata east of the Central Cordillera of Colombiaand Sierra Nevada de Santa Marta (SNSM), whichaccumulated in tidally-influenced marginal andcontinental settings. In this paper, we presentsedimentologic, petrographic and palynologicaldata from the Manantial, coal-bearing Cerrejón,and Palmito Formations. Results from this studyallow (1) to identify patterns of deposition related topulses of deformation, (2) to define surfaces ofstratigraphic correlation that may be traceable bothin local and regional settings, and (3) todifferentiate coal beds for exploration purposes.The most significant contribution is that coal seamsand identified stratigraphic surfaces of correlationare characterized by a specific palynologicalbiozone.

REGIONAL SETTING

The Cerrejón coal mine is located in theRancheria River Valley and is bounded to the northby the Oca Fault, to the west by the easternfoothills of the SNSM, and to the east bynorthwest-verging thrust faults of the Perijá Range(Figure 1). Beds exposed in the study area have aregional southeastward dip and are locally foldedand affected by faults (Carbones de Cerrejón,2003a). Northwest-verging, basement-involveduplift of the SNSM and Perijá Range has beenconsidered of Pliocene – Pleistocene in age (seefigure 6 of Kellogg and Bonini, 1982). However,paleogeographic maps of Villamil (1999) show theSNSM as the northernmost elevation of theancestral Central Cordillera since the latestMaastrichtian – Early Paleocene time (Villamil,1999) with depositional systems migratingeastward to the Maracaibo lake (Van Andel, 1958;Vil lamil, 1999). The SNSM includesunmetamorphosed and metamorphic rocks rangingin age from Precambrian to Jurassic (Tschanz etal., 1974), and shows a structural relief of 12 km(Kellogg and Bonini, 1982). In contrast, the Perijárange exposes sedimentary and low-grademetamorphic rocks of Paleozoic age, as well asvolcanic and sedimentary rocks of Mesozoic age(Ujueta and Llinás, 1990).

Paleogene units exposed in the Cerrejóncoal mine are strategic for understanding thetiming of uplift of adjacent mountain belts (Figure2). The Cerrejón Formation rests conformably andin a gradational contact with the 170-to-440m thickManantial Formation (Haught et al., 1944). The

75m-thick Tabaco and 300m-thick PalmitoFormations overlie in a disconformity contact theCerrejón Formation (Ramos, 1990). The Manantialand Cerrejón Formations have been dated asPaleocene using mollusks (Etayo-Serna, 1979)and pollen (Van der Kaars, 1983). Tabaco andPalmito Formations are considered Eocene bytheir stratigraphic position (Ramos, 1990). Thestratigraphic nomenclature used in this paper foridentification of coal seams is the nomenclatureused by Carbones del Cerrejón (2003b).

METHODS

A composite stratigraphic section was builtusing cores (Figure 3) and unpublishedstratigraphic sections. The lower Palmito and thetop of the Cerrejón Formations were described inwell ERV-17954 (1158732 E, 1720056 N). Most ofthe Cerrejón Formation was described in wellsWRV-04752 (between coal seams 103-155;1152618 E, 1714524 N) and WRV-04774 (coalseams 45-110; 1151689 E, 1715562 N). Thelower part of the Cerrejón Formation (coal beds 30to 40) and the contact with the underlyingManantial Formation were described in wells PAT-11238 (1150686 E, 1716168 N) and SIS-07(1148579 E, 1711692 N), respectively. Partialstratigraphic columns between coal seams 40 to85 and in the Manantial Formation were surveyedin order to have a control of lateral distribution oflitofacies.

Two hundred samples were processed forpalynological analysis in wells WRV-04752 andWRV-04774, taking one sample each 3.5 m. Thepalynologic samples were prepared by thestandard procedure of digesting the sediments inHCl and HF and then oxidizing the sample ifnecessary (Traverse, 1988). The fuming HNO3technique was used to prepare the coals. Lightmicroscopy was used for routine palynologicalanalyses, and at least 200 palynomorphs persample were counted when possible. Majortaxonomic nomenclatural changes follow those inJaramillo and Dilcher (2000, 2001), Jaramillo(2002), and Pardo et al. (2003). Informal specieswere written between quotation marks, and taxauseful for biostratigraphy are illustrated in Plates 1-3. Palynological analysis of samples collected inthe other three wells are in progress.

Thirteen thin sections of fine-to-mediumgrained sandstones collected from the upperManantial, Cerrejón and lower Palmito Formationswere analyzed for identification of framework graintypes. Thin sections were stained for identificationof feldspars. Although calculation of modal graintypes is qualitative, the preliminary results permit

G. BAYONA , C. JARAMILLO , M. RUEDA , A. PARDO , A. CHRISTIE & HERNANDEZ, G.

the identification of important differences in grain-type population among these three units. Point-counting of these samples and additional study ofmore thin sections are in progress.

BIOSTRATIGRAPHY

The palynological assemblages studied atcores WRV-04752 and WRV-04774 (Figures 2 and3) correspond to the Foveotricolpites perforatuszone defined by Germeraad et al. (1968) and thezone Cu-02 of Jaramillo et al (in press).Foveotricolpites perforatus and Bombacaciditesannae occur in the entire studied interval. Thiszone is presently dated as Late Paleocene (Mulleret al., 1987).

