Lower Congo Research Articles

Depositional characteristics in the Lower Congo Basin during the Cenomanian-Turonian stage: Insights from fine-grained sedimentary rocks

The Cenomanian-Turonian (C-T) stage, marked by extensive black shales and Oceanic Anoxic Event 2 (OAE 2), is pivotal for deciphering paleoceanographic conditions and the main drivers of hydrocarbon formation. Despite its significant oil and gas potential, the Lower Congo Basin (LCB) in central West Africa, particularly during the C-T stage (Likouala Formation), has been severely understudied, primarily due to limited exploration and a historical preference for other basins. Therefore, understanding the depositional characteristics of the C-T stage in the LCB is essential for elucidating paleoceanographic conditions, evaluating hydrocarbon potential and interpreting environmental changes. Due to the limited availability of published data and samples, we employed a targeted and integrated geological analysis to gain comprehensive insights, encompassing logging, lithofacies identification, thin-section observations, grain size measurements, and geochemical analyses (major, trace, and rare earth elements), to provide a cohesive and confirmatory assessment. Utilizing relative sea-level curves and geochemical indicators, and by comparing with other relevant basins, this study preliminarily identified OAE 2 stratigraphic intervals and attempted to discuss the impact of OAE 2 on organic matter enrichment in the LCB. The results indicate that, during the C-T stage, the LCB featured a restricted sea bay environment with limited terrestrial input and anoxic waters. Multiple geochemical proxies suggest that relative sea-level changes significantly affected paleoproductivity, thereby influencing organic matter enrichment. During the depositional period of Lower Likouala Formation (LLF), a relative sea-level drop resulted in weakly reducing conditions in a marginal restricted sea bay environment, leading to low primary productivity. Conversely, during the depositional period of Upper Likouala Formation (ULF), enhanced aeolian input and sea-level rise increased nutrient supply from the open ocean. This led to elevated surface marine productivity and intensified reducing conditions in the water column, forming a marginal semi-restricted sea bay environment. Enhanced reducing conditions within the lower stratigraphic intervals of the ULF are likely consequences of OAE 2. However, the marginal restricted sea bay environment and limited water exchange may have constrained the enhancement of paleoproductivity by OAE 2. These insights not only significantly enhance our understanding of the organic-rich fine-grained sedimentary rocks in the LCB during the C-T stage, but also contribute to a broader comprehension of the South Atlantic's paleoceanographic conditions and the interplay between regional geological processes and global climate events during the C-T stage.

Paleostress evolution of the Outer Kwanza basin (offshore Angola); comparison with the Congo basin and implications for the tectonic history of the Central segment of the West Africa passive margin

This study aims at reconstructing the paleostress history of the Outer (offshore) Kwanza basin (West African passive margin) and at comparing it to stress results acquired further north in the Congo basin. Three oriented borehole cores provided by TotalEnergies and reaching the syn-rift, Barremian-Aptian pre-salt carbonates offshore Angola were investigated. Paleopiezometry based on the Stylolite Roughness Inversion Technique (SRIT) and Calcite Twin Inversion Technique (CSIT) was combined with fracture analysis, U–Pb geochronology of carbonates and burial modelling to unravel the orientations and magnitudes of horizontal and vertical stresses affecting the pre-salt carbonates over time. Calcite twins were measured from a primary sparite matrix, and the inversion process unravelled a polyphase stress history, comprising ∼ E-W and NE-SW extensional trends that we associate to the rifting (130-112 Ma) that led to the opening of the South Atlantic ocean. The ∼ E-W extension is consistent with the early occurrence of N-S striking normal faults which developed in relation to the reactivation of inherited basement structures. This ∼ E-W extension evolved during the Barremian-Aptian (?) into the dominant regional NE-SW extension marked by large-scale NW-SE striking normal faults. The stress history also comprises compressional and strike-slip stress regimes associated with a ∼N-S trending σ1 which can be related to the transfer of orogenic stresses from the distant Africa-Eurasia plate boundary at ∼67-60 Ma. Finally, compressional and strike-slip stress regimes associated with a ENE-WSW to ∼E-W trending σ1 dominated since at least ∼17-15 Ma (possibly ∼34 Ma); they are interpreted as the expression of the mid-Atlantic ridge push. These (paleo)stress results are compared and combined with earlier paleostress reconstructions in the northern offshore Lower Congo basin (also belonging to the Central segment of the margin) and in the onshore Congo basin in order to refine the stress record and the timing of tectonic events since the early Cretaceous, thus providing unprecedented constraints on the tectonic history of the West Africa passive margin. This tectonic history includes both extensional and compressional events, and was driven mainly by far-field stresses, either gravitational or tectonic in origin, which are related to interactions between the African plate and surrounding plates.

