CBTH Researchers at AAPG 2013

• TITLE: Fracture Identification and Analysis Using Seismic Attributes in Carbonate Reservoirs: Cimarrona Formation, Middle Magdalena Valley Basin, Colombia
  AUTHORS: Joan M. Blanco (1), Crelia E. Padrón (1), Hugo I. Contreras (2)
  INSTITUTIONS: 1. Earth Sciences Department, Universidad Simón Bolívar, Caracas, Venezuela. 2. Schlumberger Information Solutions, Caracas , Venezuela.
  ABSTRACT: Use of seismic attributes for fault and fracture detection below the resolution of conventional seismic data is one of the major goals of modern seismic interpretation. Key attributes used for fault and fracture mapping include: dip-magnitude, dip-azimuth, coherence, volumetric curvature, and ant tracking. Fracture characterization is a matter of great practical importance in the recovery of hydrocarbons because fractures provide a major control on oil flow within carbonate reservoirs. We use some of these attributes to describe a naturally fractured carbonate reservoir of the Cimarrona Formation in the Middle Magdalena Valley Basin (Colombia). The field is primarily located on the eastern flank of a large north-south trending syncline. Two fault trends have been previously identified: 1) N-S-striking thrust faults; and 2) NW-SE and NE-SW-striking, strike-slip and oblique-slip faults. Attributes enhance these patterns and allow characterization of fracture density, orientation, and type of fluid saturation, using a 3D post-stack time migrated seismic volume integrated with well data. We use ant tracking performed on discrete frequency cubes in co-blending visualization, spectral decomposition in RGB display, and a tool for automated extraction of faults and fractures, to discover fractured areas at different frequencies. We identify and analyze fracture zones in the discrete frequency ants cubes, then, using diverse diagrams (rose diagram, histogram, cumulative frequency plot) we correlate dipmeter data with the fractures extracted automatically from anttracking. This workflow enhances the resolution of faults and fractures, corroborating fracture sets and patterns previously reported. Moreover, t*attenuation and sweetness attributes were also calculated to assist in the fault fluid saturation and sand detection, respectively.



• TITLE: 2D Seismic Interpretation of the Tumaco Basin, SW Colombia. Implications for Tectono-Stratigraphic Evolution and Hydrocarbon Exploration.
  AUTHORS: Luisa F. Campino (1), Alejandro Escalona (1)
  INSTITUTIONS: 1. University of Stavanger, Stavanger, Norway.
  ABSTRACT: The Tumaco on and offshore basin is located in the Pacific region of NW corner of South America, southwestern Colombia. It is classified as a forearc basin and it is considered a frontier exploration basin. The basin was formed during Paleogene-Recent convergence of oceanic derived terranes against South America. The stratigraphy consists of a volcano-clastic basement overlie by an Eocene to Recent clastic sedimentary cover. The last exploratory well, drilled in the 80’s, showed non-commercial amounts of oil and gas. This study integrates new onshore outcrop data (e.g. biostratigraphy, petrography, geochronology, and organic geochemistry) with more than 3000 Km of 2D seismic data on- and offshore in order to better understand the main basement terranes, its control on basin evolution and the hydrocarbon potential within the context of the Caribbean plate evolution in the region. Preliminary results based on seismic interpretation, plate tectonic models and surface geology indicate that the basement high, the Remolinogrande high, is the continuation of the Gorgona large igneous province to the north, which was accreted in the Late Eocene during subduction of the Farallon plate beneath South America. This accretion resulted in the development of the Tumaco onshore basin, located between the Remolinogrande high and the Western Cordillera of Colombia. To the south, the region may correlate with arc and oceanic terranes that outrcrop in the Ecuador region (San Lorenzo and Piñon tarranes), that were accreted during subduction of the Caribbean plate beneath South America in the Paleogene. The Tumaco offshore basin seems to be the forearc basin that results of the subduction of the Nazca plate beneath South America. The subduction affected the entire region, resulting in continuous uplift of the Remolinogrande high. Eocene-Recent basin infill of the Tumaco onshore basin occurred mostly from the Western Cordillera of Colombia with the development of deep marine to continental deposition, whereas the Tumaco offshore consists of mostly marine sedimentation since Miocene. Source rocks mostly include Eocene marine shales in the Tumaco onshore basin that are buried today to a depth of 8 km. Reservoir rocks include marine and continental sandstones of Paleogene and Miocene age. Because the Tumaco basin has a sag type basin configuration most of the traps are pinchouts against the uplifted Remolinogrande high and stratigraphic traps.



