scholarly journals A tectonic carpet of Variscan flysch at the base of an unrooted accretion prism in NW Iberia: U-Pb zircon age constrains from sediments and volcanic olistoliths

2020 ◽  
Author(s):  
Emilio González Clavijo ◽  
Ícaro Dias da Silva ◽  
José R. Martínez Catalán ◽  
Juan Gómez Barreiro ◽  
Gabriel Gutíerrez Alonso ◽  
...  
Keyword(s):  
General Structure ◽  
Source Area ◽  
Accretionary Prism ◽  
Upper Ordovician ◽  
Stratigraphic Sequence ◽  
Zircon Age ◽  
Upper Cambrian ◽  
Provenance Areas ◽  
Nw Iberia ◽  
Thrust Sheets

Abstract. The allochthonous complexes of Galicia – Trás-os-Montes Zone (NW Iberia) are part of the tectonic stack that unrooted the Variscan accretionary prism. They are formed by individual tectonic slices marked by specific tectono-metamorphic evolution, which was piled up in a piggy-back thrust complex onto its relative autochthon, the Central Iberian Zone (CIZ). Consequently, allochthony decreases towards lower, more external and younger thrust sheets. The lowermost unit of this pile of slivers is known as Schistose Domain or Parautochthon and bears low metamorphic grade, contrasting with the higher temperatures and pressures estimated for the upper allochthonous units, but sharing the stratigraphic sequence with the underlying autochthon. The Parautochthon is divided in two structural and stratigraphic sub-units: (i) the Lower (LPa) made of synorogenic flysch-type sediments with varied turbiditic units and olistostrome bodies, showing Upper Devonian-lower Carboniferous age on base of the youngest zircon populations and fossiliferous content; (ii) the Upper (UPa), composed of highly deformed pre-orogenic upper Cambrian-Silurian volcano-sedimentary sequence comparable with both the nearby autochthon and the HP-LT Lower Allochthon, laying structurally above. The UPa thrusted onto the LPa by the the Main-Trás-os-Montes Thrust; and the LPa detached from the CIZ relative autochthon by a regional structure (Basal Lower Parautochthon Detachment) which follows the favourable Silurian carbonaceous beds. A review on the detrital zircon studies of the synorogenic LPa complemented by 17 new samples geochronology is here presented. The results support the extension of the LPa underneath the NW Iberia allochthonous complexes, from Cabo Ortegal, to Bragança and Morais Massifs. Its current exposure follows the lowermost tectonic boundary between the Galicia – Trás-os-Montes (allochthon) and Central Iberian (autochthon) Zones. Youngest zircon age populations point to a maximum sedimentation age for the LPa formations ranging from Famennian to Serpukhovian and endorse the piggy-back evolution inside this unit, mimicking the general structure of the Galicia – Trás-os-Montes Zone. The zircon populations in the LPa allow constraining the sedimentary provenance areas, showing the intervention of nearby sources (mostly the UPa) and/or multiply recycled/long transport sediments with typically N-Central Gondwana age fingerprint, also found in the Lower Allochthon, UPa and Autochthon. Complementary geochronology of volcanic olistoliths trapped in the LPa sediments and of upper Cambrian to Upper Ordovician rhyolites from the UPa is also presented, showing a direct relation between the major block's source area (UPa) and the setting place (LPa). Old zircon age patterns show that the LPa sedimentary rocks were recycled from detrital rocks of the allochthon (advancing wedge) and the nearby autochthon (peripheral bulge).

scholarly journals A tectonic carpet of Variscan flysch at the base of a rootless accretionary prism in northwestern Iberia: U–Pb zircon age constrains from sediments and volcanic olistoliths

