Permian-Triassic palaeoclimatic cycles of the Karoo Supergroup in Mozambique, and its implications on a changing world

Funder

Organizational Unit

Publications

Permian stratigraphy and palynology of the Lower Karoo Group in Mozambique: a 2020 perspective

Publication . Lopes, Gilda; Pereira, Zélia; Fernandes, Paulo; Marques, João; Mendes, Márcia; Götz, Annette E.

ABSTRACT: In the past decade, the increase in the number of palynological works in Mozambique documents the significance of palynology in dating the late Palaeozoic basins in this region of southwestern Gondwana. The new information gained mainly from the study of the Moatize-Minj ova Coal Basin is the basis for a better understanding of the regional biostratigraphy, as well as of palaeoenvironmental and palaeoclimatic conditions during the Permian. Here we provide a review on the Permian palynostratigraphy and its implications for lithostratigraphic correlation of Lower Karoo basins in Mozambique. The new biostratigraphic information leads to the conclusion that an age update for the lithostratigraphic units established for the Lower Karoo in Mozambique (Virzi, Moatize, and Matinde formations) is most needed. The Cisuralian palynological association in Mozambique is characterized by long-range taxa recorded since the middle Cisuralian (Sakmarian to Artinskian) (Alisporites spp., Cannanoropollis spp., Horriditriletes spp., Laevigatosporites spp., Potonieisporites spp., Protohaploxypinus spp.). Several first occurrences are also recorded in the late Cisuralian (Kungurian) (e. g., Cirratriradites africanensis, Marsupipollenites triradiatus, and Vittatina spp.). The Guadalupian association is mainly characterized by taxa that extend their range since the Cisuralian (e. g., Alisporites spp., Cirratriradites africanensis, Guttulapollenites hannonicus, Horriditriletes ramosus, Kraeuselisporites enormis, Lueckisporites virkkiae, Limitisporites monstruosus, Marsupipollenites striatus, M. triradiatus, Pakhapites fusus, Platysaccus papilionis, Thymospora pseudothiessenii, and Weylandites lucifer), with only few first occurrences (Lueckisporites virkkiae, Striatopodocarpites cancellatus, and S. fusus) and last occurrences (Cirratriradites africanensis, Limitisporites monstruosos) being recorded. The Lopingian palynological association includes most of the taxa described for the Guadalupian. In contrast, Corisaccites alutas, Indotriradites niger, Klausipollenites schaubergeri, Lunatisporites pellucidus, Osmundacidites senectus, Polypodiisporites spp., P. mutabilis, and Protohaploxypinus microcorpus are recorded for the first time. Indication of the proximity to the Permian-Triassic Boundary is supported by the occurrence of Klausipollenites schaubergeri, Protohaploxypinus microcorpus, and Osmundacidites senectus in the upper part of the Matinde Formation. Based on the palynological data, the oldest rock unit, the Virzi Formation, was deposited in the Permian (middle Cisuralian), and no older sedimentary rocks are currently known for the Lower Karoo Group in Mozambique. The palynological associations described also indicate that the Authors' deposition of the Moatize Formation occurred from the middle Cisuralian to the latest Guadalupian/early Lopingian, whilst the deposition of the Matinde Formation lasted from the late Guadalupian to the latest Lopingian. Thus, the boundary between both formations is assumed to be diachronous.

2021-01Journal article

Open access

First record of Permo-Triassic palynomorphs of the N'Condédzi sub-basin, Moatize-Minjova Coal Basin, Karoo Supergroup, Mozambique

Publication . Galasso, Francesca; Pereira, Zélia; Fernandes, Paulo; Spina, Amália; Marques, João

ABSTRACT: ermian-Triassic ages have been identified for the first time in the Karoo Supergroup of the N'Condedzi sub-basin, Moatize-Minjova Coal Basin, Mozambique. This transition was identified in a coal exploration borehole that penetrated the Matinde and Cadzi formations. The top of the Matinde Formation is dated latest Permian (Lopingian), and the Cadzi Formation is attributed to Triassic based on palynostratigraphy. The Lopingian age is established by the identification of three palyno-assemblages: Assemblage L1 based on the first occurrence (FO) of Guttulapollenites pollen, Assemblage L2 is marked by the FO of Thymospora pseudothiessenii, and Assemblage L3 is defined by the FO of Osmundacidites senectus. Triassic palynomorphs were identified for the first time in Mozambique (Karoo basins). The data allowed the identification of three assemblages: Assemblage T1 defined by the FO of Densoisporites nejburgii of Induan age, Assemblage T2 is marked by the FO of Platysaccus queenslandi and assigned to the Olenekian age, and Assemblage T3 is defined by the FO of Samaropollenites speciosus and Enzonalasporites vigens, indicating a Carnian age. No Middle Triassic rocks were identified, and the early Triassic sediments are overlain by sedimentary rocks of Carnian age, a hiatus that may correspond to an important tectonic event with uplift and erosion. This tectonic event is also suggested by the occurrence of common reworked Permian palynomorphs in the Carnian sedimentary rocks. These new data constrain the age of the Karoo Supergroup formations of Mozambique and contribute to improve the palaeoecological, palaeoclimatic evolution, and the palaeogeographic position of the Karoo Mozambique basins within the Gondwana supercontinent.