Thirteen palynological local zones areproposed with an average of 48 stratigraphicmeters per zone. Sixteen coal seams werecharacterized by unique assemblages that couldalso be used for stratigraphic correlation incombination with the proposed palynologicalzones. Eight additional coal seams were sterile forpalynology and could not be characterized. Majorstructural repetitions were not found. Informalspecies were written between quotation marks,and taxa useful for biostratigraphy are illustrated inPlates 1-3. The zones are based mainly on acmeintervals and a few first and last taxa occurrences.

Zone Ce-01, Proxapertites psilatus – RetidiporitesmagdalenensisInterval: 357.59 m – 328.60 m, Core WRV04774Top: offset of acme of P. psilatus and R. magdalenensisBase: onset of acme of Proxapertites psilatusAssemblage: Good recovery of palynomorphs, with highfrequencies of Proxapertites psilatus, Proxapertitesoperculatus and Psilamonocolpites medius. Somedinocysts were also recovered within this zone, whichincludes the coal seam 45.Zone Ce-02, Psilastephanocolpites globulus – Tetradites“psilatus”Interval: 326.82 m – 235.32 m, Core WRV04774.Top: offset of local acme of P. globulus and T. “psilatus”Base: offset of local acme of Proxapertites psilatus andRetidiporites magdalenensisAssemblage: High frequencies of Camarozonosporitessp., G e m m a s t e p h a n o c o l p i t e s g e m m a t u s ,Psilastephanocolpites globulus, Mauritiidites franciscoivar. pachyexinatus and Tetradites “psilatus” characterizethis zone, which includes the coal seams 50, 57, 60, 65,71 and 75.Zone Ce-03, Verrutriletes “viruelensis”Interval: 231.16 m – 118.25 m, Core WRV04774.Top: first local stratigraphic occurrence of IschyosporitesproblematicusBase: offset of local acme of P. globulus and T .“psilatus”.Assemblage: Poor to good recovery of palynomorphs,with moderate frequencies of Brevitricolporites sp.,

Mauritiidites franciscoi var. pachyexinatus, Proxapertitescursus, Si l tar ia sp. 4 (Jaramillo & Dilcher),Echistephanoporites “lafontanus”, Ephedripitesvanegensis and Laevigatosporites tibuensis. The firstlocal stratigraphic record of Verrutriletes “viruelensis”occurs at 216.90 m. Proxapertites operculatus isespecially abundant toward the top of this zone, whichincludes the coal seams 83, 95 and 100.Zone Ce-04, Ischyosporites problematicusInterval: 116.82 m – 100.60 m, Core WRV04774.Top: onset of local acme of PsilabrevitricolporitessimpliformisBase: first local stratigraphic occurrence ofIschyosporites problematicusAssemblage: Moderate frequencies of Psilatriletes 25 –50 um gr. and Psilamonocolpites medius together withthe first stratigraphic occurrence of I. problematicuscharacterize this zone, which includes the coal seams101 and 102.Zone Ce-05, Psilabrevitricolporites simpliformisInterval: 367.44 m – 338.65 m, Core WRV04752; 96.5 m– 66.15 m, Core WRV04774Top: offset of acme of Psilabrevitricolporites simpliformisBase: onset of acme of Psi labrev i t r ico lpor i tessimpliformisAssemblage: Characterized by moderate frequencies ofPsilabrevitricolporites simpliformis. Additional interestingfrequencies correspond to Ischyosporites problematicusand Diporopollis assamica, together with alternation ofhigh frequencies of Proxapertites cursus, Proxapertitesoperculatus and Psilatriletes (25-50um) group. Thiszone includes the coal seam 103.Zone Ce-06, Psilatriletes > 50 micronsInterval: 336.47 m – 318.56 m, Core WRV04752; 59 m –23.62 m, Core WRV04774Top: offset of acme of Psilatriletes > 50 microns, withinthe base of coal seam 110.Base: offset of local acme of PsilabrevitricolporitessimpliformisAssemblage: The highest frequency of Psilatriletes > 50microns at 318.56 m, within the base of coal seam #110, marks the top of this zone, which although presenta low recovery of palynomorphs includes the highestfrequency of Psilastephanocolpites globulus at 334.44 min the coal seam 105 and the highest frequency ofSyncolporites lisamae at 324.42 m.Zone Ce-07, Psilatriporites (Triatriopollenites type)Interval: 316.68m – 300.08m, Core WRV04752Top: offset of acme of Psilatriporites (Triatriopollenitestype)Base: offset of acme of Psilatriletes > 50 microns, withinthe base of coal seam 110Assemblage: Moderate frequencies of this sporomorphcharacterize this zone that includes the coal seam # 110and also presents moderates frequencies ofPsilamonocolpites medius, Proxapertites operculatusand Mauritiidites franciscoi, the first occurrence ofHorniella sp. 3 occurs here.Zone Ce-08, Mauritiidites franciscoi var. pachyexinatusInterval: 295.61 m – 258.88 m, Core WRV04752Top: offset of acme of Mauritiidites franciscoi var.pachyexinatus within coal seam 115Base: offset of acme of Psilatriporites (Triatriopollenitestype)