Solid Earth ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 835-867
Author(s):  
Emilio González Clavijo ◽  
Ícaro Dias da Silva ◽  
José R. Martínez Catalán ◽  
Juan Gómez Barreiro ◽  
Gabriel Gutiérrez-Alonso ◽  
...  
Keyword(s):  
Regional Scale ◽  
Source Area ◽  
Accretionary Prism ◽  
Upper Ordovician ◽  
Stratigraphic Sequence ◽  
Zircon Age ◽  
Provenance Areas ◽  
Thrust Sheets ◽  
Age Patterns ◽  
Tectonic Boundary

Abstract. The allochthonous complexes of Galicia–Trás-os-Montes Zone (NW Iberia) are part of a rootless tectonic stack which preserves part of a Variscan accretionary prism. They are formed by individual tectonic slices marked by specific tectonometamorphic evolutions, which were piled up in a piggy-back mode onto its relative autochthon, the Central Iberian Zone (CIZ). Allochthony decreases from the structurally upper thrust sheets towards the lower ones. The lowermost unit of the stack is known as the Parautochthon or Schistose Domain. It is characterized by a low metamorphic grade in contrast with higher temperatures and/or pressures estimated for the overlying allochthonous units and shares the stratigraphic sequence with the underlying autochthon. The Parautochthon is divided in two structural and stratigraphic sub-units: (i) the Lower Parautochthon (LPa) is made of synorogenic flysch-type sediments with varied turbiditic units and olistostrome bodies, showing Upper Devonian–lower Carboniferous age according to the youngest zircon populations and fossiliferous content; (ii) the Upper Parautochthon (UPa) is composed of highly deformed preorogenic upper Cambrian–Silurian volcano-sedimentary sequence comparable with the nearby autochthon and to some extent, also with the high-P and low-T Lower Allochthon laying structurally above. The UPa was emplaced onto the LPa along the Main-Trás-os-Montes Thrust, and the LPa became detached from the CIZ relative autochthon by a regional-scale structure, the Basal Lower Parautochthon Detachment, which follows a weak horizon of Silurian carbonaceous slates. A review on the detrital zircon studies on the synorogenic LPa complemented by zircon dating of 17 new samples is presented here. The results support the extension of the LPa underneath the NW Iberian allochthonous complexes, from Cabo Ortegal, to Bragança and Morais massifs. Its current exposure follows the lowermost tectonic boundary between the Galicia–Trás-os-Montes (allochthon) and Central Iberian (autochthon) zones. The youngest zircon age populations point to a maximum sedimentation age for the LPa formations ranging from Famennian to Serpukhovian and supports the piggy-back mode of emplacement of the Galicia–Trás-os-Montes Zone, of which it represents the latest imbricate. The zircon age populations in the LPa allow the sedimentary provenance areas to be constrained, showing the intervention of nearby sources (mostly the UPa) and/or multiply recycled and long-transport sediments with a typically north-central Gondwana age fingerprint, also found in the Lower Allochthon, UPa and Autochthon. Complementary geochronology of volcanic olistoliths trapped in the LPa sediments and of late Cambrian to Upper Ordovician rhyolites from the UPa is also presented. It shows a direct relationship between the major blocks source area (UPa) and the setting place (LPa). Old zircon age patterns show that the LPa sedimentary rocks were recycled from detrital rocks of the allochthon (advancing wedge) and the nearby autochthon (peripheral bulge).

scholarly journals Archaeopetrological approximation to the lithic procurement of the neolithic axes and adzes from Can Sadurní’s cave (Begues, NE Iberian Peninsula)

2016 ◽  
Vol 3 (2) ◽  
Author(s):  
Mar Rey-Solé ◽  
Gemma Alías ◽  
Mireia Ache ◽  
Elicinia Fierro ◽  
Manel Edo ◽  
...  
Keyword(s):  
Iberian Peninsula ◽  
Raw Materials ◽  
Source Area ◽  
Archaeological Site ◽  
Igneous Rocks ◽  
Contact Aureole ◽  
Stratigraphic Sequence ◽  
Materials Used ◽  
Granodiorite Porphyry ◽  
Ne Iberian Peninsula