The dominant influence of muddy bottom currents on organic-rich fine-grained sedimentary rocks: The lower Congo Basin, west Africa

The Madingo Formation in the Lower Congo Basin (LCB) of West Africa is a fine-grained strata, which is considered to be the most promising source interval during the drift stage. Despite the extensive studies of the internal sedimentary characteristics of the Lower Mading Formation (LMF), muddy bottom currents have not been previously identified in this area. Extensive seismic (2D and 3D data), wire - line measurements and cutting samples in the LCB offer a unique opportunity to study the influence of muddy bottom currents depositional system on organic matter, and related depositional environment of the region and its depositional model of organic rich fine-grained strata. This study aims to unravel the influence of muddy bottom currents on organic matter enrichment within the LMF and build a depositional model. In combination with drilling and thin sections analysis, the M-1 member suggests the initiation and cessation of muddy bottom currents. Utilizing 3D seismic data inversion techniques, geochemical analysis, and sedimentological assessment, we studied the effect of muddy bottom currents on organic matter enrichment from the perspectives of paleoproductivity, preservation conditions, terrigenous input, and total organic carbon (TOC) distribution. Results show that muddy bottom currents have a significant impact on the redistribution of shallow water shelf sediments. They promote the transportation of nutrients and organic matter to deep water shelves, improving paleoproductivity. Most notably, terrigenous input is a key factor affecting organic matter distribution, resulting in dilution effects in deep water shelf bottom current influence areas, but conducive to the preservation of deep organic matter in low-lying areas of shallow water shelf. Muddy bottom currents have a weaker influence on the preservation environment of deep water shelves, but they have a significant effect on redox indicators (eg. U/Th, Ni/Co, V/Cr). Specifically, they reduce the enrichment in particulate elements. We established the depositional models of organic-rich fine-grained sedimentary rocks for the M-1 and M-2 members in LCB. These insights not only provide practical depositional models for marine sources rocks in the LCB, but also improves the general understanding of marine organic matter accumulation in muddy bottom currents environments. Furthermore, they serve as a reference for the study of organic-rich fine-grained sedimentary rocks in similar basins.

Impacts of Quaternary Climatic Changes on the Diversification of Riverine Cichlids in the Lower Congo River.

Climatic and geomorphological changes during the Quaternary period impacted global patterns of speciation and diversification across a wide range of taxa, but few studies have examined these effects on African riverine fish. The lower Congo River is an excellent natural laboratory for understanding complex speciation and population diversification processes, as it is hydrologically extremely dynamic and recognized as a continental hotspot of diversity harboring many narrowly endemic species. A previous study using genome-wide SNP data highlighted the importance of dynamic hydrological regimes to the diversification and speciation in lower Congo River cichlids. However, historical climate and hydrological changes (e.g., reduced river discharge during extended dry periods) have likely also influenced ichthyofaunal diversification processes in this system. The lower Congo River offers a unique opportunity to study climate-driven changes in river discharge, given the massive volume of water from the entire Congo basin flowing through this short stretch of the river. Here, we, for the first time, investigate the impacts of paleoclimatic factors on ichthyofaunal diversification in this system by inferring divergence times and modeling patterns of gene flow in four endemic lamprologine cichlids, including the blind cichlid, Lamprologus lethops. Our results suggest that Quaternary climate changes associated with river discharge fluctuations may have impacted the diversification of species along the system and the emergence of cryptophthalmic phenotype in some endemic species. Our study, using reduced representation sequencing (2RADseq), indicates that the lower Congo River lamprologines emerged during the Early-Middle Pleistocene transition, characterized as one of the earth's major climatic transformation periods. Modeling results suggest that gene flow across populations and between species was not constant but occurred in temporally constrained pulses. We show that these results correlate with glacial-interglacial fluctuations. The current hyper-diverse fish assemblages of the lower Congo River riverscape likely reflect the synergistic effects of multiple drivers fueling complex evolutionary processes through time.