G. BAYONA , C. JARAMILLO , M. RUEDA , A. PARDO , A. CHRISTIE & HERNANDEZ, G.

Assemblage: Alternation of high frequencies of fernspores (Psilatriletes 20-25um gr., Ischyosporitesproblematicus, Laevigatosporites tibuensis) andProxapertites group, Psilamonocolpites medius andMauritiidites franciscoi were recognized within this zonethat also includes the last stratigraphic record ofE c h i s t e p h a n o p o r i t e s “ l a f o n t a n u s ” andMonocolpopollenites ovatus. Additionally presents theoccurrence of some dinoflagellates in the lower part.The coal seam # 114 is also included within this zone.Zone Ce-09, Ctenolophonidites lisamaeInterval: 252.66 m – 191.04 m, Core WRV04752Top: offset of acme of Ctenolophonidites lisamaeBase: offset of acme of Mauritiidites franciscoi var.pachyexinatus within coal seam # 115Assemblage: Poor to fair recovery of palynomorphscharacterize this zone. The top is defined based on thehighest frequency of Ctenolophonidites lisamae. Thehighest frequency of Scabratriporites “triangularis”occurs at 197.08 m and some dinocysts were recoveredfrom the lower part of this zone that also includes thecoal seams 120 and 125.Zone Ce-10, DinoflagellatesInterval: 187.22 m – 155.06 m, Core WRV04752Top: offset of acme of marine indicators (dinoflagellates,foraminifera lining, and Leiosphaeridia)Base: offset of acme of Ctenolophonidites lisamaeAssemblage: An acme of dinoflagellates, suggestingmarine influence, dominates this zone. Importantfrequencies of Proxaper t i tes opercu la tus ,Psilamonocolpites medius, plus Proxapertites cursus,and Mauritiidites franciscoi in lower proportions, as wellas moderate recovery of Retimonocolpites regiocharacterize this zone. The coal seam 130 is includedwithin this zone.Zone Ce-11, Momipites aff. africanusInterval: 151.1 m - 108.69 m, Core WRV04752Top: offset of acme of Momipites aff. africanusBase: offset of acme of marine indicatorsAssemblage: A moderate frequency of sporomorphMomipites aff. africanus characterize this zone, whichalso presents a moderate recovery of Laevigatosporitestibuensis and alternation of assemblages dominated byfern spores and by Proxapertites operculatus,Psilamonocolpites medius without Proxapertites cursus.High frequencies of Pediast rum sp. andPsilamonocolpites grandis were identified at 132.43 mand 111 m respectively. Some cysts of Dinogymniumsp., interpreted as reworked palynomorphs wererecovered from this zone. This zone also records thelast stratigraphic local occurrence of Bombacaciditesannae.Zone Ce-12, Striatricolporites digitatusInterval: 106.8 m – 51.3 m, Core WRV04752Top: Last stratigraphic occurrence of StriatricolporitesdigitatusBase: offset of acme of Momipites aff. africanusAssemblage: Characterized by high frequencies of fungispores and Proxapertites operculatus, Psilamonocolpitesmedius, Proxapertites cursus. Moderate frequencies ofCtenolophonidites lisamae and Psilastephanocolpitesglobulus were also recognized at the top of the zone,within the coal seam 155. Just below this seam theassemblages are dominated by fungi and Proxapertiteso p e r c u l a t u s , plus lower abundances of

Psilamonocolpites medius, Proxapertites cursus andsome dinoflagellate cysts. The coal seams 145 and 150are also included within this zone. Coal seam 145 isfully dominated by Proxapertites operculatus and fungi.Retitriletes “cristatus”, Proxapertites humbertoides andSyncolporites lisamae have here the last stratigraphicoccurrence.Zone Ce-13 of Ephedripi tes vanegensis –Curvimonocolpites inornatusInterval: 49.34 m– 19.66 m, Core WRV04752Top: offset of acme of Ephedr ip i tes a n dCurvimonocolpitesBase: Last stratigraphic occurrence of Striatricolporitesdigitatus

Assemblage: The uppermost zone ischaracterized by moderate frequencies of E. vanegensis– Curvimonocolpites, together with high frequencies offungi spores, Proxapertites operculatus a n dProxapertites cursus. Moderate recovery ofPsilamonocolpites medius, Psilatriletes gr. andDiporipollis assamica also characterize this zone. Thehighest frequency of Chomotriletes minor was identifiedat 19.66 m. (first sample analyzed).

STRATIGRAPHIC FRAMEWORK

Strata of the upper Manantial, Cerrejón andlower Palmito units show an upward decrease ofcalcareous beds and increasing influx ofterrigenous in the Manantial Formation,concentration of thick coal seams in the CerrejónFormation, and a general upward-coarsening trendin grain size of sandstones beds between theCerrejón and Palmito Formations (Figure 3).

Thin to medium-bedded strata in the upperManantial include fossiliferous packstones andwackestones interbedded with calcareoussandstones and mudstones. Internal sedimentarystructures are dominantly lenticular, wavy andripple laminated, and moderate bioturbation insome levels. Cross-bedding structures wereidentified in sandstones toward the top. Mollusksfragments are broken and concentrated in thick tomedium beds. These deposits accumulated in amixed shallow platform to fine-grained subtidalenvironments (lagoons), crossed by subtidalchannels to the top.

