Using elemental geochemistry, clay mineralogy, grain size end-member modeling, and planktonic foraminiferal δ18O, we characterize the provenance of central-Mediterranean sediments over the past 18 ka. The provenance is dust-dominated before and after the African Humid Period (AHP). By contrast, during the AHP (∼11–5 ka), largely concurrent with organic-rich sapropel S1 formation, it is predominantly riverine from North-African sources. Such fluvial supply is suggested to come from paleodrainage networks that were reactivated by intensified monsoon precipitation during the AHP. The supply is characterized by high Mg/Al and smectite contents, and has been accompanied by considerable freshwater influx, as indicated by the enhanced grain size and lighter foraminiferal δ18O. The clay-mineral assemblages in our core and in nearby cores correspond with a provenance from the Libyan-Tunisian margin, mainly via the paleo-river Irharhar. The inferred fluvial discharge is strongest during the late-AHP (∼8–5.5 ka), coinciding with reported enhanced fluvial dynamics and wettest conditions over western Libya and Tunisia/Algeria. This period is not only synchronous with the largest extension of open-water bodies in North Africa and lowest Saharan dust inputs, but also consistent with precipitation records of the West-African monsoon. Moreover, our records show a remarkable correspondence with that of a paleodrainage system towards the Atlantic West-African margin, inferring a common headwater region in the central Saharan mountains, and a similar climate mechanism. Taken together, we suggest a dominant control of North-African humid surfaces on the paleodrainage delivery, modulated by groundwater level, in response to the insolation-driven West-African monsoon precipitation. © 2017 Elsevier Ltd

North-African paleodrainage discharges to the central Mediterranean during the last 18,000 years: A multiproxy characterization

Schirone, A.
2017

Abstract

Using elemental geochemistry, clay mineralogy, grain size end-member modeling, and planktonic foraminiferal δ18O, we characterize the provenance of central-Mediterranean sediments over the past 18 ka. The provenance is dust-dominated before and after the African Humid Period (AHP). By contrast, during the AHP (∼11–5 ka), largely concurrent with organic-rich sapropel S1 formation, it is predominantly riverine from North-African sources. Such fluvial supply is suggested to come from paleodrainage networks that were reactivated by intensified monsoon precipitation during the AHP. The supply is characterized by high Mg/Al and smectite contents, and has been accompanied by considerable freshwater influx, as indicated by the enhanced grain size and lighter foraminiferal δ18O. The clay-mineral assemblages in our core and in nearby cores correspond with a provenance from the Libyan-Tunisian margin, mainly via the paleo-river Irharhar. The inferred fluvial discharge is strongest during the late-AHP (∼8–5.5 ka), coinciding with reported enhanced fluvial dynamics and wettest conditions over western Libya and Tunisia/Algeria. This period is not only synchronous with the largest extension of open-water bodies in North Africa and lowest Saharan dust inputs, but also consistent with precipitation records of the West-African monsoon. Moreover, our records show a remarkable correspondence with that of a paleodrainage system towards the Atlantic West-African margin, inferring a common headwater region in the central Saharan mountains, and a similar climate mechanism. Taken together, we suggest a dominant control of North-African humid surfaces on the paleodrainage delivery, modulated by groundwater level, in response to the insolation-driven West-African monsoon precipitation. © 2017 Elsevier Ltd
Inorganic geochemistry;Quaternary;Sapropel S1;North Africa;Provenance;Paleodrainage systems;Paleoclimatology;African humid period;Grain size end-member modeling;Clay minerals
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.12079/1787
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus ND
social impact