Can Sadurní’s cave, located in Begues (NE Iberian Peninsula), in the Baix Llobregat region, is an archaeological site with a wide stratigraphic sequence covering from the Epipaleolithic hunter-gatherers societies at the beginning of the Holocene to Roman times. During the excavations of the last years a large number of different raw materials used for the manufacture of axes have been recovered.The present study is focused on the Neolithic sequence. 31 axes and adzes have been characterised petrographically with the aid of a binocular microscope and transmission microscope. A great variety of rocks constitute the raw materials of these stone tools, ranging from contact and regional metamorphic rocks to plutonic and porphyric igneous rocks. The formers are the most abundant (up to 78%) and include hornfels, spotted phyllites, marbles, quartzites, slates and phyllites. The igneous rocks consist of granodiorite, porphyry and aplites. Such a great assemblage of rocks matches in a geological context representative of a plutonic intrusion and its metamorphic contact aureole. Following that scenario we suggest that the most likely source area for all these materials occur at the Collserola hills, at 27 km far to the east from the cave, at the other side of the Llobregat River, where an Hercynian granodiorite and related igneous rocks intruding Ordovician metasedimentary materials are presented. 

scholarly journals The Imbert Formation of northern Hispaniola: a tectono-sedimentary record of arc-continent collision and ophiolite emplacement in the northern Caribbean subduction-accretionary prism

2015 ◽  
Vol 7 (2) ◽  
pp. 1827-1876 ◽  
Author(s):  
J. Escuder-Viruete ◽  
A. Suárez-Rodríguez ◽  
J. Gabites ◽  
A. Pérez-Estaún
Keyword(s):  
Subduction Zone ◽  
Continental Margin ◽  
Middle Eocene ◽  
Accretionary Prism ◽  
Island Arc ◽  
Caribbean Island ◽  
Stratigraphic Sequence ◽  
Oblique Collision ◽  
The Caribbean ◽  
Ophiolitic Complex

Abstract. In northern Hispaniola, the Imbert Formation (Fm) has been interpreted as an orogenic "mélange" originally deposited as trench-fill sediments, an accretionary (subduction) complex formed above a SW-dipping subduction zone, or the sedimentary result of the early oblique collision of the Caribbean plate with the Bahama Platform in the middle Eocene. However, new stratigraphical, structural, geochemical and geochronological data from northern Hispaniola indicate that the Imbert Fm constitutes a coarsening-upward stratigraphic sequence that records the transition of the sedimentation from a pre-collisional forearc to a syn-collisional piggy-back basin. This piggy-back basin was transported on top of the Puerto Plata ophiolitic complex slab and structurally underlying accreted units of the Rio San Juan complex, as it was emplaced onto the North America continental margin units. The Imbert Fm unconformably overlies different structural levels of the Caribbean subduction-accretionary prism, including a supra-subduction zone ophiolite, and consists of three laterally discontinuous units that record the exhumation of the underlying basement. The distal turbiditic lower unit includes the latest volcanic activity of the Caribbean island arc; the more proximal turbiditic intermediate unit is moderately affected by syn-sedimentary faulting; and the upper unit is a (caotic) olistostromic unit, composed of serpentinite-rich polymictic breccias, conglomerates and sandstones, strongly deformed by syn-sedimentary faulting, slumping and sliding processes. The Imbert Fm is followed by subsidence and turbiditic deposition of the overlying El Mamey Group. The 40Ar / 39Ar plagioclase plateau ages obtained in gabbroic rocks from the Puerto Plata ophiolitic complex indicate its exhumation at ∼ 45–40 Ma (lower-to-middle Eocene), contemporaneously to the sedimentation of the overlying Imbert Fm. These cooling ages imply the uplift to the surface and submarine erosion of the complex to be the source of the ophiolitic fragments in the Imbert Fm, during of shortly after the emplacement of the intra-oceanic Caribbean island-arc onto the continental margin.