• TITLE: Petroleum prospectivity of the southwestern Nicaraguan Rise (Colombian Caribbean) based on regional integration of seismic and well data
  AUTHORS: Luis Carlos Carvajal Arenas (1), Paul Mann (1), Mike Saunders(2)
  INSTITUTIONS: 1. Earth and Atmospheric Sciences, University of Houston, Houston, TX, United States. 2. Spectrum Geo Inc., Houston, TX, United States.
  ABSTRACT: The southwestern Nicaraguan Rise (SWNR) represents a vast (213,000 km2), underexplored part of the Caribbean where, since the early 1980s only two exploratory wells have been drilled to shallow depths (<2 km). To reevaluate the prospectivity of this area, we have used 2,500 km of vintage 2D seismic data acquired in the early 1980s and 3,000 km of high-resolution, deep-penetration 2D seismic data acquired in 2007. The 2007 data is tied to the two existing exploration wells and two ODP wells drilled in 1996 containing a complete set of logs and paleo ages. We have also integrated our interpretation with previous work by Bowland (1993) using UT lines from the early 1980s that effectively expands our study area to cover a 621,000 km² area of the SWNR and Colombian basin in offshore Costa Rica and Nicaragua. Results include: 1) All three areas share a common Caribbean oceanic plateau basement erupted over a broad area in Turonian time (~90 Ma); 2) The late Cretaceous-Paleocene interval (84 m) overlying basement is a pelagic calcarenite-dolomite with TOC values as high as 10% in DSDP wells drilled in the 1970s in the Venezuelan basin, and this interval thins against numerous basement seamounts and highs reflecting continued igneous extrusions during the late Cretaceous; 3) The Middle Eocene-Middle Miocene interval varies widely in thickness (500-650 m) partly in response to its infilling of a rough, magmatically-controlled seafloor; these localized basins range in depth from 3,000 m to 8,000 m; this Cenozoic unit contains known source rocks from wells drilled in Nicaragua with TOC>2 and S2>5; this unit is also known to be mature with a fair to very good generation potential (for both gas and oil); sandstone within this unit, mainly derived from Central America, may also act as reservoirs; and 4) Middle Miocene to Holocene rocks are shallow water carbonate caps or peri-platform deposits with potential porosity and reservoir potential.



• TITLE: Crustal Structure of the Central Atlantic Rifted-Passive Margin from South Carolina to the Southeastern Bahamas: A First Step to Understand its Petroleum Potential
  AUTHORS: Alex Dale (1); Paul Mann (1); Dale Bird (1)
  INSTITUTIONS: 1. University of Houston, Houston, TX, United States
  ABSTRACT:The conjugate margins of the eastern North America and northwestern Africa are widely recognized as volcanic rifted margins of Triassic-Jurassic. Wide-angle geophysical experiments in the early 1990’s in the Carolina trough area of South Carolina illustrated evidence for a typical Mesozoic volcanic passive margin ranging from 5 to 10 km emplaced on thinned continental crust and extending from this area over 800 km along the eastern margin of the North America. Modern refraction studies have not been carried out further south of the Carolina trough to reveal the crustal structure of the Atlantic margin of the Florida peninsula and the Bahamas carbonate platform. Collectively, the eastern Florida-Bahamas margins form a passive margin segment of over 1800 km in length with little exploration and no commercial hydrocarbons discovered to date. In this study we present five gravity models for transects ranging from 800-1300 in the margin dip direction and one 1900-km-long, margin-parallel transect from northern Florida to the tip of the southeastern Bahamas. The data used includes 6km spaced gridded DNAG, free-air, and Bouguer-corrected data. Model constraints include widespread explosion seismic refraction data from 1960s and 70s, three deep exploration wells, and magnetic data to enhance depth-to-basement estimations. Results include: 1) reoccupation of Carolina trough wide-angle transect from early 1990s: Gravity model matches closely with refraction profile and shows a lower crustal body consistent with a volcanic origin; sediment thicknesses range from 5-10 km; 2) Central Florida; 12km; 3) Northern Bahamas: 5-10km; 4) Central Bahamas: 5-7km; 5) Southern Bahamas: 5km of a more dense crust, interpreted as transitional-oceanic type; and 6) Florida to Bahamas: continental crust (2.7g/ccm) thins from 15km to 5km and to a more dense (2.8 g/ccm) crust near Turks and Caicos. The volcanic passive margin character of all transects is consistent with their origin as part of the Central Atlantic Magmatic Province from the Triassic age to the Mesozoic. Along-strike variations in sediment thicknesses and estimated heat flow values of a volcanic passive margin are used to calculate maturity of an inferred late Jurassic source rock deposited along the length of the margin.