2019Journal article

Open access

Palynology of the Muarádzi sub-basin, Moatize-Minjova Coal Basin, Karoo Supergroup, Mozambique

Publication . Pereira, Zélia; Fernandes, Paulo; Lopes, Gilda; Marques, João; Vaz, Maria; Costa, Marta; Correia, João; Castro, Lígia; Galasso, Francesca

ABSTRACT: The detailed palynostratigraphic study of four boreholes in theMuarádzi sub-basin,Moatize-Minjova Coal Basin (MMCB) southeast of Moatize, allowed the assignment of relative ages to the stratigraphic units. Three assemblages were studied in detail and are assigned to the Lopingian. Assemblage L1 is characterized by the rich occurrence of Guttulapollenites and Weylandites. Assemblage L2 is defined on the first occurrence (FO) of abundant Thymospora pseudothiessenii together with Indotriradites niger, kraeuselisporites spp., Polypodiisporites mutabilis and Polypodiidites sp. Assemblage L3 is characterized by the first occurrence of Osmundacidites senectus together with the taxa described from the previous assemblages. Palynological correlation with other Karoo basins is discussed and three distinct palynostratigraphic events emerge based on the FO and abundance of key taxa (as for instance, FO of G. hannonicus, T. pseudothiensenii and O. senectus). A close palynological correlation between Mozambique (Moatize-Minjova Basin), Tanzania (Selous Basin), Zambia (mid-Zambezi Basin) and Madagascar palynoevents is established. This major region can be assigned to the northern Karoo-aged basins of southcentral Africa and the palynoevents can be correlated with Lopingian assemblages of Pakistan, India and some basins of East Antarctica. The southern Karoo-aged basins of south-central Africa, including South Africa and Zimbabwe, show different Lopingian palynoevents and a direct correlation is demanding. These palynological datamay open newperspectives for coal exploration in theMMCB as the coal deposits showawider stratigraphic distribution, reaching until the latest Lopingian.

2019Journal article

Open access

Thermal history and basin evolution of the Moatize - Minjova Coal Basin (N'Condédzi sub-basin, Mozambique) constrained by organic maturation levels

Publication . Galasso, Francesca; Fernandes, Paulo; Montesi, Giovanni; Marques, João; Spina, Amália; Pereira, Zélia

ABSTRACT: Kerogen concentrates obtained from Lopingian (Late Permian) to Upper Triassic mudrock lithologies of seven coal exploration boreholes, drilled in the Moatize – Minjova Coal Basin (N'Condédzi sub-basin, Mozambique), were studied by means of vitrinite reflectance (VR), spore fluorescence and spore colour, in order to constrain the thermal history and basin evolution by organic maturation levels. VR increases with depth, indicating organic maturation related to sediment burial for most of the boreholes. Modelled VR data indicate a regional palaeogeothermal gradient between 35 and 40 °C/km. Lower Jurassic doleritic intrusions observed in three boreholes had only local thermal effects without affecting the regional palaeogeothermal gradient. Two boreholes located near the basin margin show high palaeogeothermal gradients suggesting thermal processes other than heating due to burial were involved. These processes may have involved hot diagenetic fluids circulating through fault zones and/or permeable lithologies, locally elevating geothermal gradients. Circulation of these fluids was induced by lithostatic pressure due to rapid rates of sedimentation. These high sedimentation rates lead to the accumulation of a thick succession (over 2000 m) of Lopingian (Late Permian) to Upper Triassic siliciclastic sediments. All the organic maturation indices measured and the age of the successions indicate that organic maturation occurred during or after Late Triassic times. However, the presence of reworked Permian palynomorphs into Upper Triassic sediments and the absence of Middle Triassic sediments indicate an exhumation and erosion of Permian strata in Middle Triassic times. The organic maturation levels of the reworked palynomorph population are considerably higher than the indigenous Upper Triassic population, indicating that they attained higher burial temperatures prior to being reworked.

2019Journal article

Open access

Late Permian palaeoenvironmental evolution of the Matinde Formation in the Muarádzi Sub-basin, Moatize-Minjova Basin, Mozambique

Publication . Lopes, Gilda; Pereira, Zélia; Fernandes, Paulo; Mendes, Márcia; Marques, João; Jorge, Raul CG Santos

ABSTRACT:A multidisciplinary study involving lithofacies analysis, palynofacies, and palynology is presented for the Muaradzi Sub-basin. This sub-basin is part of the Moatize-Minjova Basin (MMB), an important Karoo aged coalfield in Mozambique. A total of 99 core samples from 3 coal exploration boreholes (DW11, DW21, and DW141) were analysed and all the successions were assigned a Lopingian age based on palynology. According to the data, in the Muar ' adzi Sub-basin, a vast lowland fluvial setting existed with floodplains and wetlands, in an area controlled by tectonic movements associated with a continental rifting phase. Typical vegetation of the Glossopteris Province is recorded in the palynological assemblages of this sub-basin, which allowed for the characterization of a flora dominated by glossopterids (Protohaploxypinus and Striatopodocarpites) and gymnosperm pollen (Alisporites). Other palynomorphs revealed the presence of gingkoales, ferns (Filicopsida), sphenopsids, and lycopsids in the area, indicating a typical lowland setting. Humid and warm climates, associated with higher CO2 atmospheric levels, promoted the growth of widespread vegetation that led to the development of the thick coal beds in anoxic to dysoxic depositional environments.

2021-04Journal article

Open access