New detrital petrographic and thermochronologic constraints on the Late Cretaceous-Neogene erosional history of the equatorial margin of Brazil: Implications for the surface evolution of a complex rift margin

The equatorial margin of Brazil is an example of a rift margin with a complex landscape, dominated by an escarpment perpendicular to the continental margin, which testifies to an equally complex rift and post-rift surface and tectonic evolution. This has been the focus of a long debate on the driving mechanism for post-rift tectonics and on the amount of exhumation. This study contributes to this debate with new petrographic and thermochronologic data on 152 samples from three basins, Para-Maranhao, Barreirinhas and Ceara, on the offshore continental platform. Our detrital record goes back to the rift time at ca. 100 Ma ago and outlines three major evolutionary phases of a changing landscape: a rift phase, with the erosion of a moderate rift escarpment, a Late Cretaceous-Palaeogene post-rift phase of major drainage reorganization and significant vertical erosion and a Late Oligocene-to-Recent post-rift phase of moderate vertical erosion and river headwater migration. We estimate that along the equatorial margin of Brazil, over a large onshore area, exhumation since the Late Cretaceous has totalled locally up to 2-2.5 km and since the late Oligocene did not exceed 1 km

Palaeogeography of the Upper Cretaceous-Eocene carbonate turbidites of the Northern Apennines from provenance studies

The Upper Cretaceous Helminthoid Flysch (HF) of the Northern Apennines consists of thick and regionally widespread deep-water carbonate turbidite successions, deposited during theinitial stages of Alpine collision. The HF spans the time from Campanian to Early Eocene and is mainly composed of intrabasinal carbonate ooze mixed with clay; siliciclastic terrigenous beds arealso present, but they are a volumetrically minor component of the successions. Petrographic and sedimentological signatures indicate that the HF was deposited in distinct basins located below thecarbonate compensation depth. Bulk composition and heavy minerals of terrigenous beds indicate provenance from different crustal levels of the European and Adria plates. The petrographic andpalaeobathymetric characteristics of these turbidites indicate the coexistence of an active-margin tectonic setting, a palaeogeographical position suitable for carbonate ooze production and storage,and limited supply of terrigenous detritus into the basin. Palaeotectonic reconstructions and stratigraphic data suggest that Adria represented a vast repository of penecontemporaneous carbonate mud; the presumably intense seismic activity related to the pre-collisional Alpine orogeny promoted large-scale failures of shelf or slope biogenic muddy sediments, resulting in the depositionof a large volume of carbonate turbidites. Only occasionally, turbidity currents probably linked to exceptional fluvial floods generated pure terrigenous beds with different petrographic signatures for each HF succession

Tectonically controlled sedimentation: impact on sediment supply and basin evolution of the Kashafrud Formation (Middle Jurassic, Kopeh-Dagh Basin, northeast Iran)

peer reviewedThe Kashafrud Formation was deposited in the extensional Kopeh-Dagh Basin during the Late Bajocian to Bathonian (Middle Jurassic) and is potentially the most important siliciclastic unit from NE Iran for petroleum geology. This extensional setting allowed the accumulation of about 1,700 m of siliciclastic sediments during a limited period of time (Upper Bajocian–Bathonian). Here, we present a detailed facies analysis combined with magnetic susceptibility (MS) results focusing on the exceptional record of the Pol-e-Gazi section in the southeastern part of the basin. MS is classically interpreted as related to the amount of detrital input. The amount of these detrital inputs and then the MS being classically influenced by sea-level changes, climate changes and tectonic activity. Facies analysis reveals that the studied rocks were deposited in shallow marine, slope to pro-delta settings. A major transgressive–regressive cycle is recorded in this formation, including fluvial-dominated delta to turbiditic pro-delta settings (transgressive phase), followed by siliciclastic to mixed siliciclastic and carbonate shoreface rocks (regressive phase). During the transgressive phase, hyperpycnal currents were feeding the basin. These hyperpycnal currents are interpreted as related to important tectonic variations, in relation to significant uplift of the hinterland during opening of the basin. This tectonic activity was responsible for stronger erosion, providing a higher amount of siliciclastic input into the basin, leading to a high MS signal. During the regressive phase, the tectonic activity strongly decreased. Furthermore, the depositional setting changed to a wave- to tide-dominated, mixed carbonate–siliciclastic setting. Because of the absence of strong tectonic variations, bulk MS was controlled by other factors such as sea-level and climatic changes. Fluctuations in carbonate production, possibly related to sea-level variations, influenced the MS of the siliciclastic/carbonate cycles. Carbonate intervals are characterized by a strong decrease of MS values indicates a gradual reduction of detrital influx. Therefore, the intensity of tectonic movement is thought to be the dominant factor in controlling sediment supply, changes in accommodation space and modes of deposition throughout the Middle Jurassic sedimentary succession in the Pol-e-Gazi section and possibly in the Kopeh-Dagh Basin in general

Groundwater flow systems in turbidites of the Northern Apennines (Italy): natural discharge and high speed railway tunnel drainage