• TITLE: Worldwide Trends in the Discoveries of Giant Fields from 2006-12 with Predictions on the Locations and Numbers of Future Giants
  AUTHORS: Paul Mann (1), Naila Dowla (1)
  INSTITUTIONS: 1. University of Houston, Houston, TX, United States
  ABSTRACT: We use a compilation of over 1300 articles and news releases to document the addition of 40 new oil giants and 36 new gas giants during the period of 2006-12. These newest giants bring the world's total count of giant fields to 1039 which collectively make up about half of the world's conventional hydrocarbon reserves. The number, size and ratio of oil and gas giants diverge significantly from the long-term, post-1965 decline curve for giants. The number of gas giants is steadily rising relative to the number of oil giants. We attribute this spike in giant discoveries to technological improvements including improved efficiencies in deep-water exploration. The basinal setting for the 76 new giants in the 2006-12 period is consistent with our 2003 study of the most giant-prone oil and gas basinal settings. The majority of the 2006-2012 discoveries are found along continental passive margins fronting major ocean basins (13 in Brazil, 9 in east Africa, 7 in west Africa, 5 in the Gulf of Mexico, 3 in the North Sea, 2 in Australia, and 1 each in India and China). Far fewer giants were found in rift and inverted rift settings (2 in South East Asia, 1 each in North Africa and China) and on continental and arc collisional margins ( 9 in Russia, 2 in northern South America). Extrapolating trends seen in 2006-11, we predict that: 1) about 80 oil and gas giants will be discovered in the period from 2013 to 2020; 2.) two thirds of those giants will be gas; 3) three quarters of all giant discoveries will be offshore; 4) upcoming giant discoveries will cluster on known or emerging clusters on the western and eastern margins of Africa, North Sea, Barents Sea, Siberia, eastern Mediterranean Sea, Persian Gulf, and the Caspian Sea.
  
  SESSION TITLE: Theme 3: Applied Technologies for Regional Play Analysis (AAPG)
  SESSION TYPE: Poster
  SESSION LOCATION: Exhibition Hall
  SESSION DAY & DATE: Tuesday, May 21, 2013
  SESSION ABSTRACT START TIME: 8:30 AM
  SESSION ABSTRACT END TIME: 12:00 PM



• TITLE: Petroleum Potential of Onland Basins in Hispaniola (Dominican Republic and Haiti) Based on Integration of Vintage Well and Seismic Reflection Data with Geochemical Data
  AUTHORS: Johnathon Osmond (1), Paul Mann (1), Stephen Pierce (2)
  INSTITUTIONS: 1. Department of Earth & Atmospheric Sciences, University of Houston, Houston, TX, United States. 2. Mertz Energy, Houston, TX, United States.
  ABSTRACT: GPS studies of Hispaniola show that maximum oblique plate convergence is centered between the Caribbean and North America plates. The onset of oblique collision occurred in late Miocene time and is responsible for forming thrust-bound ramp basins. To characterize hydrocarbon systems in south-central Hispaniola, we assess five Neogene stratigraphic units for petroleum generation potential and likelihood of petroleum retention by structural traps. Natural oil seeps and small-production oilfields in the region confirm the presence of working hydrocarbon systems, but previous work does not characterize the systems nor constrain their scale or capacity. Poor TOC values are associated with most Cretaceous to Neogene rocks in the Dominican Republic, however, middle Miocene Sombrerito Formation rocks show marginal petroleum generative potential. Reservoir rocks for the Maleno and Higuerito oilfields are the late Miocene submarine fan-deposited Trinchera sandstone and reefal facies of the Sombrerito limestone. Aeromagnetic data suggests a belt of Plio-Pleistocene volcanic rocks to the west with shallow intrusives beneath the two oilfields may have facilitated oil maturation. We suggest the possibility that thrusting of sabkha like organic rich facies of the Sombrerito limestone may also have played a role. The high sulfur contents, C-13 abundances, and pristine phytane ratio of the oilfield samples suggest an origin of mixed terrestrial and algal materials in a restricted carbonate marine environment. Seals are likely to be the shaly interbeds in this submarine fan sequence. Seismic data suggest structural traps linked to the Maleno and Higuerito oilfields are a large east-west anticline and thrust folds associated with the post-late Miocene formed Los Pozoz Fault. The steeper limbs of these anticlines reflect southwestward overthrusting of the Cordillera Central block over the Azua basin. Seeps at Higuerito indicate that faulting has compromised the structural trap. Late Cretaceous Hatillo limestone from eastern Hispaniola, Ocoa Bay beach tar, and DSDP samples from the Caribbean Sea have smaller C-13 abundances than the Higuerito and Maleno oils, indicating the Ocoa Bay and Hatillo source rocks have a different origin. Areas of western Azua basin and Enriquillo basin infer an open ocean pelagic setting while outcrop observations and oil geochemistry indicate a Sombrerito source deposited.