The Cerrejón Formation is aprox. 1000mthick (Ramos, 1990) and consists dominantly ofargillaceous sandstones, dark-colored siltstones,black shales and coal seams. A hypothetical typesuccession that consists of three segments isdefined for this unit. The lower segment consistseither of fossiliferous black shales and laminatedblack mudstones with thin lenticular laminaes ofsandstones (anoxic lagoonal, flooded coastal-plains environments) and/or flaser-laminatedsandstones (subtidal) (Figure 4). These bedsoverlie or underlie thick coal seams. The middlesegment of the type succession includes poorly

G. BAYONA , C. JARAMILLO , M. RUEDA , A. PARDO , A. CHRISTIE & HERNANDEZ, G.

bioturbated mudstones and sandstones with flaserand heterolithic lamination and disperse plantremains (subtidal and tidal flats). Both coarsening-and fining-upward trends of grain size arecommon. Coal seams have variable thickness inthis part of the succession. The upper segment ofthis type succession is dominated by fine-grained,massive to lenticularly-laminated, bioturbatedmudstones and siltstones with abundant plantremains, which are cut by thick to very thickmassive to cross-bedded sandstones (coastalplains crossed by channels). Medium to thin coalseams are common in the upper segment.

The base of the Palmito Formation includesfining-upward successions from conglomeraticcoarse-grained sandstones to massive light-colored mudstones and siltstones. These depositsare interpreted as the infilling of channel structurescutting coastal plains. The Tabaco Formation wasnot identified in the studied cores.

The conformable stratigraphic successiondescribed above shows the onset of siliciclasticdeposition on a former carbonate platform, and thegeneral progradation of continental settings overshallow-marine and tidal-dominated environments.However, nine events of flooding and/ordeepening-trend of depositional environmentscause an abrupt increase in the ratio ofaccommodation space/sediment supply, and theyare indicated as stratigraphic surfaces ofcorrelation. Coal seams are thicker near to thesestratigraphic surfaces, and they become thinner asthe ratio of accommodation space/sediment supplydecreases.

SANDSTONE COMPOSITION

Sandstones of the Cerrejón Formation aretexturally and compositionally immature.Framework grains include monocrystalline quartz,foliated polycrystalline quartz, plagioclase,potassium feldspars, microcline, sedimentary rockfragments (siltstones, chert), low-grademetamorphic rock fragments (graphitic and quartz-mica phyllite and schist), and quartz-feldsparaggregates (plutonic origin?) (Figure 5). Volcanicrock fragments were identified mainly toward thetop and in sandstones of the Palmito Formation.Cerrejón sandstones are friable and have a highcontent of argillaceous matrix (Figure 5).Calcareous cement is common in upper Manantialand lower Cerrejón sandstones. Glauconite wasidentified in medium, tabular bedded sandstonesabove coal seam 40 (Figure 5).

Sandstone composition becomes moreimmature upsection, changing from quartzarenitesto feldspathic litharenites. Composition of upper

Manantial – lower Cerrejón sandstones (below coalseam 40) varies from quartzarenites tosubquarzose calcareous sandstones (Qm75-90F3-

10Lt7-20 – 5 samples). Sandstone compositionbetween coal beds 40 to 50 is more mixed varyingfrom subquartzose to feldspathic litharenites(Qm30-80F10-30Lt10-44 – 4 samples). Sandstones ofthe upper Cerrejón and lower Palmito show anincreasing content of feldspars (Qm30-45F20-30Lt35-47

– 4 samples).

DISCUSSION AND CONLUSIONS

Detailed palynological analysis in theCerrejón Formation permits the characterization of13 biozones and 16 coal seams by uniqueassemblages of pollen, spores and dinoflagellatecysts. The palynological biozonation presented inthis paper also permits the assignation of a relativeage to nine stratigraphic surfaces that characterizeflooding and/or trend of deepening of depositionalenvironments. Therefore, coal seams andstratigraphic surfaces may be used for correlationof Paleocene strata in local and regional settings.

The dominant pattern of deposition withinthe 1-km-thick Upper Paleocene CerrejónFormation is aggradational to sl ightlyprogradational, as documented by: (1) the gradualchange in depositional settings from a mixedshallow-marine platform in the upper ManantialFormation to tidal and coastal plains in theCerrejón and Palmito Formations; (2) theprogradation and coarsening-upward trend ofstrata between stratigraphic surfaces of correlation,(3) gradual increase of grain size between upperCerrejón and lower Palmito sandstones as result ofprogradation of depositional systems.

Thickness of coal beds are primarilycontrolled by the ratio of accommodationspace/sediment supply. Thick coal bedscommonly underlie black shales, suggestingepisodes of flooding of coastal plains. In contrast,coal seams inerbedded with channel-fillsandstones toward the top are thinner than thoseoverlying black shales. Predictive models of coalgeometry and thickness (e.g., Holz et al., 2002)suggests that coal seams at the top of thesuccession may have a shorter lateral extent thanthose at the base of the succession.

