Hunting down the late Miocene-early Pliocene biogenic bloom in the Tasman Sea: an integrated study at IODP Site U1506

2021 ◽  
Author(s):  
Maria Elena Gastaldello ◽  
Claudia Agnini ◽  
Edoardo Dallanave ◽  
Thomas Westerhold ◽  
Adriane R. Lam ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Late Miocene ◽  
Integrated Approach ◽  
Marine Geology ◽  
Calcareous Nannofossils ◽  
Low Oxygen ◽  
Precise Position ◽  
Early Pliocene ◽  
Tasman Sea ◽  
Integrated Study

<p>The latest Miocene-early Pliocene biogenic bloom is a poorly understood paleoceanographic event that has been traditionally related to increased primary productivity; and associated changes in the marine carbon cycle. In order to identify this event in the Tasman Sea, we carried out an integrated study at IODP Site U1506. First, we have constructed an age model based on an integrated approach (i.e. biostratigraphy, astrocyclostratigraphic tuning). This permits the identification of the precise position as well as the duration of the biogenic bloom in the Tasman Sea but also the calculation of sedimentation rates across the study interval. In this framework, we generated quantitative micropaleontological records (benthic and planktic foraminifera and calcareous nannofossils) and a low-resolution carbon and oxygen stable isotope records on <em>Cibicidoides mundulus</em> and <em>Trilobatus sacculifer</em> across an interval spanning from 233.50 to 81.75 m CSF-A (Tortonian, late Miocene to Zanclean, early Pliocene). Quantitative assemblage work and statistical analyses on the resulting dataset point to increased export productivity in the lower part of the interval (between CNM15 and CNM18, Backman et al., 2012), as inferred from benthic foraminiferal assemblages dominated by taxa (e.g. <em>Uvigerina</em> and <em>Ehrenbergina</em>) that have been reported to be common across the biogenic bloom in the Indian Ocean (Dickens and Owen, 1999). The paleoecological analysis of these assemblages suggests eutrophic conditions at the seafloor and low oxygen concentration of bottom waters.</p><p><strong>Reference</strong></p><p>Backman, J., Raffi, I., Rio, D., Fornaciari, E., & Pälike, H., 2012. Biozonation and biochronology of Miocene through Pleistocene calcareous nannofossils from low and middle latitudes. Newsletters on Stratigraphy, 45(3), 221–244.</p><p>Dickens, G.R. and Owen, R.M., 1999. The latest Miocene-early Pliocene biogenic bloom: A revised Indian Ocean perspective. Marine Geology, 161: 75-91.</p><p><strong>Acknowledgments</strong></p><p>University of Padova DOR grant, CARIPARO Foundation Phd scholarship.</p><p>Spanish Ministry of Economy and Competitiveness and FEDER funds (PID2019-105537RB-I00).<strong> </strong></p>

Geochemical and Geophysical Evidence for Late Miocene Onset of Tasman Leakage

2020 ◽  
Author(s):  
Beth Christensen ◽  
David DeVleeschouwer ◽  
Jeroen Groeneveld ◽  
Jorijntje Henderiks ◽  
Gerald Auer ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Southern Hemisphere ◽  
Ocean Circulation ◽  
Late Miocene ◽  
Return Flow ◽  
Intermediate Water ◽  
Isotope Data ◽  
The North ◽  
Tasman Sea ◽  
Intermediate Waters

<p>The recent documentation of the southern hemisphere “supergyre”, the coupled subtropical southern hemisphere gyres spanning the 3 ocean basins, leads to questions about its impact on Indian Ocean circulation. The Indonesian Throughflow (ITF) acts as a switchboard directing warm surface waters towards the Agulhas Current (AC) and return flow to the North Atlantic, but Tasman Leakage (TL) is another source of return flow, however, at intermediate water depths. Fed by a complex mixture of South Pacific (SP) western boundary current surface and intermediate waters, and Antarctic Intermediate Water (AAIW), today the topography forces it to flow in a westerly direction. The TL flows over the Broken Ridge towards Madagascar, joining the AC and ultimately Atlantic Meridional Circulation (AMOC).</p><p>Stable isotope data from 4 DSPD/ ODP Indian Ocean sites define the history of TL and constrain the timing of its onset to ~7 Ma.  A simple nannofossil- biostratigraphy age model applied to previously published benthic foraminiferal carbon isotope data ensures the 4 time-series (~11 – 2 Ma) are consistent. All 4 records (Sites 752 Broken Ridge, 590 Tasman Sea, 757 90 East Ridge, 751 Kerguelen Plateau) are similar from ~11 Ma to ~7 Ma, indicating the Tasman Sea intermediate water was sourced from the Southern Ocean (SO). A coeval shift at ~7 Ma at Sites 590 and 752 signals a SP contribution and the onset of TL. We do not observe TL at Sites 757 and 751 and so interpret the post-7 Ma divergence between the TL pair and the KP / 90E Ridge sites as a reflection of different intermediate water masses. The KP / 90E Ridge sites record a more fully SO signal, and these waters are constrained to the region west of the 90 East ridge.</p><p>The isotopic record of TL onset suggests important tectonic changes ~ 7 Ma: 1) opening of the Tasman Sea to the north and 2) Australia’s northward motion allowing westward flow around Tasmania. The former is supported by a change in sedimentation style on the Marion Plateau (ODP Site 1197). The latter is supported by unconformities on the South Australian Bight margin (Leg 182 Sites 1126 (784 m), 1134 (701 m), 1130 (488m) and coeval decreases in mud- sized sediments at the Broken Ridge sites, indicating winnowing associated with the onset of the TL. A divergence is also apparent between Broken Ridge and Mascarene Plateau Site 707 records at this time. These events, coupled with the temporal relationship between the onset of the TL and a change in the character of deposition in the Maldives indicate enhanced Indian Ocean circulation at intermediate depths coincident with the late Miocene global cooling. Combined, these observations suggest the Indian Ocean in general plays a larger role in the global ocean system than previously recognized, and intermediate waters in particular are a critical yet poorly understood component of AMOC.</p>

scholarly journals High-Resolution Biostratigraphic Studies of Step-1 Well, Offshore, Western Niger Delta