• TITLE: Crustal Provinces of the Nicaraguan Rise as a Control on Source Rock Distribution and Maturity
  AUTHORS: Bryan Ott (1), Paul Mann (1), Mike Saunders (2)
  INSTITUTIONS: 1. Earth and Atmospheric Sciences, University of Houston, Houston, TX, United States. 2. Spectrum Geo Inc., Houston, TX, United States.
  ABSTRACT: The offshore Nicaraguan Rise in the maritime zones of Honduras, Jamaica, Nicaragua and Colombia covers a combined area of 500,000 km², and is one of the least explored carbonate regions of late Cretaceous-Cenozoic age remaining on Earth. The purpose of this study is to describe the Cretaceous to Recent tectonic history of the deep-water Nicaraguan Rise, and to better understand how different types of tectonically-juxtaposed crustal blocks are overlain by distinctive Eocene to Recent source rocks. We interpreted 8700 km of modern, deep-penetration 2D seismic data tied to five wells that penetrated the top of late Cretaceous igneous basement. Combining these seismic data with gravity, magnetic and crustal refraction data, we define four, fault-bounded crustal provinces for the offshore Nicaraguan Rise: 1) a thicker (15-18 km) Late Cretaceous Caribbean ocean plateau (COP) with rough, top basement surface; 2) normal (6-8 km) Late Cretaceous COP with smooth top basement surface (B") and with correlative outcrops in southern Haiti and Jamaica; 3) Thinned, Precambrian-Paleozoic continental crust (22-24 km thick) with correlative outcrops in northern Central America; and 4) Cretaceous arc crust (>18 km thick) with correlative outcrops in Jamaica.
  Three source rock families have been identified from oil or gas shows in ten, on- and offshore Jamaican wells: 1) Oxfordian, marine source rock equivalent to the Smackover formation of the northern Gulf of Mexico; 2) Maestrichtian, marine source rock; 3) Eocene aged mixed marine/terrestrial Chapelton formation of Jamaica (also known as the Guy’s Hill formation). The Chapelton formation sampled in the Content -1 well contains an average total organic carbon (TOC) value of 3.97%, and is the highest quality source rock of all three sources. Tertiary sections of the Chapelton formation that were sampled had not reached depths greater than 2-3 km, making these rocks immature to marginally mature. However, deep rifts up to 9 seconds TWT exist in the immediate offshore areas of Jamaica, and form likely sweet spots for mature source rocks. Late Cretaceous and Eocene source rocks are similar in Jamaica and Honduras, and may form a sheet-like deposit across the Nicaraguan Rise. Light oil and gas shows of similar ages have been identified in the Main Cape -1 and Miskito -1 wells, and may be linked to widespread source rock deposition on the Nicaraguan Rise.