Brittle faulting and tectonic stress history on the western margin of the Congo Basin between Kinshasa and Brazzaville: Implications for the evolution of the Malebo Pool and the Congo River

The history of brittle faulting and associated paleostress states has been investigated in the rapids of the Congo River at the outlet of the Malebo Pool between Kinshasa (Democratic Republic of the Congo) and Brazzaville (Republic of the Congo). The aim of this study was to unravel the Meso-Cenozoic tectonic evolution of the western margin of Central Africa, as well as to investigate the dynamic evolution of the Pool and the capture of the Congo Basin drainage system by the Lower Congo River through the Central African Atlantic swell that formed between the Congo Basin and the Atlantic Ocean. We reviewed the geological evolution of the Pool area using recent data and new field observations to develop a consistent stratigraphic model for both sides of the Congo River. We collected a significant amount of data faults and fractures in the early Paleozoic Inkisi arkosic sandstones, identified four successive data subsets and determined their related paleostress tensors trough an iterative process utilizing relative chronological indications. All paleostress states exhibit a a strike-slip faulting regime, with varying orientation of horizontal principal compression. The timing of faulting was constrained by indirect observations based on the updated understanding of the Pool's evolution. The geodynamic interpretation of the brittle stages considered potential sources of compressional stress arising from plate boundaries and from the oceanic ridge push. A polyphase brittle tectonic history was identified, characterized by the gradual appearance of newly formed faults and reactivation of the existing ones, leading to the gradual saturation of the host rock with fractures. The most recent event let to a significant imprint on the current landscape and is believed to have facilitated the connection of the drainage system of the Congo Basin to the Atlantic coast in the Oligocene period. The current stress state, determined from earthquake focal mechanisms, aligns with the most recent paleostress state identified determined from fault-slip data, displaying similar stress axis orientations but with consistent with a transpressional stress regime instead of a strike-slip one.

Depositional characteristics of fine-grained sedimentary rocks and the links to OAE-3 and PETM of the Upper Cretaceous-Paleogene Madingo Formation, lower Congo Basin, West Africa

Fine-grained sedimentary rocks of the Madingo Formation in the Lower Congo Basin (LCB), are significant targets for Upper Cretaceous–Paleogene depositional system analysis in West Africa. Six types of fine-grained sedimentary rocks of the Madingo Formation were identified based on integrated analyses of petrographic characteristics, geochemical element analysis and electron back-scattered diffraction of thin sections, including (1) siliceous mudstone, (2) claystone, (3) marlstone, (4) radiolarian-rich mudstone, (5) foraminifera-rich mudstone, and (6) phosphatic mudstone. Geochemical indexes (U/Th, V/(V + Ni), V/Cr, and Ni/Co) indicate that the Madingo Formation on the deep-water slope was characterized by typical oxygen-poor and even anaerobic environment, preserving organic matter and thus preserving sediments with relatively high TOC, abundant marine fossils and framboidal pyrite. The LCB experienced two different marginal marine environments during the deposition of the Madingo Formation. The lower Madingo Formation was characterized by a radiolarian-rich mudstone (the first stage of upwelling) deposited in a marginal semi-restricted sea bay environment (correlated with the Coniacian–Santonian Oceanic Anoxic Event 3; OAE-3), with up to 4.0% TOC, and types II2 and II1 organic matter. The upper Madingo Formation was characterized by foraminifera-rich and phosphatic mudstone (the second stage of upwelling) deposited in a marginal open marine environment (correlated with the Paleocene-Eocene Thermal Maximum; PETM), with up to 4.83% TOC and 5.0 mg/g phosphate that is rich in types I and II1 organic matter. The whole Madingo deposition is estimated to have spanned a 52-Myr period, and the low sediment accumulation rate of approximately 9 μm/yr can lead to a high TOC content. The three identified condensed sections include radiolarian-rich, foraminifera-rich or phosphatic mudstones that deposited in the deep-water slope, were probably marine source rocks for post-salt exploration in West Africa.

Paleostress evolution of the West Africa passive margin: New insights from calcite twinning paleopiezometry in the deeply buried syn-rift TOCA formation (Lower Congo basin)