The upsection enrichment of feldsparsgrains, and lithic grains of metamorphic andplutonic origin in sandstones of the Cerrejón andPalmito Formations suggests unroofing ofbasement-involved blocks with a thin sedimentarycover. The excellent preservation of feldspar andunstable fine-grained rock fragments indicates thatsource area(s) were located nearby. Excellent

G. BAYONA , C. JARAMILLO , M. RUEDA , A. PARDO , A. CHRISTIE & HERNANDEZ, G.

preservation of chemically unstable grainssuggests that burial processes in the basin wererapid enough to hide sediments from weatheringprocesses.

The >1.3 km-thick Upper Paleocenesuccession, the aggradational pattern of depositionand the composition of sandstones supports theinterpretation of synorogenic deposition asresponse of initial uplift of the SNSM during theLate Paleocene. However, more regional studiesare needed to determine whether the rapid filling ofthe basin corresponds to a foreland adjacent toeast-vergent uplift of the SNSM and CentralCordillera (e.g., Villamil, 1999), or a piggybackbasin between northwest-verging structures of theSNSM and Perijá range (e.g., Kellog and Bonini,1982).

Pulses of deformation likely controlledvertical and lateral distribution of (1) synorogeniccarbonate deposition of the Manantial Formation(examples of foreland carbonates are in Dorobek,1995), (2) drowning of the carbonate platform byarrival of synorogenic terrigenous detritus, (3) coalseams, and (4) migration of channels andprogradation of coarse-grained strata. Theunderstanding of the distribution of coal seams in anewly formed flexural-subsiding basin has aremarkable importance in the exploration ofmethane gas for the Rancheria-Cesar basin.

ACKNOWLEDGEMENTSCamilo Montes for introduction of the geology of theCerrejón coal mine, staff of the Cerrejón coal mine forlogistics and exceptional support during fieldwork, MartinCortés for revision of the manuscript, Jairo Roncanciofor designing some of the figures, Felipe de la Parra,Fabiany Herrera, Edwin Cadena, Paola Florez andHernan Antolinez for help during fieldwork. Carbonesde Cerrejón and Corporación Geológica ARESfinancially funded this study.

REFERENCES

Carbones de Cerrejón, 2003a, Mapa geológico,Cerrejón zona Norte. Scale: 1:50000

Carbones de Cerrejón, 2003b, Stratigraphic Columnsfor the Cerrejón deposit- Patilla section. Scale:1:2000

Dorobek, S. L., 1995, Synorogenic carbonate platformsand reefs in foreland basins: controls onstratigraphic evolution and platform/reefmorphology, in Dorobek, S. L., and Ross, G. M.,eds., Stratigraphic evolution of foreland basins:,SEPM Special Publication 52, p. 27-147.

Etayo-Serna, F., 1979, Moluscos de una capa delPaleoceno de Manantial (Guajira): Boletín deGeología, v. 13 (27), p. 5-55.

Haught, L., Colley, B., & Belding, H., 1944, Geology ofthe Cesar - Rancheria Valley and Commissary ofGuajira: Geological report Tropical Oil Company.

Holz, M., Kalkreuth, W., & Banerjee, I., 2002,Sequence stratigraphy of paralic coal-bearingstrata: an overview: International Journal of CoalGeology, v. 48, p. 147-179.

Jaramillo, C., 2002, Response of tropical vegetation toPaleogene warming: Paleobiology, v. 28, p. 222-243.

Jaramillo, C., & Dilcher, D. L., 2000, Microfloraldiversity patterns of the late Paleocene-Eoceneinterval in Colombia, northern South America:Geology, v. 28, p. 815-818.

-, 2001, Middle Paleogene palynology of centralColombia, South America: A study of pollen andspores from tropical latitudes: PalaeontographicaB, v. 258, p. 87-213.

Jaramillo, C., Muñoz, F., Cogollo, M., & Parra, F., inpress, Quantitative Biostratigraphy for thePaleocene of the Llanos Foothills, Colombia:Improving Palynological Resolution for OilExploration: TMS Special Publication.

Kellogg, J. N., & Bonini, W. E., 1982, Subduction of theCaribbean plate and basement uplifts in theoverriding South America plate: Tectonics, v. 1, p.251-276.

Muller, J., Di Giacomo, E., & Van Erve, A., 1987, Apalynologic zonation for the Cretaceous, Tertiaryand Quaternary of Northern South America:American Association of StratigraphicPalynologists Contribution Series, v. 19, p. 7-76.

Pardo, A., Jaramillo, C., & Oboh-Ikuenobe, F., 2003,Paleogene Palynostratigraphy of the EasternMiddle Magdalena Valley: Palynology, v. 27, p.155-178.

Ramos, J. G., 1990, Ambientes de depósitorelacionados con los parámetros de calidad delos carbones del Cerrejón Bloque B[Undergraduate thesis]: Universidad Nacional deColombia.

Traverse, A., 1988, Paleopalynology: New York,Academic Press, 600 p.

Tschanz, C., Marvin, R., Cruz, J., Mehnert, H., andCebulla, G., 1974, Geologic evolution of theSierra Nevada de Santa Marta: GeologicalSociety of America Bulletin, v. 85, p. 269-276.