The 1755 Lisbon earthquake and the beginning of closure of the Atlantic

2006 ◽  
Vol 14 (2) ◽  
pp. 193-205 ◽  
Author(s):  
A. RIBEIRO ◽  
L. MENDES-VICTOR ◽  
J. CABRAL ◽  
L. MATIAS ◽  
P. TERRINHA
Keyword(s):  
Source Area ◽  
Accretionary Prism ◽  
Sumatra Earthquake ◽  
Alert System ◽  
Tsunami Modelling ◽  
2004 Sumatra Earthquake ◽  
Lisbon Earthquake ◽  
History Of ◽  
History Of Europe ◽  
Gorringe Bank

The 1755 Lisbon earthquake and tsunami had one of the highest magnitudes in the history of Europe. The source mechanism requires generation at a subduction zone. Intensity distribution and tsunami modelling excludes the Gorringe Bank as a source area and suggests generation by the incipient convergence of the Atlantic with the Southwest Iberia and Morocco margin rather than at the less active Gulf of Cadiz Accretionary Prism. The comparison with the 2004 Sumatra earthquake and tsunami supports this interpretation. A tsunami warning alert system is urgent for the Atlantic.

Paleogeography of the Matapédia basin in the Gaspé Appalachians: initiation of the Gaspé Belt successor basin

2004 ◽  
Vol 41 (5) ◽  
pp. 553-570 ◽  
Author(s):  
Michel Malo
Keyword(s):  
Carbonate Platform ◽  
Source Area ◽  
Turbidity Currents ◽  
Northern Limit ◽  
Fine Grained ◽  
The North ◽  
Iapetus Ocean ◽  
Thrust Sheets ◽  
Siliciclastic Rocks ◽  
Lime Muds

The Matapédia basin consists of the uppermost Ordovician – lowermost Silurian deep-water, fine-grained carbonate–siliciclastic rocks of the Honorat (Garin Formation) and Matapédia groups (Pabos and White Head formations), the lower rock assemblage of the Gaspé Belt in the Gaspé Appalachians. Paleogeographic maps of eight time slices from the Caradocian to the Llandoverian are presented to better understand the tectonosedimentary evolution of the Matapédia basin. Deposition evolved from siliciclastic (Garin Fm.) to argillaceous limestones (Pabos Fm.), to limestones (White Head Fm.). The overall change from terrigenous (Garin Fm.) to limestone facies (White Head Fm.) reflects a change in the source area. Paleocurrent directions and composition of sandstones indicate an orogenic source area to the south for the Garin Formation, which is believed to be the inliers of the Humber and Dunnage zones in the southern Gaspé and New Brunswick Appalachians. Lime muds deposited by turbidity currents coming from the north suggest the Anticosti active carbonate platform as the source area for the White Head Formation. The Matapédia basin was filled from south to north. First deposits, the Garin Formation, occurred south of the Taconian thrust sheets (Humber Zone) and also south of the Grenville basement. This region was the domain of the Ordovician Iapetus Ocean (Dunnage Zone). The northern limit of the basin migrated northward during deposition of the Matapédia Group in Ashgillian–Llandoverian times and reached its actual northern limit at the very end of the Llandoverian (C6), when siliciclastic facies of the lower Chaleurs Group were deposited.

scholarly journals Petrography of the quartz sand deposits of the Lower Cretaceous of Bornholm, Denmark

1986 ◽  
Vol 10 ◽  
pp. 1-24
Author(s):  
Peter Gravesen
Keyword(s):  
Quartz Sand ◽  
Lower Cretaceous ◽  
Source Area ◽  
Source Rocks ◽  
Heavy Minerals ◽  
Fault Block ◽  
Basement Rocks ◽  
Provenance Areas ◽  
Lowermost Part ◽  
Shape Analyses