Accurate characterization of hydrocarbon reservoirs requires a good understanding of the paleostress history of their host sedimentary basin. This study aims at reconstructing the paleoburial and paleostress history of the syn-rift Barremian TOCA Fm. in the Lower Congo basin (West African margin). Two oriented borehole cores drilled offshore Congo were investigated using stress inversion techniques applied to calcite mechanical twins to constrain paleostress orientations and magnitudes. The inversion of calcite twins was performed on a widespread early diagenetic cement (~129 to ~113 Ma) and revealed that the TOCA Fm. has undergone a complex polyphase stress history, including (1) extensional stress regimes with vertical σ1 and horizontal σ3 trending NE-SW and WNW-ESE (N100) associated with the rifting episode preceding the opening of the South Atlantic (130 to 112 Ma), and with mean differential stresses of ~47 MPa for (σ1-σ3) and ~ 20 MPa for (σ2-σ3). The early N100 extension is associated with the development of normal faults striking N-S that likely reactivated inherited basement structures. The direction of extension evolved during the Barremian into the main NE-SW extension marked by the dominant normal faults striking NW-SE. (2) Compressional and strike-slip stress regimes with horizontal σ1 oriented ~N-S possibly related to the far-field intraplate transmission of orogenic stresses generated at the distant Africa-Eurasia plate boundary at ~67–60 Ma, and with mean differential stresses of 40 MPa for (σ1-σ3) and 28 MPa for (σ2-σ3). (3) Compressional and strike-slip stress regimes with horizontal σ1 oriented ENE-WSW to ~E-W that we tentatively relate to the mid-Atlantic ridge push and prevailing since ~15 Ma onwards, associated with mean differential stresses of ~45 MPa for (σ1-σ3) and ~ 18 MPa for (σ2-σ3). Our results reveal that the TOCA Fm. recorded mainly far-field stress effects that could be related to interactions between the African plate and surrounding plates, and that divergent passive margins may experience a complex tectonic history including both extensional and compressional events.

A multiple-point stochastic-based turbidite lobe architecture geomodeling: A case study from L Oilfield, Lower Congo Basin, West Africa

As a prominent component of turbidite deposition systems, turbidite lobe internal architecture characterization has proven essential due to its complicated sedimentary hierarchy and evident heterogeneity. This paper demonstrates an integrated methodology for doing a multiple-point stochastic (MPS) simulation of deepwater turbidite single-lobe architecture. Based on the logging data, high-frequency seismic data, thorough architectural feature analysis, and 3D training image, MPS-based geologic modeling of the Miocene turbidite lobe reservoir in the Lower Congo Basin is carried out. This effort has two objectives: (1) to expand the geologic knowledge base of deepwater turbidite lobes with morphology parameters and (2) to develop a process of turbidite geomodeling that could characterize the architectural hierarchy of a single lobe with limited difficult data. As a first step, we analyze and characterize properties of the single-lobe element characteristics and the manner of sedimentary dispersion using 145 m long cores, well logging, and seismic analysis. Second, shallow seismic-based turbidite lobes pick-up and morphology parameter measurements have been conducted to collect quantitative characteristics of turbidite lobe and will be used as geomodeling guidance. Third, a 3D lobe complex training image with single-lobe architecture elements superposition is derived by a seismic geobody caving (using threshold truncation) and enhanced based on the sedimentary distribution mode. An MPS simulation incorporating well data, morphological parameters, training image, and seismic inversion constraint is then performed, which results in obtaining an architecture model that could describe a single lobe. The simulation results generally followed the lobe architecture elements morphology and superposition. The coincidence between the MPS simulated turbidites lobe complex architecture model and the posterior well could reach up to 86%. The paper gives the methodology for a case study that proved the implementation of single turbidite lobe architectural characterization using an MPS, and the recommended process could be applied to other fields.

Depicting past stress history at passive margins: A combination of calcite twinning and stylolite roughness paleopiezometry in supra-salt Sendji deep carbonates, Lower Congo Basin, west Africa

The paleostress history and associated deformation mechanisms affecting passive margins are seldom studied, as access to offshore parts is rather limited. We analyze an offshore wellbore core of the Albian, post-rift carbonates of the Sendji Fm which directly overlies the salt of the Aptian Loeme Fm in the Lower Congo Basin. Paleopiezometry based on stylolite roughness inversion (SRIT) and calcite twin inversion (CSIT) was combined with fracture analysis, U–Pb geochronology of calcite cement and burial modeling to unravel the orientations and magnitudes of horizontal and vertical stresses affecting the Sendji Fm over time, with a focus on the impact of salt tectonics on stress records. The results of SRIT on bedding-parallel stylolites constrain the range of depths over which the Sendji Fm strata deformed under a vertical principal stress σ1 to 650–2800 m (median ∼1300 m). Once projected onto the burial model derived from TemisFlow™ software, the range of depths converts to a period of pressure solution activity, from 101 to 15 Ma. Calcite twin measurements within the early diagenetic cement (U–Pb age = 101 ± 1 Ma) reveal three main types of stress regimes: (1) extensional stress regimes with σ3 trending ∼ N–S and ∼E-W associated with local, thin-skinned salt tectonics (101–80 Ma), (2) strike-slip stress regimes with σ1 trending ∼ NW-SE to NNE-SSW and a compressional stress regime with σ1 trending NNW-SSE, reflecting possible intraplate stress transfer from the distant Africa-Eurasia plate boundary (67–60 Ma); (3) a strike-slip and a compressional stress regime with σ1 trending E-W likely related to the mid-Atlantic ridge push possibly combined with effects of variations in elevation and density of the lithosphere and sedimentary flexural loading (15 Ma to present). The paleostress sequence suggests that the sedimentary cover was decoupled from the crust during salt tectonics and then recoupled from the late Cretaceous onwards.