Ujueta, G., and Llinás, R. D., 1990, ReconocimientoGeológico de la parte mas septentrional de lasierra de Perijá. Geologia Colombiana, v. 17, p.197-209.

Van Andel, T. H., 1958, Origin and classification ofCretaceous, Paleocene, and Eocene sandstonesof western Venezuela: America Association ofPetroleum Geologists Bulletin, v. 42, p. 734-763.

Van der Kaars, W. A., 1983, A palynological-Paleoecological study of the Lower Tertiary coal-bed sequence from El Cerrejon: GeologiaNorandina, v. 8, p. 33-48.

Villamil, T., 1999, Campanian-Miocenetectonostratigraphy, depocenter evolution andbasin development of Colombia and westernVenezuela: Palaeogeography, Palaeoclimatology,Palaeoecology, v. 153, p. 239-275.

G. BAYONA , C. JARAMILLO , M. RUEDA , A. PARDO , A. CHRISTIE & HERNANDEZ, G.

SNSMSP

AMMS

SNSM= Sierra Nevadade Santa Marta

SP= Serranía de PerijáMS= Macizo de SantanderAM= Andes de Mérida

Km

Km

Tm

Tm

Thn

Thn

Tc

Tc

TcTt

Tp

Tpp

Tp

Oca Fault

Rancheria Faul

Cerr

ejon

Faul

Cerrejon Faul

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CC= Cordillera Central

Oca Fault

Km

Thn

Tm

Tc

TtTt

Tt

Tp Palmit o

Tabaco

Cerrejón

Manant ialHat o Nuevo

Molino

1718400 N

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66

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0E 1

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eria

river

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Cerrejón Formation(Paleocene)

Man

antia

lFor

mat

ion

(Pal

eoce

ne)

Hato NuevoFormation(Maastrichtian-Paleocene)

coalsandstone

sandy mudstone-siltstoneclaystone-shales

limestones

meters

Cer

rejó

nF

orm

atio

n(P

aleo

cene

)

Palmito and TabacoFormations

ERV-17954

coal 155

coal 110

WRV-04752

coal 45

WRV-04774

PAT 11238

SIS 07

Figure 1.Regional geologic setting (left)and geologic map (right) of theCerrejón coal mine(modified from Carbones delCerrejón, 2003a)

5 km

Figure 2.Generalized stratigraphic column of theManantial (modified from Haught, et al, 1944)and Cerrejón formation (modified from Carbonesdel Cerrejón, 2003b and Ramón, 1990). Arrowsindicate stratigraphic intervals of wells used inthis study

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326

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7

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FAULT ZONE

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ACCOM. SPACE INCREASESSEDI. SUPPLY DECREASES

ACCOM. SPACE DECREASESSEDI. SUPPLY INCREASES

ACCOM. SPACE CONSTANTSEDI. SUPPLY INCREASES

ACCOM. SPACE CONSTANTSEDI. SUPPLY DECREASES

ACCOM. SPACE DECREASESEDI. SUPPLY INCREASES

met er

COAL BED 105

COAL BED 110

COAL BED 114

COAL BED 115

COAL BED 120

COAL BED 125

COAL BED 130

COAL BED 135

COAL BED 145

COAL BED 150

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COASTALPLAINSCh Ov

TIDALFLATS

La Sp In Sb Pl

SHALLOWMARINE

Mdst Wkst Pkst Grst

C S Vf M Vc 4 64 256mm

9

8

FAULT ZONE

COASTALPLAINSCh Ov

TIDALFLATS

La Sp In Sb Pl

SHALLOWMARINE

Mdst Wkst Pkst Grst

C S Vf M Vc 4 64 256mm

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ION

ACCOM. SPACE INCREASESEDI. SUPPLY DECREASES

ACCOM. SPACE DECREASESSEDI. SUPPLY INCREASES

ACCOM. SPACE CONSTANTSEDI. SUPPLY INCREASES

COAL BED 175

Up

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WELL WRV-04752 coal seam 103-155WELL ERV-17954 coal seam 175

L E G E N D

Planar cross-beddingCurved and Trough cross-beddingWavy bedding

Bioturbation

Fossils

Lenticular bedding

Plane-parallel laminationRipple lamination

Flaser bedding

Intraclast

Coarsening-upward trend of grain size

Fining-upward trend of grain sizeFault

Covered

Sample number and location (petrography)

Mudstone, Siltstone; light color

Conglomerate

Coal

LimestoneSandstone

Claystone, shale, shaly mudstone

Mudstone, Siltstone; dark color

interval of the core with dip values lessthan 20º and consistent (data fromdipmeter log)

Plant remains

Flooding surfaceMajor flooding surface - good for correlation

Coal bed number (red=transgressive; blue=regressiveblack-unidentified)

Ferruginous bands and nodules

Ch- channel-f ill deposit s in f luvial set t ings (sandst one)

Ov- overbank, crevasse splays and sand sheet sdeposit s in f lood plains (mixed sandst one andsilt st one, mudst one, paleosols)La- subaqueous coast al-lagoon, ponds ( fossiliferousshale, shale)

Sp- suprat idal f lat s, mud f lat s, t idal creeks (silt st one,mudst one, paleosols)

In- int ert idal f lat s, t idal creeks (het erolit hic andrhyt hmit e sandst ones and silt st ones; sandst ones)

Sb- subt idal, shallow-marine clast ic deposit s

Pl- subt idal, shallow carbonat e plat form

Paleosols

Figure 3.(this and next page) Description and interpretationof cores. See Figure 2 for stratigraphic location ofwells. Palynological samples in wells WRV 04752and WRV 04774 are located aprox. each 3 meters.Each column shows the location of the nine surfac-es of stratigraphic correlation and palynologicalbiozones.