The quartz sand of the Lower Cretaceous Robbedale Formation and lowermost part of the Jydegard Formation in the Arnager-Sose fault block of Bornholm has been investigated with respect to mineralogy, grain-size, grain rounding and grain shape. Analyses of both light and heavy minerals have been carried out for 18 samples from different localities and facies. The purpose of the investigation was to try to recognize the possible types of source rocks and provenance areas. The Precambrian basement rocks of Bornholm are not the main sources of the sand, especially not the heavy minerals, but parts of the sand may have originated from the basement. The Palaeozoic sandstones and siltstones have delivered only a small amount of material. Parts of the older Mesozoic sediments of the Bornholm Group and Homandshald Member may have been redeposited in the Lower Cretaceous as they contain the same kinds of heavy minerals as the Robbedale and Jydegard Formations, although in differing amounts. It seems very possible, however, that most of the Mesozoic sediments of Bornholm have had a source area outside Bornholm, and this source area has been nearly the same during the whole span of time. The Fenno-Scandian Shield seems to be the most obvious provenance area, but eastern and southern areas are possibilities too. It is concluded that most of the Lower Cretaceous sands are first deposition cycle sediments of both local and distant origin combined with minor amounts of polycyclic sediments of mainly local origin.

scholarly journals Tectono-stratigraphic evolution of the Southern Campania Margin: a key area for the evolution of the Tyrrhenian-Apennine system

2018 ◽  
Vol 73 ◽  
pp. 39 ◽  
Author(s):  
Pietro Iannace ◽  
Maurizio M. Torrente ◽  
Alfonsa Milia
Keyword(s):  
Early Stage ◽  
Accretionary Prism ◽  
Tyrrhenian Sea ◽  
Central Mediterranean ◽  
Deep Wells ◽  
Transport Direction ◽  
Thrust Sheets ◽  
Gis Environment ◽  
Extension Direction ◽  
Stratigraphic Evolution

The Southern Campania Margin (SCM) represents a key area of the Central Mediterranean because it records all the rifting stages of the Tyrrhenian Sea. The interpretation of a seismic dataset calibrated with deep wells and outcrops, using seismic stratigraphy and structural geology methods in a dedicated Geographic Information System (GIS) environment, the seismic depth conversion, the generation of 2-D and 3-D models led to the reconstruction of a polyphased tectono-stratigraphic evolution of the SCM. During the early stage of Tyrrhenian opening a terrigenous transtensional Basin (Langhian-Tortonian Cilento Basin) formed on the Liguride accretionary prism adjacent to the Calabria crystalline terrane. In the SCM the Liguride thrust sheets tectonically overly the Apennine Platform units and both these nappes have been dismembered by Quaternary faults. Three rifting stages, not homogeneously distributed, affected the region since the Lower Pleistocene. They are associated to the deposition of a thick Quaternary succession (A, B and C units). During these Pleistocene stages there was an abrupt change of the extension direction (from NE-SW to NW-SE) accompanying a change of the nappe transport direction of the Southern Apennines. The construction of balanced sections using dedicated software, permitted us to recognize the true geometry of the faults and compute the amount of Quaternary extension of the SCM that results comparable to those calculated for other sectors of the Tyrrhenian margin and further extensional regions worldwide.

Detrital zircon age fingerprinting of NW and SW Iberia Variscan basins: Constraints for the pre-Pangea terrane assemblage analysis and paleogeography

2020 ◽  
Author(s):  
Ícaro Dias da Silva ◽  
Manuel Francisco Pereira ◽  
Emílio González Clavijo ◽  
José R. Martínez Catalán ◽  
Juan Gómez Barreiro ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Detrital Zircon ◽  
Sedimentary Basins ◽  
Zircon Age ◽  
Drainage Systems ◽  
Middle Ordovician ◽  
Source Areas ◽  
Provenance Studies ◽  
Sedimentary Environments ◽  
Nw Iberia