• TITLE: Structural Evolution and Petroleum Potential of Putumayo Foreland Basin, Colombia, from Subsurface Mapping and 3D Flexural Modeling
  AUTHORS: Luis F. Pachon (1), Paul Mann (1), Néstor Cardozo (2)
  INSTITUTIONS: 1. Earth and Atmospheric Sciences, University of Houston, Houston, TX, United States. 2. University of Stavanger, Stavanger, Norway.
  ABSTRACT: The Putumayo foreland basin (PFB) covers 28,000 km² of southernmost Colombia and forms a 250-km-long segment of the 7000-km-long corridor of late Cretaceous-Tertiary foreland basins formed by the eastward thrusting of the Andean mountain chain over Precambrian cratons of South America. The current daily production of the Putumayo basin is ~90K bopd barrels of 15-35 API oil and 300K bopd of 20-35 API oil in the contiguous foreland basin to the south in Ecuador. This study uses ~4000 km of 2D seismic data tied to 17 exploratory wells to describe the structure and stratigraphy of the PFB. The wedge-shaped basin stratigraphy is used to model the lithospheric flexural deflection. PFB resides adjacent to the Andes adjacent to the active Pacific subduction margin of South America and has been subject to collision and shallow subduction events. Based on mapping of the subsurface of the PFB and comparison with published works from the southward continuation of the PFB into Peru and Ecuador, we propose three main across-strike, structural provinces for the PFB: 1) the 20-km-wide, eastern Orito zone is characterized by inverted half-grabens with structural relief produced during the Late Miocene; the best expressed, inverted rift is the Orito mountain front structure that exhibits more than 300 m of reverse fault throw of Tortonian age; 2) the 45-km-wide, central zone is characterized by inverted normal faults of the same age as the western area but these faults exhibit only 20 m of reverse fault throw and are commonly of Paleocene age; and 3) the 120-km-wide, eastern zone is characterized by the 90-km-wide, N-S trending Caquetá arch with only a few slightly inverted normal faults at its crest; the basement of the Caquetá arch composed of deformed Paleozoic sedimentary rocks. We used 3D flexural modeling to backstrip foreland basin units from Cretaceous to recent age; this analysis yields two pulses of rapid, foreland-related subsidence in the Eocene and Miocene. Despite present-day oblique thrusting at the mountain front, arching of the PFB basement using a standardized elastic thickness is pronounced and reveals a peripheral bulge that acts as the updip limit for most oil in the basin. Modeling predicts that the modern forebulge occupies the Caquetá arch and the zone of maximum flexure has been along the western area of the central zone since Oligocene. Profiles are used to illustrate possible traps in the basin that may have been overlooked.



• TITLE: Buried Cretaceous Delta of the Barreirinhas Basin, Offshore Brazil: Potential Source of Structural and Stratigraphic Traps in Deepwater Sandstone?
  AUTHORS: Kyle Reuber (1), Paul Mann (1), Mike Saunders (2)
  INSTITUTIONS: 1. Earth and Atmospheric Sciences, University of Houston, Houston, TX, United States. 2. Spectrum Geo Inc., Houston, TX, United States.
  ABSTRACT: The Barreirinhas Basin, offshore Brazil is a major focus for recent oil and gas exploration. Previous exploration efforts in the basin were focused on structural traps at the shelf edge that have yielded no major discoveries to date. In this complex structural framework of the Barreirinhas Basin, I use 6,500 km of recently acquired seismic reflection data to show mapping evidence for a wedge-shaped, seaward tapering basin floor fan as a component of a larger 15,500 km² deltaic system, which ranges in thickness from 1,000-3,000 m in 1,000-2,500 m of water. The basin floor fan deposits of Campanian age are located in the same area as the modern Mearim River, which presently has limited flow and a small delta. These deposits may have been part of a larger drainage network that included a sediment bypass into deeper water across the steep, strike-slip-controlled equatorial margin of Brazil. Isochron maps of the mounded basin floor fan units show well defined fan and lobate shapes whose apices project to plus or minus 200 km to the location of the modern Mearim River. By the deposition of basin floor fans in Campanian time, the underlying source rocks of Albian-Cenomanian age (Caju Group) were deposited as a sheet like mass. Overburden above the Caju Group totals 3-4 km of mainly clastic rocks, and Petromod calculations place these source rocks in the oil window. The proposed play in the Barreirinhas basin is compared to similar successful oil plays on its conjugate margin in Ghana, West Africa.



