Pronounced Northwest African Monsoon Discharge During the Mid- to Late Holocene

Höpker, Sebastian N.; Wu, Henry C.; Müller, Péter; Barusseau, Jean-Paul; Vernet, Robert; Lucassen, Friedrich; Kasemann, Simone A.; Westphal, Hildegard

doi:10.3389/feart.2019.00314

Front. Earth Sci.

2019

DOI: 10.3389/feart.2019.00314

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Pronounced Northwest African Monsoon Discharge During the Mid- to Late Holocene

Sebastian N. Höpker

¹

,

Henry C. Wu

²

,

Péter Müller

³

et al.

Abstract: The mid-to late Holocene aridification pattern of NW Africa remains a matter of controversial debate. While many marine climate reconstructions indicate a relatively abrupt aridification at ∼5.5 ka BP, terrestrial palaeoclimate records rather show a spatially and temporally heterogeneous transition towards the modern arid state. To bridge conflicting evidence, we analysed high-resolution (sub-seasonal) ontogenetic oxygen isotope (δ 18 O) records and bulk 87 Sr/ 86 Sr ratios of bivalve shells and fish otoliths … Show more

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Cited by 9 publications

(17 citation statements)

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“…Sedimentary facies and pollen deposition during this stage were principally driven by the interaction between the creation of accommodation space and density of mangrove vegetation spread across the nearshore realm (Bonne, 2014) (Figures 6 and 7). On a regional extent, delta retrogradation correlates to the period of sea level rise (Nouakchottian transgression) as observed from the coastal margins of Congo, Senegal and Mauritania (Adojoh and Dada, 2015; Barusseau et al, 1988, 1995; Dalibard et al, 2014; Höpker et al, 2019; Lézine, 1997; Lézine and Denèfle, 1997; Scourse et al, 2005). In addition, this setting suggests a proximal-upper shoreface (delta plain/delta front) palaeoenvironment based on the dominance of the planktonic foraminiferal ( Globorotalia spp., Globigerinoides ruber ) (Figure 8).…”

Section: Discussionmentioning

confidence: 93%

“…It provides evidence of dry conditions and fluvial sediment supply to 2-5). In addition, the observed fluvial sediment supply could be linked to the seasonal latitudinal migration of the Intertropical Convergent Zone (ITCZ) with a mean annual position assumed to be around 15°N positioned further south (15°S) (Höpker et al, 2019;Kim et al, 2010;Leroux, 1993;Marret et al, 2001;Shanahan et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

“…It provides evidence of dry conditions and fluvial sediment supply to the Niger Delta based on abundant records of the catchment (Ti/Zr ratio) and hinterland (Poaceae, cuticle) indicators interpreted from the lower part of the GCs (Abbink et al, 2004; Adegbie et al, 2003; Adeonipekun and Sowunmi, 2019; Adojoh et al, 2017; Morley and Richards, 1993; Pastouret et al, 1978; Skonieczny et al, 2015; Zabel et al, 2001; Figures 2–5). In addition, the observed fluvial sediment supply could be linked to the seasonal latitudinal migration of the Intertropical Convergent Zone (ITCZ) with a mean annual position assumed to be around 15°N positioned further south (15°S) (Höpker et al, 2019; Kim et al, 2010; Leroux, 1993; Marret et al, 2001; Shanahan et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

“…and marine indicators (Fe/S ratio) in the GC depths of ~202–0 cm (Figures 2–5). This was a set of both rapid spread of the coastal/littoral vegetation zone and marine organically related iron-sulphur preservation associated with sea level rise and linked to the gently sloping shelf where transgressive sedimentation took place, leading to delta plain retreat (Adeonipekun and Sowunmi, 2019; Adojoh et al, 2015; Amorosi et al, 2014; Höpker et al, 2019; Lézine, 1997; Rull, 2002; Scourse et al, 2005; Torricelli et al, 2006). These depths also experienced increased marine (tidal) influence when compared to lower depths (GC depths of ~272–202) (Figures 2–5), implying that marine organically rich iron-sulphur (Fe/S) and mangrove pollen preservation in intertidal- tidal settings would be much higher (Joo-Chang et al, 2015; Punwong et al, 2013; Rull, 2002; Figures 6 and 7).…”

Section: Discussionmentioning

confidence: 99%

“…Following delta retrogradation (stage 1) was a period of rapid sediment retreat in the Niger Delta attributed to sea level rise (Figures 6-8). This period of onset of Early to Mid-Holocene sea level rise and warm climate coincides with an episode of shoreline transgression and fine-grain (clay, silt, very fine sand) sediment suspension reflecting the proximity of turbidity currents (Goodbred, 2003;Höpker et al, 2019;Joo-Chang et al, 2015;Peltier, 1994;Scourse et al, 2005). Increases in the values of Fe/S elemental tracer as opposed Ti/Zr ratio suggests a reducing environment with the potential of rapid post-dissolution of pyrite (FeS) minerals and organic-rich sulphur content (Fletcher, 2005;Mendoza, 2007).…”

Section: Climate and Sea Level Change Controls As An Expression Of Pa...mentioning

confidence: 92%

See 4 more Smart Citations

Stages of palaeoenvironmental evolution, climate and sea level change of the Niger Delta, east Equatorial Atlantic: Novelty from elemental tracers, sedimentary facies and pollen records

Adojoh

¹

,

Marret

²

,

Duller

³

et al. 2023

Get access via publisher Add to dashboard Cite

Exaggerated anticipatory anxiety is common in social anxiety disorder (SAD). Neuroimaging studies have revealed altered neural activity in response to social stimuli in SAD, but fewer studies have examined neural activity during anticipation of feared social stimuli in SAD. The current study examined the time course and magnitude of activity in threat processing brain regions during speech anticipation in socially anxious individuals and healthy controls (HC). Method Participants (SAD n = 58; HC n = 16) underwent functional magnetic resonance imaging (fMRI) during which they completed a 90s control anticipation task and 90s speech anticipation task.