Recognition and Prediction of Source Rocks of the Madingo Formation in the Lower Congo Basin

Recognition and Prediction of Source Rocks of the Madingo Formation in the Lower Congo Basin

Disentangling the Diversity of the Labeobarbus Taxa (Cypriniformes: Cyprinidae) from the Epulu Basin (DR Congo, Africa)

In an attempt to disentangle the complex taxonomy of the Labeobarbus species of the Epulu River, a right bank headwater affluent of the Aruwimi, Central Congo basin, a morphological study was undertaken on 221 specimens from the Epulu and 32 type specimens. As a result, five different species have been distinguished, including four so-called rubberlips, L. caudovittatus, L. macroceps, L. mawambiensis, and L. sp. ‘thick lip’, and one chiselmouth, L. longidorsalis. While rubberlips have a curved mouth with well-developed lips and often a mental lobe, chiselmouths have a straight mouth with a keratinised cutting edge on the lower jaw. Among the specimens examined, several presented an intermediate mouth morphology between L. mawambiensis and L. longidorsalis, either with one or two pairs of barbels. One specimen exhibited an intermediate morphology between L. mawambiensis and L. macroceps. This morphological study, complemented with a molecular study of the mitochondrial gene cytochrome b (cyt b), suggests that these intermediates are probably hybrid specimens. The Epulu case is reminiscent to a case of possible hybridisation recently discovered in the Inkisi River (Lower Congo basin), but differs in having a lower relative abundance of hybrid specimens in the population, and in phylogenetic patterns.

Multi-proxy reconstruction of the burial history and porosity evolution of the TOCA carbonate formation in the Lower Congo basin (South West Africa)

The timing of porosity destruction in reservoir rock is key for hydrocarbon exploration. This study constrains the porosity destruction of the syn-rift Barremian (130-125 Ma) TOCA Fm. from one drill core located in the Lower Congo basin (West African passive margin). We apply an unprecedented multi-proxy approach to reconstruct the absolute timing of mechanical compaction, pressure-solution and cementation as well as their relative contribution to porosity destruction. LA-ICP-MS U–Pb geochronology combined with petrological observations suggest that the main interstitial diagenetic cement C1 filling the porosity of the packstones and dated 127.4 ± 2.2 to 119.4 ± 6.4 Ma predates pressure-solution. The quantification of the cement distribution by image analysis indicates that C1 clogged ∼30% of the initial porosity before the strata were buried at 400 m. We assume that the early cementation limited the effect of mechanical compaction on porosity reduction which is estimated to ∼2% in the first 100 m of burial. In contrast, a first order estimate of the chemical compaction-reprecipitation can account for up to ∼6% of the initial porosity destruction, as estimated by the inversion of sedimentary stylolite roughness. This technique also documents that the burial-related pressure-solution in the TOCA Fm. occurred in the 550–1750 m burial depth range corresponding to a time spanning from 117 to 95 Ma considering the burial-time model of the TOCA Fm. Our study reveals that the initial porosity of carbonates was reduced down to its current value of 4–8% within the first 35 Ma of its burial history, reaching ∼10% after only 10 Ma, i.e. in the first 400–500 m of burial. This case study indicates that the fate of reservoir properties in bioclastic carbonate formations such as the TOCA Fm. may be largely controlled by early, very shallow diagenetic processes rather than subsequent deep-burial mesogenetic reactions.

Gas Profiles Unravel Fractured and Compartmentalized Reservoirs

The profiles of gas in reservoirs of the Nene Oil Field in the Lower Congo Basin was modelled and evaluated for the objective of delineating the reservoir structure. The wells are NNM Well 6, NNM Well 301 and NNM Well 302. The C1 profiles show significant difference between wells 6 and 301 relative to well 302. The C1 profile for Well 302 unravels gas migrations from different compartments at the reservoir depth and mixes at a depth of 1.5KM. The observation also indicates the presence of a fracture that allow homogenization of the gases at that depth. The iC4/nC4 ratio for NNM Well 302 showed a profile for which the ratio is greater than 1.0 throughout the well section downdip. The observation portrays biodegradation throughout the well section generation from an immature source. The study shows that the NNM Well 6 reservoir is laterally compartmentalized from others, while all the well shoe some potential for vertical continuity of the wells