• TITLE: Late Cretaceous to Cenozoic deformation of the North American-Caribbean plate boundary in northern Central America and its effects on the origin and migration of hydrocarbons
  AUTHORS: Javier Sanchez (1), Paul Mann (1), Pete Emmet (1)
  INSTITUTIONS: 1. Earth and Atmospheric Sciences, University of Houston, Houston, TX, United States.
  ABSTRACT: The northern part of Central America represents a complex plate boundary zone that has undergone multiple phases of extension and convergence as the transition from Late Cretaceous-earliest Cenozoic collision to Cenozoic transtension controlled faulting and basin formation in the Honduran borderland region. We interpret 5935 km of 2D seismic tied to 13 wells, structural and potential fields modeling, and several 1D subsidence models to illustrate the effects of collision to strike-slip transition on oil generation and migration in this shelf, slope and deep water area. The Cenozoic strike-slip/transtension phase is characterized by growth (syntectonic) and a post-rift extensional period since Paleocene that produced ~5% of extension calculated on a section normal to the plate boundary. Two types of normal faults are observed: 1) low-angle (30-40°) faults with high displacements (1500-3500 m) and 2) high-angle (50-70°) with smaller displacements (100-500 m). The first type of normal faults are thick-skinned and possibly detached along the base of crust, where the block rotation produced by their listric and ramp-flat geometry controls the formation of small, rift basins. These faults are related to inversion of preexisting Late Cretaceous thrusts that record 30 % of shortening. The second type of normal faults mainly deform the Cenozoic section and can be related to the accommodation of regional extension, folding and flexure related to thermal sagging. Because the current vector of Caribbean plate motion is oblique by ~5° to the North American-Caribbean plate margin, we assume that the main stress direction is controlled by left-lateral, strike-slip kinematics. Assuming a linear proportion between plate displacement rate (~15-20 mm/yr) and the observed fault deformation, we calculated that the Cenozoic strike-slip component was twelve times larger (~60%) than the dip-slip deformation. La Cretaceous-Paleocene source rocks known in the area may have matured by late Eocene time especially in the thicker basins of the Honduras borderland.



• TITLE: Tectonic effects on changing fluvial style in the Late Eocene ‐Oligocene northern Llanos foreland basin of Colombia
  AUTHORS: Lucia Torrado (1), Paul Mann (1), Janok Bhattacharya (1)
  INSTITUTIONS: 1. Earth and Atmospheric Sciences, University of Houston, Houston, TX, United States.
  ABSTRACT: The Llanos foreland basin (LFB) of Colombia is the country's most prolific oil producer with most known oil fields found in anticlines bounded by normal faults. The objective of the study is to assess the reservoir potential of the Late Eocene‐Oligocene Carbonera Formation, a 400‐1800‐m‐thick reservoir unit of fluvial deposits with many areas of unexplored stratigraphic traps related to unfaulted, sandfilled fluvial channels. We integrated 700 km² of 3D seismic data volumes with 9 wells in the eastern Casanare province near the Jordan oil field. Interpretation of reservoir distribution included gamma ray facies analysis of wells combined with interpretation of multiple 3D attributes including coherence, curvature and spectral decomposition. Well analysis shows that of the eight members of the Carbonera Formation, two members, C7 and C1, are clean, well‐sorted fluvial sandstone with porosities up to 20%. Mineralogy, plant debris and coals indicate floodplain aggradation in members C8, C6, C4 with brackish water indicating fluvial connectivity to the Caribbean Sea. Correlations between wells and attribute maps show that the Carbonera Formation represents a tidally‐influenced fluvial deposit within straight to meandering channel belts seen on seismic as strong, high‐amplitude, concave reflections in the seismic. On seismic time slices, channel belts exhibit: 1) moderate width to depth (W/D) ratio and high sinuosity for the main drainage; 2) low to moderate width to depth (W/D) ratio and low sinuosity for the tributary channels; 3) a decrease of sand content in the middle members of the formation; and 4) wider channels with thicker floodplain deposits and localized sand bodies in members C5 and C3. Well subsidence curves show an increase of total subsidence due to the initial uplift of the Eastern Cordillera in Oligocene time and eastward widening of the basin. The source area shifted from the Guyana Shield to the east represented by the members C7 and C5, to a source area produced by the uplift and erosion of the Eastern Cordillera to the west, represented by the members C3 and C1. Flattened time slices show changes in paleoflow directions of rivers from southwest to northeast, controlled by the eastward migration of the flexural high of the LFB in the Late Eocene–Early Oligocene, to a NW to SE direction of flow in the Middle Oligocene that likely corresponds to the development of tributaries feeding a larger axial fluvial system. Increases in short‐lived accommodation space of the LFB led to large embayments produced by the upward flow of brackish waters up the main fluvial system from the Caribbean Sea.