A conceptual model of groundwater flow systems in turbiditic fractured aquifers is proposed, taking into account natural discharge pattern of the hydrogeologic system and the system perturbation induced by tunnel drainage. Silico-clastic and marly calcareous turbidites outcrop extensively in Northern Apeninnes (Italy) and paper deals with the assessment of the aquifer-like behaviour of these units, up to now considered as aquitards, as reflected by the huge amounts of groundwater locally drained by tunnels for the high speed railway (HSR) connection between Bologna and Florence. The study is based on the analysis of a huge amount of hydrological data (springs, streams and tunnels discharge) collected by a monitoring activity performed for a 10 years time-span, integrated by hydrochemical and isotopic analysis on surface and tunnel waters and a stream-tunnel tracer test. In a turbiditic aquifer recession analysis permits to discriminate groundwater flow systems, to calculate recharge relative to the up-stream reach portion and to locate springs more vulnerable to tunnel drainage impacts. Natural discharge is stream-focused and, as the tunnel drainage is for 85% formed by active recharge groundwater, the impact on the stream base-flow is severe with abatement of natural discharge budget component up to 2/3 of natural value

The External Tanger Unit (Intrarif sub-Domain, External Rifian Zones, Morocco): an interdisciplinary study

The External Tanger Unit represents one of the most complete Cretaceous-Miocene successions in the central areas of the Internal Intrarif sub-Domain (External Rif Zones, Morocco). An interdisciplinary study has been carried out to propose a new characterization of this unit which would allow a better comprehension of the confused and complex relationships among different units of the same sub-domain. The results achieved can be summarized as follows: (1) redefinition of the stratigraphic (litho-, bio-, and chrono-) record and introduction of a new, informal lithostratigraphic terminology; (2) recognition of two main depositional sequences (lower-middle Eocene p.p. and lower Oligocene p.p.-lower Miocene p.p.) separated by extended gaps (latest Cretaceous-early Eocene p.p. and middle Eocene p.p.-early Oligocene p.p.); (3) reconstruction of the evolution of the sedimentary realm, and of the relationships between tectonics and sedimentation; and (4) comparison between the upper Cretaceous-Miocene stratigraphic record and tectonic events of the Intrarif, which is located in the western external portion of the Maghrebian Flysch Basin, and the equivalent sedimentary record of the eastern portion of this basin in the Tunisian Tell. More in general, our results allowed (i) a first reconstruction of the Cretaceous-Miocene main tectono-sedimentary events; (ii) a more detailed location of the sedimentary suite in the external African Margin in the context of a wider palaeogeographic framework; and (iii) the definition of the main stages of the geological evolution of the area.Research supported by: Research Project CGL2016-75679-P, Spanish Ministry of Education and Science; Research Groups and Projects of the Generalitat Valenciana, Alicante University (CTMAIGA); Research Group RNM 146, Junta de Andalucía; grants from the University of Urbino Carlo Bo, responsible M. Tramontana

Sediments of the Moon and Earth as End-Members for Comparative Planetology

Processes of production, transport, deposition, lithification, and preservation of sediments of the Moon and Earth are extremely different. The differences arise primarily from the dissimilarity in the origins and sizes of the Moon and Earth. The consequence is that the Moon does not have an atmosphere, a hydrosphere (the Moon is totally dry), a biosphere (the Moon is totally life-less), a magnetosphere, and any tectonic force. Pristine rocks on the exposed surface of the Moon are principally anorthositic and basaltic, but those on the Earth are granitic (discounting suboceanic rocks). Sediments on these two bodies probably represent two end-members on rocky planetary bodies. Sediments on other rocky planetary bodies (atmosphere-free Mercury and asteroids, Venus with a thick atmosphere but possibly no water on its surface, and Mars with a currently dry surface sculptured by running water in the past) afe intermediate in character. New evidence suggests that characteristics of Martian sediments may be in-between those of the Moon and Earth. For example, impacts generate most Martian sediments as on the Moon, and, Martian sediments are wind-blown to form dunes as on Earth. A comparative understanding of sediments of the Moon and Earth helps us anticipate and interpret the sedimentary record of other planetary bodies. Impact processes, large and small, have produced the sediments of the Moon. Unlike Earth, the surface of the Moon is continuously bombarded by micrometeorites and solar wind. Processes of chemical and mechanical weathering aided by biological activity produce sediments on Earth, fixing a significant amount of carbon in the solid state. Whereas solar wind produces minor chemical changes in lunar sediments, chemical weathering significantly alters and affects the character of Earth sediments. Primarily ballistic and electrostatic forces transport lunar sediments but Earth sediments are transported by air, water, and ice. Whereas Earth sediments accumulate mostly in basins created slowly by tectonic forces, lunar sediments are deposited in craters (excavated instantaneously by impacts) or even on high grounds. Rubble, sand, mud, and carbonate material on Earth are lithified through burial, expulsion of water, and precipitation of cement from H2O-so1utions. In contrast, lunar sediments are lithified through presumably low-energy shock waves that sinter and bind clastic grains into regolith breccias. Surface processes and morphological features on the Moon are dominated by impact cratering and ejecta deposition, while those on Earth are sculptured by water, ice, and air. However, comparisons in two areas assist in planning planetary exploration. (l) Dust, i.e., small particles elevated above the solid surface of a planetary body, is ubiquitous on the Moon and Earth. The composition of dust is related to but is different from the source rocks, especially where dust is transported aver long distances as on Earth. Dust obscures observation of a planetary body and interferes with remote sensing; dust may also affect climate on planetary bodies with an atmosphere. (2) Because Earth's lithosphere has been recycled many times, sediments shed from rocks and regions that do not exist any more are the principal guides to the ancient Earth and its crustal evolution. Because the lunar surface is completely covered by regolith, and no bedrock has been directly observed or sampled, sediment is the principal guide to the lunar crust, past and presento Provenance analysis of lunar and terrestrial sediments is accomplished using the same methods and principles