The Late Cretaceous—Miocene supra‐salt structures in Block M, Lower Congo Basin (Congo, West Africa) and the controls on channel development

The Lower Congo Basin is a typical passive continental margin basin of West Africa and is currently the focus and hot spot of deep‐sea oil and gas exploration. Previous studies have focused on the deformation process and mechanism of the salt rock itself, but have ignored the interaction process between the faults and salt diapirs. The direct influence of the interaction process between the faults and salt diapirs on oil and gas exploration is reflected in the control of the reservoir distribution. In recent years, most of the oil and gas discovered in the Lower Congo Basin have been concentrated in the Oligocene–Miocene turbidite reservoirs, and the distribution of channel sand bodies is largely affected by supra‐salt tectonic activity. In this study, Block M in the Lower Congo Basin was selected for study. Based on the 3D seismic, drilling, and logging data, the typical structural styles and stress mechanisms were analysed. The 2D Move software was used to restore the tectonic evolution history and, based on this, established the interaction model of salt diapirs and faults, and summarized the action modes of diverse types of sedimentary channels. The research results are expected to lay the foundation for follow‐up studies on the laws of hydrocarbon accumulation.

Molecular footprint of parasite co-introduction with Nile tilapia in the Congo Basin

Nile tilapia, one of the most popular aquaculture species worldwide, has been introduced into the Congo Basin several times for aquaculture purposes. Previous studies based on morphological features showed that some of the monogenean gill parasites were co-introduced with Nile tilapia and some spilled over to native Congolese cichlids. In this study, we genetically investigated the co-introduced monogeneans of Nile tilapia from three major parts of the Congo Basin: Upper, Middle and Lower Congo. We sequenced 214 specimens belonging to 16 species of Monogenea, collected from native and introduced tilapia species from Congo, Madagascar and Burundi. We evaluate their position in a phylogeny including 38 monogenean species in total. Our results confirm the co-introductions in the Congo Basin and suggest one unreported parasite transmission from introduced Nile tilapia to native Mweru tilapia in Upper Congo, which was undetectable with a morphological study alone. Shared parasite COI haplotypes between Madagascar and the Congo Basin illustrate how anthropogenic introduction events homogenize parasite communities across large geographical distances and thereby disrupt isolation by distance patterns. Contrary to our expectation, the parasite populations co-introduced in the Congo Basin reveal a high COI diversity, probably resulting from multiple Nile tilapia introductions from different geographic origins. Additionally, we tested the barcoding gap and the performance of mitochondrial COI and nuclear ribosomal ITS-1, 28S and 18S markers. We found a significant barcoding gap of 15% for COI, but none for the other markers. Our molecular results reveal that Cichlidogyrus halli, C. papernastrema, C. tiberianus, C. cirratus and C. zambezensis are in need of taxonomic revision.