<p>Synorogenic basins could be linked to a wide variety of sedimentary environments, from continental to deep-marine, in distinct geodynamic settings. The sedimentary evolution of synorogenic basins is mainly controlled by the existence of relief rejuvenation and denudation within and in the surroundings areas. Accumulation of sediment in such basins could react to changes in tectonic settings. Successive extensional or contractional events that are common during the formation of an orogenic belt can induce variations on basin depth, basin depocenter migration and/or repetition of sedimentation-erosion cycles.</p><p>Detrital zircon age fingerprinting of sedimentary basins has proven to be a very sensitive tool for analyzing large and local scale changes in source-terranes, contributing to refine regional paleogeographic models. Recognition of potential source areas could be done by using statistically robust techniques. Kolmogorov-Smirnoff test (K-S) and Multidimensional Scaling (MDS) has been successfully applied to define the fingerprints of sedimentary rocks using detrital zircon age populations and compare with those from potential terrane sources. Comparative statistical analysis of detrital zircon age populations from particular sources and basin strata may be useful to prove sedimentary provenance and distance from source areas, to identify intra-basin sediment recycling and to track multi-source mixing along drainage systems.</p><p>During the Late Devonian-Carboniferous amalgamation of Pangea extensive marine sedimentation occurred in the Variscan orogen on both Laurussia and Gondwana collision margins. Remains of such synorogenic basins are currently located in different sectors of the European Variscan belt, including Iberia.</p><p>Recent provenance studies conducted in SW Iberia Variscan basins have distinguished the contribution of three distinct terrane sources “Gondwana-”, “Laurussia-” and “Variscan magmatic arc-” types, in some cases admitting sediment recycling and mixing of sources. Statistical analysis of detrital zircon age population from NW Iberia Variscan basin allowed us to distinguish two major sources a “Middle Ordovician-Silurian magmatic episode”-type and a “Gondwana”-type. These two types appear to correspond to source areas belonging to the nearby autochthonous and allochthonous units. Gondwanan-type source includes six sub-types whose contributions varied throughout synorogenic basins evolution, indicating that where sedimentary recycling seems to have been relevant.</p><p>Provenance studies on Variscan basins proved to be essential to test if whether or not NW Iberia and SW Iberia synorogenic basins have developed in geographical proximity of Paleozoic Laurussian- or Gondwanan-terrane sources. The differences found between the sources of NW and SW Variscan basins suggest that they would be geographically separated and influenced by independent drainage systems. This finding has provided a better understanding of the framing of Iberia synorogenic basins in paleographic models of Pangea amalgamation.</p><p>Acknowledgements: This study was supported by SYNTHESIS3 project DE-TAF-5798, by “Estímulo ao Emprego Científico – Norma Transitória” by CGL2016-78560-P (MICINN) and by FCT- project UID/GEO/50019/2019 - Instituto Dom Luiz.</p>

VI.—The Petrology and Sedimentation of Upper Ordovician Rocks in the Rhinns of Galloway, South-west Scotland

1962 ◽  
Vol 65 (6) ◽  
pp. 107-137 ◽  
Author(s):  
Gilbert Kelling
Keyword(s):  
Source Area ◽  
Heavy Minerals ◽  
Coarse Grained ◽  
Upper Ordovician ◽  
Rock Fragments ◽  
North East ◽  
The North ◽  
South West ◽  
Wide Range ◽  
Nearby Source