COAL BED 103BCOAL BED 105

COAL BED 95

6

219.2

5

CER

REJ

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G. BAYONA , C. JARAMILLO , M. RUEDA , A. PARDO , A. CHRISTIE & HERNANDEZ, G.

4

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ACCOM. SPACE DECREASESSEDI. SUPPLY INCREASES

ACCOM. SPACE INCREASESSEDI. SUPPLY DECREASES

ACCOM. SPACE DECREASESSEDI. SUPPLY INCREASES

145.4

279.4

312.7

336

221.8

199.1

COAL BED 45

COAL BED 50

COAL BED 57

COAL BED 60

COAL BED 65

COAL BED 71

COAL BED 75

COAL BED 80

COAL BED 83

COAL BED 85

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COAL BED 103

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C S Vf M Vc 4 64 256mm

3

WELL WRV-04774 coal seam 045-110

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ACCOM. SPACE DECREASESSEDI. SUPPLY INCREASES

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PAT-131.5

PAT-133

COAL BED 30

WELL PAT-11238 coal seam 030-040

COASTALPLAINSCh Ov

TIDALFLATS

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SHALLOWMARINE

Mdst Wkst Pkst Grst

C S Vf M Vc 4 64 256mm

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G. BAYONA , C. JARAMILLO , M. RUEDA , A. PARDO , A. CHRISTIE & HERNANDEZ, G.

0.1 mm 0.1 mm

G

ChCh

ChCh

QmQm

M

Figure 5.Photomicrographs (parallel and cross nicols, left and right, respectively) of sandstones of the Cerrejon Formation withcontrasting composition. A and B) Very fine to lower fine subarkose with glauconite, G, (< 1%). Very-fine grainedglauconite fragments are either coated by oxides or are filling pores. Other framework grains are of chert (Ch),monocrystalline quartz (Qm) and micas (M). Interstitial material consists of calcite and oxides. C and D) Fine tomedium grained feldspathic litharenite showing myrmekite (quartz and feldspar overgrowth) and quartz-feldsparaggregate grains (Lp), which are indicators of provenance from plutonic rocks. Fragment Lu corresponds to a finelycrystalline grain that may be product of feldspar alteration or devitrification of felsic vitric tuff. Other framework grainsare largely crystalline polycrystalline quartz (Qp), metamorphic (Lm) and sedimentary (Ls) lithic fragments.

LpLp

Lu LuLmLm

LmLm

P P

LpPLpP

LsLs

QpQp

Sample EWP-10, coal seam 45 - 5 meter, Qt83%F10%L7%

Sample 9B, coal seam 45 + 80 m, Qt50%F26%L24%

A B

C D

coal seam 65

coal seam 45

flaser-wavylaminatedsandstones

Figure 4.Photos of 1-m-thick cores showing threeexamples of black mudstones andshales, some with fossils, resting uponcoal seams. In A, tidal-flat sandstonesoverlies the bed of mudstone. Deposi-tion of dark and fine-grained depositsare interpreted as events of flooding.

black shales

F.S.

F.S.

black mudstone

F.S.

coal seam 71

fossiliferousblack shaleand mud-stone

G. BAYONA , C. JARAMILLO , M. RUEDA , A. PARDO , A. CHRISTIE & HERNANDEZ, G.

PLATE 1All samples from core WRV04774, specimen locationgiven in England finder coordinates

1. Echitriletes. Cerrejon 94,41. L15/1,2.2. Echitriletes. Cerrejon 175,75. S22/4.3. Echitriletes. Cerrejon 221,09. E30/2.4. Foveotriletes sp. 1 of Jaramillo and Dilcher 2001.Cerrejon 264,94. J30/1.5-6. Ischyosporites problematicus. Cerrejon 118,25. J16.7. Retitriletes “cristatus”. Cerrejon 81,08. L18/3.8. Retitriletes “cristatus”. Cerrejon 70,08. V32/1.9. Laevigatosporites sp. 1 of Jaramillo and Dilcher 2001.Cerrejon 330,65. Q22/4.10. Laevigatosporites tibuensis. Cerrejon 301,88. E26/4.11. Laevigatosporites tibuensis. Cerrejon 151,82. K37/2.12. Baculatisporites sp. Cerrejon 301,88. O28/2.13. Baculatisporites sp. Cerrejon 310,3. R37/3.14. Psilatriletes > 50 mic. Cerrejon 116,82. J36/4.15. Psilatriletes 25-50 mic. Cerrejon 122,47. L15.16. Verrutriletes “viruelensis”. Cerrejon 46,75. P29/1.17. Camarozonosporites sp. Cerrejon 148,50. Q30.18. Camarozonosporites sp. Cerrejon 91,38. F20.19-20. Camarozonosporites sp. Cerrejon 310,3. V34/4.21. Camarozonosporites sp. Cerrejon 150,45. W32/1.22-23. Retitriletes sp. Cerrejon 310,3. X48/3.24. Trilobosporites sp. Cerrejon 46,75. E24/2.25. Striatriletes sp. Cerrejon 104,56. D26/1.