Three Odes in G#

Three Odes in G# Jeremy Jacob Peretz (bio) Everyday/Unspeakable/Ethics Red slaves (native-Americans) are used only for domestic work in Surinam because they are too weak to work in the fields. Negroes are thus needed for fieldwork. The difficulties in this case are not the result of a lack of coercive measures, but the natives in this part of the world lack ability and durability. —Immanuel Kant, "Von der verschiedenen Racen der Menschen" ["Of the Different Human Races"] The white is opposed to the red, while the black disappears from the picture. —Anita Jacobson-Widding, Red—White—Black as a Mode of Thought: A Study of Triadic Classification by Colours in the Ritual Symbolism and Cognitive Thought of the Peoples of the Lower Congo Everyday life, which is the backdrop, the hum, the private, and the quotidian of civil society, can only cohere by way of the imaginative labor which genocided and banished the object it constructed as "Savage" to the reservations of White ethics and by way of a simultaneous imaginative labor that keeps the gratuity of Black genital accumulation and destruction from occurring between White legs. —Frank B. Wilderson III, Red, White, and Black: Cinema and the Structure of U.S. Antagonisms Exxon Exxoff Mobilizetalk ground and doact flow like vinyasalike Mother's bloodthrough a pipelinea wave moving anoffshore rig like a [End Page 88] torrent from deepin the continent—from the Amazonstrong to knockthe mightiest drillswith force that somecorrupt parking meterscheme couldn't everimagine to rewriteA Projected Memory of theGuyanese Working Peopleas if born in the realitiesof Octavia Butler'sBacon's Rebellion—and the settlers demanddeath extracted offto the next moonMars or Venus' bodies,or relayed circuitouslysapping and sopping offall those many Others,sipping Coca-Cola orside-stepping a War onTerror/Drugs life/cokewhile others still prefermauby or coconut waterknowing patterns that havecome to make mined skyfruit and flesh morselized [End Page 89] into common comestiblesmust be a philosophy thatcannot be unquestionable. [End Page 90] Mixed(down) Methods(man) for Charlene Wilkinson Groundings over lands and seaTanzania (troubling Nyerere)To the UWI to UG (and Fatman)From Oriental and African Studies,UCLA too. What they did to you! Brother WalterYou take A View from beyondThe grave of The Third WorldAt the babylonian enterprise'sIsms & Schisms, says ProphetBob, at the Russian Revolution,Wreckage triangulating flowsOf force—coloniality of powerDrifting carbon-chain islandsMushroomed and myceliatedDirt rhizomated web-worksUndermining barriers andBoundaries, borders of bodiesLike vessels tipped just soTo release a precious fumeOf spirit to the still-presentDeparted sitting with us—Grounding. Cane-cuttersAnd Rastafari (when thatHere still was a dirty word, a [End Page 91] Dutty being/nonpersonthing)All men too, no auntie/anti-man,Among the partisan jumbi-scapesOf the Uptown World crisscrossingThe Dungles of UnderdevelopmentWith nerves jolting veins, necksNext necks, knees, rods clubsCutlass, Rod-knees and necksOf Black people who are BlackIn response to the call of Capital,That wild white-noise of burden,Black because we are not whiteIn this Land of Many Waters theEarth-over under sun and moon us"Recognisably African or Indian,"Or Dougla—with a split-neck caste,Stabilizing bodies' politicks with plaster (of Paris?)That's hardened heavy as if immoveable. I been in Camp Street, too,Like Brother Walter before.Rodded and trotted and kneed.Incient motioned to his shrineOf present tense memory, andThen I's able to catch myself.Outside just down HadfieldWhere he watched me onMy first date with who'dBecome my child's mother, [End Page 92] And put it in my heart to live,When I sighted Walter, and IRemembered—Oh, in LifeYou Do Good, and/not stupidness,Not 'cause you're looking like aY-T with a privilege pass of color/ismWhitey Red-Ras who brung AIDSSugar and slavery you must act soWith your...

Riverscape genomics of cichlid fishes in the lower Congo: Uncovering mechanisms of diversification in an extreme hydrological regime.

Freshwater fishes are notably diverse, given that freshwater habitat represents a tiny fraction of the earth's surface, but the mechanisms generating this diversity remain poorly understood. Rivers provide excellent models to understand how freshwater diversity is generated and maintained across heterogeneous habitats. In particular, the lower Congo River (LCR) consists of a dynamic hydroscape exhibiting extraordinary aquatic biodiversity, endemicity, morphological and ecological specialization. Previous studies have suggested that the numerous high-energy rapids throughout the LCR form physical barriers to gene flow, thus facilitating diversification and speciation, generating ichthyofaunal diversity. However, this hypothesis has not been fully explored using genome-wide SNPs for fish species distributed across the LCR. Here, we examined four lamprologine cichlids endemic to the LCR that are distributed along the river without range overlap. Using genome-wide SNP data, we tested the hypotheses that high-energy rapids serve as physical barriers to gene flow that generate genetic divergence at interspecific and intraspecific levels, and that gene flow occurs primarily in a downstream direction. Our results are consistent with the prediction that powerful rapids sometimes act as a barrier to gene flow but also suggest that, at certain temporal and spatial scales, they may provide multidirectional dispersal opportunities for riverine rheophilic cichlid fishes. These results highlight the complexity of diversification processes in rivers and the importance of assessing such processes across different riverscapes.

Climate-driven dinoflagellate cyst stratigraphy of the Oligocene-lower Miocene turbidite succession of the Lower Congo Basin (offshore NW Angola)

