Publication Date:
2022-03-17
Description:
A high resolution study of calcareous nannofossils has been performed on samples from the Sapropel S1interval
deposited in the North Ionian Sea, with the aim to assess the paleoenvironmental changes in the photic zone
during this crucial interval in Mediterranean circulation. Calcareous nannofossil data have been integrated with
planktonic foraminiferal data recently published from which the paleoclimatic curve has been constructed.
Placoliths (namely Emiliania huxleyi) and Florisphaera profunda distributions, along with that of planktonic
foraminifer Globigerinoides ruber white, evidence that, after a progressive weakening of surface water mixing, a
deep chlorophyll maximum developed just prior to the sapropel deposition. We suggest that these changes took
place as a response to enhanced precipitation conditions and riverine discharge as testified by increasing trend of
reworked coccoliths and the occurrence of lower salinity taxon Braarudosphaera bigelowii. Calcareous nannofossils
also point out that the oceanographic (water column stratification, reduced bottom water ventilation) and
biogeochemical (increased primary production) processes that occurred during the S1 formation were particularly
dominant during the earliest part of the older S1 warm phase (S1a). Our results support than some reventilation
events of the shallow depth of studied site (665 m) occurred to some extent, particularly during
the final phases of S1a.
The distribution of holococcoliths, more abundant during the cold interruption phase S1i, seems confirm that
the preservation of these tiny and delicate coccoliths, highly susceptible to dissolution, is enhanced under seafloor
re-ventilation conditions.
Finally, we tentatively suggest that preservation also plays a significant role in the distribution of the warm
upper photic zone taxa, particularly during the warm S1b interval.
Description:
Published
Description:
103599
Description:
4A. Oceanografia e clima
Description:
JCR Journal
Keywords:
Sapropel S1
;
Calcareous nannofossils
;
Planktonic foraminifera
;
North Ionian Sea
;
Mediterranean
;
Hydrosphere
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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