PLATE 2All samples from core WRV04774, specimen locationgiven in England finder coordinates

1. Araucariacites sp. Cerrejon 150,45. G17/3-4.2. Podocarpites sp. Cerrejon 278,12. H18/2.3. Ephedripites vanegensis. Cerrejon 273.50. R16.4. Ephedripites vanegensis.Cerrejon 151,82. F36/4.5. Ephedripites vanegensis. Cerrejon 166,80. D28/3-4.6. Ephedripites vanegensis. Cerrejon 150,45. G35/1-2.7. Tetradites “psilatus”. Cerrejon 239,29. H30.8. Tetradites “reticulatus”. Cerrejon 96,65. X27.9-10. Aglaoreidia? foveolata. Cerrejon 328,6. J18/2.11. Mauritiidites franciscoi franciscoi. Cerrejon 184.55 ;K22.12. Mauritiidites franciscoi pachyexinatus. Cerrejon171.57 ; F21/2.13. Psilamonocolpites “marginatus”. Cerrejon 36.55 ;T52/1.14. Psilamonocolpites medius. Cerrejon 112.90, X29/215. Psilamonocolpites medius. Cerrejon 252.66 ; P33.16. Racemonocolpites racematus. Cerrejon 225.91.D15/2.17. Retimonocolpites sp. Cerrejon 118.25 ; F33/1.18. Proxapertites cursus. Cerrejon 38.63. R24.19-20. Proxapertites cursus. Cerrejon 216.9. K16/2.21. Proxapertites magnus. Cerrejon 301, 88. T37/2.22. Proxapertites operculatus. Cerrejon 36.55. P62/2.

PLATE 3All samples from core WRV04774, specimen locationgiven in England finder coordinates

1. Proxapertites operculatus. Cerrejon 112.90. J30/4.2. Proxapertites operculatus. Cerrejon 252.66. L35/1.3. Proxapertites psilatus. Cerrejon 252.66. M34/2.4. Longapertites vaneendenburgii. Cerrejon 94.41.S16/2.5. Psilamonocolpites operculatus. Cerrejon 19; T55.6. Spinizonocolpites echinatus. Cerrejon 184.55 ; P19/1.

7. Syncolporites lisamae. Cerrejon 66,15. K28/4.8. Syncolporites lisamae. Cerrejon 15,05. E59/1.9. Retitricolpites “grandis”. Cerrejon 19. S52/4.10. Retitricolpites “communis”. Cerrejon 216,9. V19.11-12. Bombacacites “pasivus”. Cerrejon 252,66. T31-2.13. Foveotricolpites perforatus. Cerrejon 66,15. W22/3-4.14. Psilatricolpites sp. Cerrejon 216,9. S33/4.15. Ctenolophonidites lisamae (ecuatorial view). Cerrejon216,9. H28.16. Ctenolophonidites lisamae (polar view). Cerrejon36.55. G60.17. Gemmastephanocolpites gemmatus. (polar view).Cerrejon 255,35. S28.18. Gemmastephanocolpites gemmatus. (ecuatorialview). Cerrejon 151,82. K37/3.19. Gemmastephanocolpites gemmatus. (ecuatorialview). Cerrejon 255,35. M34/2.20. Psilastephanocolpites globulus. (polar view) Cerrejon285,08. O35/3.21. Psilastephanocolpites globulus (ecuatorial view).Cerrejon 285,08. U27/3-4.22. Psilastephanocolpites globulus. (ecuatorial view).Cerrejon 310,3. T36/2-4.23. Psilastephanocolpites sp. Cerrejon 46,75. J37/1.24. Stephanocolpites “scabratus”. Cerrejon 330,65.C27/4.25. Stephanocolpites sp. Cerrejon 36,55. E58/1.26-27. Brevitricolporites sp. Polar view. Cerrejon 107-108,85. W34/1.28. Brevitricolporites sp. Cerrejon 287,52. Q27/4.29. Brevitricolporites sp. Cerrejon 347,54. E44/3.30. Foveotricolporites sp. Cerrejon 116,82. X29/4.31. Foveotricolporites sp. Cerrejon 116,82. H37.

G. BAYONA , C. JARAMILLO , M. RUEDA , A. PARDO , A. CHRISTIE & HERNANDEZ, G.

G. BAYONA , C. JARAMILLO , M. RUEDA , A. PARDO , A. CHRISTIE & HERNANDEZ, G.

G. BAYONA , C. JARAMILLO , M. RUEDA , A. PARDO , A. CHRISTIE & HERNANDEZ, G.

G. BAYONA , C. JARAMILLO , M. RUEDA , A. PARDO , A. CHRISTIE & HERNANDEZ, G.