Biostratigraphic studies of cuttings from wells located in the Lower Congo Basin, offshore northwestern Angola, document with unprecedented wealth of data the organic-walled dinoflagellate cyst (dinocyst) assemblages of the Malembo Formation. The identification of a series of dinocyst events (highest and lowest occurrences, influxes and acmes) recurring in the same stratigraphic position in different wells and cross-calibrated by calcareous nannofossil data, provides a tool for age control and correlation of the Oligocene and lower Miocene in the equatorial and South Atlantic region.Proceeding downwards in the stratigraphy of the examined succession, the lowest occurrence of Pyxidinopsis pastilliformis, detected within the CN3 nannofossil Zone, approximates the Langhian-Burdigalian boundary, whereas the lowest occurrences of Sumatradinuim druggii and Sumatradinium hispidum occur at the base of the CN2 nannofossil Zone in the Burdigalian. The lowest occurrences of Sumatradinium soucouyantiae and Barssidinium taxandrianum fall within the Zone of acme of Hystrichokolpoma rigaudiae at the Burdigalian-Aquitanian transition, and immediately above the acmes of Cribroperidinium tenuitabulatum and Systematophora-Cleistosphaeridium group that are supposed to reflect climate cooling pulse Mi-1a. The presence of Chiropteridium spp. and Membranophoridium aspinatum is limited to the upper part of the Chattian. An influx of Tuberculodinium vancampoae, possibly related to a warmer interlude during a period of overall climate cooling, occurs in proximity of the Chattian-Rupelian boundary. The nearly synchronous highest occurrences of Gerdiocysta conopeum, Eocladopyxis peniculata and Heterosphaeridium sp. provide a robust infra-Rupelian biohorizon. Further down in the Rupelian, the influxes of Pentadinium laticinctutm and Distatodinium paradoxum are interpreted as responses to cooling pulses. The lowest occurrence of G. conopeum, detected in the basal part of the NP23 nannofossil Zone, corresponds to the global first appearance of this excellent Rupelian marker. Genera Deflandrea and Wetzeliella are noticeably missing in the studied material just as they lack in some coeval dinocyst assemblages reported in the literature from low paleolatitude Atlantic sections.The recorded alternation of influxes and acmes of Gonyaulacoid dinocyst taxa indicative of cooler and warmer water conditions was probably climate-driven, i.e. paced by cooling pulses and relatively warmer interludes characterizing the climate evolution during the Oligocene and early Miocene. Indeed, the lack of acmes of Peridinioid cysts suggests that climate, rather than constantly elevated nutrient levels ensured by the Congo River discharge, was the discriminant factor triggering the observed blooms of Gonyaulacoid cyst-forming taxa.The delivery of large volumes of sands into deepwater settings via gravity-driven fluxes was favored by sea-level drops and is ultimately associated with pulses of climate cooling and Antarctic ice-sheet growth, finally reflected by the composition of the dinocyst assemblages. In addition to paleoecological factors, hydraulic fractionation resulting from sedimentary processes that transported palynomorphs down the slope as part of turbidite fluxes, contributed to shape the palynological assemblages observed in this study.

Riverscape genomics of cichlid fishes in the lower Congo: Uncovering mechanisms of diversification in an extreme hydrological regime

Riverscape genomics of cichlid fishes in the lower Congo: Uncovering mechanisms of diversification in an extreme hydrological regime

Exhumation of the passive margin of the DR Congo during pre- and post- Gondwana breakup: Evidence from low-temperature thermochronology, geology and geomorphology

The Lower Congo region encompasses the South Atlantic passive margin of the Democratic Republic of Congo (Central Africa). It is host to the lowermost course of the Congo River, cutting through the Central African Atlantic Swell (CAAS). The region is underlain by litho-structural units of the Pan-African West Congo Belt, which consists of different tectono-metamorphic domains. The Precambrian basement is covered to the west by marine deposits of the South Atlantic Ocean and to the east by continental deposits of the Congo Basin. In this study we aim to constrain the timing of uplift and exhumation of the CAAS by using apatite fission track (AFT) thermochronology in combination with an updated overview of the geology and geomorphology of the Lower Congo region. AFT ages vary widely between 108 and 312 Ma. Short track lengths (11–12 μm) and broad, complex track length distributions indicate mixed ages between multiple thermal events. We derive the timing of exhumation from inverse thermal history models, that show that the Lower Congo region experienced a first exhumation event before Gondwana breakup during the Carboniferous to Middle Jurassic. This event is probably related to compressive forces at the boundaries of Gondwana. Both rifting and subsequent opening of the South Atlantic Ocean do not seem to have had a pronounced effect on the CAAS region. During the Late Cretaceous to Palaeogene, a slight reheating is suggested and could be due to subsidence and consequential modest reburial of the Lower Congo rocks. A second phase of exhumation initiated around the Palaeogene–Neogene and eventually emplaced the sampled rocks at surface temperatures. The multi-phased differential denudation results from reactivation of fault-bounded tectono-metamorphic blocks of the Precambrian basement, controlled by the combination of two systems of faults related to the Cretaceous South Atlantic Ocean opening and Pan-African orogeny respectively. Differential denudation of the Lower Congo region is also well-marked by independent qualitative indicators of the present-day geomorphology including distinct knickpoints and steep valleys along the course of the Lower Congo River, reworking of erosion surfaces and associated laterite crust and contrasting karst morphology.