The late Barremian-early Aptian time interval was marked by intense volcanic activity of the Ontong Java Plateau (OJP) which induced a global perturbation in the ocean-atmosphere system culminating in the early Aptian Oceanic Anoxic Event (OAE) 1a. Several studies reconstructed temperature variations across OAE 1a and provided evidence for a major warming interrupted by transient ‘cold snaps’. The climatic conditions for the middle–late Aptian are instead less constrained. Here, we present a reconstruction of surface-water palaeotemperature and fertility based on calcareous nannofossil records from the Tethys and Pacific Ocean. The data, integrated with O-isotope and TEX86 records, provide a detailed picture of climatic and ocean fertility changes during the Aptian, discussed in relation to the role of volcanism. Warm temperatures characterized the pre-OAE 1a interval followed by a maximum warming (of ~3 °C) during the early phase of anoxia under intense activity of the OJP. A short-lived (~35ky) cooling episode interrupted the major warming, following a rapid increase of weathering rates. Nannofossils indicate that mesotrophic conditions were reached when temperatures were at their highest and OJP volcanism most intense. The latter part of OAE 1a was characterized by cooling events, probably promoted by CO2 sequestration via burial of organic matter (OM). The end of anoxia coincided with the cessation of volcanism and a marked cooling. The mid-Aptian was characterized by relatively high surface-water fertility and decreasing temperatures, probably resulting from intense weathering drawing down pCO2. The lowest temperatures and low fertility, were reached in the middle–late Aptian across the interval characterized by blooming of N. truittii. The data presented suggest that OJP played a direct role in inducing global warming during OAE 1a, whereas other mechanisms (weathering, deposition of OM) acted as feedback processes favoring temporary cooler interludes.
Climate variability and relationship with ocean fertility during the Aptian / E. Erba, C. Bottini, D. Tiraboschi, H.C. Jenkyns, S. Schouten, J.S. Sinninghe Damsté. ((Intervento presentato al convegno AGU Fall meeting tenutosi a San Francisco nel 2014.
Climate variability and relationship with ocean fertility during the Aptian
E. ErbaPrimo
;C. BottiniSecondo
;D. Tiraboschi;
2014
Abstract
The late Barremian-early Aptian time interval was marked by intense volcanic activity of the Ontong Java Plateau (OJP) which induced a global perturbation in the ocean-atmosphere system culminating in the early Aptian Oceanic Anoxic Event (OAE) 1a. Several studies reconstructed temperature variations across OAE 1a and provided evidence for a major warming interrupted by transient ‘cold snaps’. The climatic conditions for the middle–late Aptian are instead less constrained. Here, we present a reconstruction of surface-water palaeotemperature and fertility based on calcareous nannofossil records from the Tethys and Pacific Ocean. The data, integrated with O-isotope and TEX86 records, provide a detailed picture of climatic and ocean fertility changes during the Aptian, discussed in relation to the role of volcanism. Warm temperatures characterized the pre-OAE 1a interval followed by a maximum warming (of ~3 °C) during the early phase of anoxia under intense activity of the OJP. A short-lived (~35ky) cooling episode interrupted the major warming, following a rapid increase of weathering rates. Nannofossils indicate that mesotrophic conditions were reached when temperatures were at their highest and OJP volcanism most intense. The latter part of OAE 1a was characterized by cooling events, probably promoted by CO2 sequestration via burial of organic matter (OM). The end of anoxia coincided with the cessation of volcanism and a marked cooling. The mid-Aptian was characterized by relatively high surface-water fertility and decreasing temperatures, probably resulting from intense weathering drawing down pCO2. The lowest temperatures and low fertility, were reached in the middle–late Aptian across the interval characterized by blooming of N. truittii. The data presented suggest that OJP played a direct role in inducing global warming during OAE 1a, whereas other mechanisms (weathering, deposition of OM) acted as feedback processes favoring temporary cooler interludes.
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