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
M. E. Nton ◽  
S. O. Famori
Keyword(s):  
High Resolution ◽  
Late Miocene ◽  
Niger Delta ◽  
Calcareous Nannofossils ◽  
Early Pliocene ◽  
Sequence Stratigraphic ◽  
Foraminiferal Species ◽  
Stratigraphic Model ◽  
Niger Delta Basin ◽  
Preparation Techniques

Abstract A high-resolution biostratigraphic study of the STEP-1 well, offshore Western Niger Delta Basin, Nigeria, was carried out using foraminifera, calcareous nannofossils and palynomorphs. The study was aimed at identifying the biostratigraphic zones, age deductions as well as palaeoenvironmental and palaeoclimatic reconstructions. From the studied well section of 609 m (1,829–2,438 m), 50 ditch cuttings were used for foraminifera and calcareous nannofossils, while 25 samples were used for palynological studies at 12 m and 24 m intervals, respectively. Standard laboratory preparation techniques were employed for the three microfossil groups. Due to the occurrence of some forms such as Globigerina praebulloides, Haplophragmoides spp, Bolivina scalprata miocenica, Valvulina flexilis and Cyclammina cf. minima, two planktonic and one benthonic foraminifera zones were identified as follows: Lower N18, Upper N17 zone (early Pliocene, late Pliocene) and Cyclammina minima zone (late Miocene), respectively. Two biozones were recognized for the nannofossils and include NN12 (Ceratolithus cristatus zone) and NN11 (Discoaster berggrenii zone). These zones were assigned to early Pliocene and late Miocene, respectively. Other forms include Discoaster pentaradiatus, Sphenolithus abies and Ceratolithus armatus. Echitricolporites spinosus/P800zone has been assigned for the Palynomorph assemblages and was dated late Miocene due to the quantitative occurrence of Cyperaceaepollis spp. Four identified major condensed sections include intervals at 1,926, 1,987, 2,097 and 2,316 m, which have been dated 5.0, 5.8, 6.3 and 7.0 Ma, respectively. Based on the benthonic foraminiferal species and Palynological Marine Index, a shallow marine environment is deduced for the studied interval which was interpreted to be deposited under both wet and dry palaeoclimatic conditions. The findings, no doubt could serve as a template for a sequence stratigraphic model, generally beyond the resolution of seismic stratigraphy.

scholarly journals Landslide Susceptibility Assessment of Mauritius Island (Indian Ocean)

Geosciences ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 493 ◽  
Author(s):  
Vincenzo Marsala ◽  
Alberto Galli ◽  
Giorgio Paglia ◽  
Enrico Miccadei
Keyword(s):  
Indian Ocean ◽  
Landslide Susceptibility ◽  
Integrated Approach ◽  
Geographical Information ◽  
Susceptibility Assessment ◽  
Gis Technology ◽  
Mountain Areas ◽  
Landslide Susceptibility Assessment ◽  
Hydrological Hazards ◽  
Mauritius Island

This work is focused on the landslide susceptibility assessment, applied to Mauritius Island. The study area is a volcanic island located in the western part of the Indian Ocean and it is characterized by a plateau-like morphology interrupted by three rugged mountain areas. The island is severely affected by geo-hydrological hazards, generally triggered by tropical storms and cyclones. The landslide susceptibility analysis was performed through an integrated approach based on morphometric analysis and preliminary Geographical Information System (GIS)-based techniques, supported by photogeological analysis and geomorphological field mapping. The analysis was completed following a mixed heuristic and statistical approach, integrated using GIS technology. This approach led to the identification of eight landslide controlling factors. Hence, each factor was evaluated by assigning appropriate expert-based weights and analyzed for the construction of thematic maps. Finally, all the collected data were mapped through a cartographic overlay process in order to realize a new zonation of landslide susceptibility. The resulting map was grouped into four landslide susceptibility classes: low, medium, high, and very high. This work provides a scientific basis that could be effectively applied in other tropical areas showing similar climatic and geomorphological features, in order to develop sustainable territorial planning, emergency management, and loss-reduction measures.

Paleoenvironmental evolution of the East Carpathian foredeep during the late Miocene–early Pliocene (Dacian Basin; Romania)

2013 ◽  
Vol 103 ◽  
pp. 135-148 ◽  
Author(s):  
M. Stoica ◽  
I. Lazăr ◽  
W. Krijgsman ◽  
I. Vasiliev ◽  
D. Jipa ◽  
...  
Keyword(s):  
Late Miocene ◽  
Early Pliocene ◽  
Carpathian Foredeep ◽  
Paleoenvironmental Evolution
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