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“…Sedimentary facies and pollen deposition during this stage were principally driven by the interaction between the creation of accommodation space and density of mangrove vegetation spread across the nearshore realm (Bonne, 2014) (Figures 6 and 7). On a regional extent, delta retrogradation correlates to the period of sea level rise (Nouakchottian transgression) as observed from the coastal margins of Congo, Senegal and Mauritania (Adojoh and Dada, 2015; Barusseau et al, 1988, 1995; Dalibard et al, 2014; Höpker et al, 2019; Lézine, 1997; Lézine and Denèfle, 1997; Scourse et al, 2005). In addition, this setting suggests a proximal-upper shoreface (delta plain/delta front) palaeoenvironment based on the dominance of the planktonic foraminiferal ( Globorotalia spp., Globigerinoides ruber ) (Figure 8).…”

Section: Discussionmentioning

confidence: 93%

“…It provides evidence of dry conditions and fluvial sediment supply to 2-5). In addition, the observed fluvial sediment supply could be linked to the seasonal latitudinal migration of the Intertropical Convergent Zone (ITCZ) with a mean annual position assumed to be around 15°N positioned further south (15°S) (Höpker et al, 2019;Kim et al, 2010;Leroux, 1993;Marret et al, 2001;Shanahan et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

“…It provides evidence of dry conditions and fluvial sediment supply to the Niger Delta based on abundant records of the catchment (Ti/Zr ratio) and hinterland (Poaceae, cuticle) indicators interpreted from the lower part of the GCs (Abbink et al, 2004; Adegbie et al, 2003; Adeonipekun and Sowunmi, 2019; Adojoh et al, 2017; Morley and Richards, 1993; Pastouret et al, 1978; Skonieczny et al, 2015; Zabel et al, 2001; Figures 2–5). In addition, the observed fluvial sediment supply could be linked to the seasonal latitudinal migration of the Intertropical Convergent Zone (ITCZ) with a mean annual position assumed to be around 15°N positioned further south (15°S) (Höpker et al, 2019; Kim et al, 2010; Leroux, 1993; Marret et al, 2001; Shanahan et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

“…and marine indicators (Fe/S ratio) in the GC depths of ~202–0 cm (Figures 2–5). This was a set of both rapid spread of the coastal/littoral vegetation zone and marine organically related iron-sulphur preservation associated with sea level rise and linked to the gently sloping shelf where transgressive sedimentation took place, leading to delta plain retreat (Adeonipekun and Sowunmi, 2019; Adojoh et al, 2015; Amorosi et al, 2014; Höpker et al, 2019; Lézine, 1997; Rull, 2002; Scourse et al, 2005; Torricelli et al, 2006). These depths also experienced increased marine (tidal) influence when compared to lower depths (GC depths of ~272–202) (Figures 2–5), implying that marine organically rich iron-sulphur (Fe/S) and mangrove pollen preservation in intertidal- tidal settings would be much higher (Joo-Chang et al, 2015; Punwong et al, 2013; Rull, 2002; Figures 6 and 7).…”

Section: Discussionmentioning

confidence: 99%

“…Following delta retrogradation (stage 1) was a period of rapid sediment retreat in the Niger Delta attributed to sea level rise (Figures 6-8). This period of onset of Early to Mid-Holocene sea level rise and warm climate coincides with an episode of shoreline transgression and fine-grain (clay, silt, very fine sand) sediment suspension reflecting the proximity of turbidity currents (Goodbred, 2003;Höpker et al, 2019;Joo-Chang et al, 2015;Peltier, 1994;Scourse et al, 2005). Increases in the values of Fe/S elemental tracer as opposed Ti/Zr ratio suggests a reducing environment with the potential of rapid post-dissolution of pyrite (FeS) minerals and organic-rich sulphur content (Fletcher, 2005;Mendoza, 2007).…”

Section: Climate and Sea Level Change Controls As An Expression Of Pa...mentioning

confidence: 92%

See 3 more Smart Citations

Stages of palaeoenvironmental evolution, climate and sea level change of the Niger Delta, east Equatorial Atlantic: Novelty from elemental tracers, sedimentary facies and pollen records

Adojoh

¹

,

Marret

²

,

Duller

³

et al. 2023

Get access via publisher Add to dashboard Cite

Exaggerated anticipatory anxiety is common in social anxiety disorder (SAD). Neuroimaging studies have revealed altered neural activity in response to social stimuli in SAD, but fewer studies have examined neural activity during anticipation of feared social stimuli in SAD. The current study examined the time course and magnitude of activity in threat processing brain regions during speech anticipation in socially anxious individuals and healthy controls (HC). Method Participants (SAD n = 58; HC n = 16) underwent functional magnetic resonance imaging (fMRI) during which they completed a 90s control anticipation task and 90s speech anticipation task.

show abstract

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