SynopsisThe petrology of a group of geosynclinal rudites and arenites of Upper Ordovician age from the Rhinns of Galloway, south-west Scotland, is described. The rudites are confined to the oldest formation, the Corsewall Group, and consist of pebbly microbreccias and “boulder-beds” interbedded with coarse greywackes and platy siltstones. The composition of the microbreccias and boulder-beds varies little with stratigraphic level.The arenites comprise lithic, coarse-grained greywackes with occasional quartzose or feldspathic varieties. They carry, in aggregate, a wide range of igneous, metamorphic and sedimentary rock-fragments, quartz of variable source, a variety of feldspars, ferromagnesian minerals, micas, chlorites and a common to conspicuous argillaceous matrix. The greywackes are well defined stratigraphically as regards both overall composition and the character of the large mineral grains and rock-fragments (“granules”). Moreover composition appears to be related to grain-size in a consistent manner. The size-distribution, sorting and skewness of the greywackes based on thin section measurements show little stratigraphic variation.The aggregate suite of heavy minerals is meagre and only minor differences exist in the individual formation-suites.The character of the rock-fragments and mineral grains suggests that the earlier formations were derived from a nearby source-area in which plutonic and hypabyssal acid and basic igneous rocks were extensively exposed, together with spilitic lavas and glaucophane schists. The petrology of the upper formations reveals that a metamorphic terrain of Southern Highlands aspect became an important additional source of material. However, the highest beds were derived from a region dominated by andesitic and spilitic tuffs and lavas.The principal directional sedimentary structures are described briefly and it is suggested that the lower part of the Corsewall Group, derived mainly from the north and north-east, was deposited in a sheltered pro-delta environment, but that the boulder-beds and associated rocks were formed within a more boisterous region. The Kirkcolm Group is a turbidite-sequence deposited in a marine trough of moderate depth by currents which at first flowed dominantly in opposing directions, towards either north-east or south-west. However, transport from the north-east became progressively established. The Portpatrick Group is another turbidite-sequence but this formation was deposited by currents flowing from the west or south-west.

Highly mature sediments in the tropical monsoonal environment of southwestern India: an appraisal based on weathering indices

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Linu Babu ◽  
S. Vishnu Mohan ◽  
Mahesh Mohan ◽  
A.P. Pradeepkumar
Keyword(s):  
Major Element ◽  
Practical Implication ◽  
Source Area ◽  
Major Elements ◽  
Climatic Conditions ◽  
Element Geochemistry ◽  
Content Type ◽  
Electron Probe Micro Analyzer ◽  
Chemical Index ◽  
Provenance Areas

Purpose This paper aims to examine the geochemical change experienced by laterites in Kerala, India, subjected to tropical monsoonal climate. These sediments are underlain by hard rock. The source rock characteristics have a major stake on the ultimate composition of sediments, as also the climatic conditions which an area experience. Design/methodology/approach Core samples have been obtained from several locations in a lateritic plateau. The upper portions of the borehole cores are composed of the lateritic hard cap, followed by lateritic soils. The soil samples were subjected to sediment texture analysis and XRF analysis (Bruker S4 Pioneer Sequential Wavelength-Dispersive XRF) for the determination of major elements ((in oxide form). Findings Major element geochemistry has revealed the following order of relative proportions of elements (in oxide form) SiO2 > Al2O3 > Fe2O3 > TiO2 >> Na2O > P2O5 > CaO > K2O > MgO > MnO. Even though the concentrations of SiO2, Al2O3 and Fe2O3 contribute 90% of major element chemistry, there is no significant correlation found for these elements within themselves or with others. Research limitations/implications Microscale movement of elements could not be characterised in this study. This requires access to an electron probe micro analyzer. Practical implications The practical implication of tropical weathering is that enhanced chemical leaching leads to movement of most elements out of the system, except for Al, leading to the possible formation of bauxite, or aluminous laterite. Social implications The weathered products in this study provide livelihood sustenance for many of the local households, through manual production of laterite bricks, which are used in construction. Originality/value The indices of the intensity of chemical alteration/weathering like chemical index of alteration (CIA), chemical index of weathering (CIW) and weathering index of parker (WIP) reveal that the sediments indicate intense weathering of the source area prior to being deposited in the present location. This indicates enhanced monsoonal activity in the provenance areas, than that obtained today.

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