scholarly journals Paleoenvironmental conditions for the development of calcareous nannofossil acme during the late Miocene in the eastern equatorial Pacific

2014 ◽  
Vol 29 (3) ◽  
pp. 210-222 ◽  
Author(s):  
Catherine Beltran ◽  
Gabrielle Rousselle ◽  
Jan Backman ◽  
Bridget S. Wade ◽  
Marie Alexandrine Sicre
Keyword(s):  
Late Miocene ◽  
Equatorial Pacific ◽  
Calcareous Nannofossil ◽  
Eastern Equatorial Pacific

scholarly journals Late Miocene calcareous nannofossil genus <i>Catinaster:</i> taxonomy, evolution and magnetobiochronology

1998 ◽  
Vol 17 (1) ◽  
pp. 71-85 ◽  
Author(s):  
Alyssa Peleo-Alampay ◽  
David Bukry ◽  
Li Liu ◽  
Jeremy R. Young
Keyword(s):  
Indian Ocean ◽  
Gulf Of Mexico ◽  
Systematic Study ◽  
Late Miocene ◽  
Equatorial Pacific ◽  
Calcareous Nannofossil ◽  
New Subspecies ◽  
Eastern Equatorial Pacific ◽  
First Occurrence ◽  
The Indian Ocean

Abstract. A systematic study on the evolution and stratigraphic distribution of the species of Catinaster from several DSDP/ODP sites with magnetostratigraphic records is presented. The evolution of Catinaster from Discoaster is established by documentation of a transitional nannofossil species, Discoaster transitus. Two new subspecies, Catinaster coalitus extensus and Catinaster calyculus rectus are defined which appear to be intermediates in the evolution of Catinaster coalitus coalitus to Catinaster calyculus calyculus. The first occurrence of C. coalitus is shown to be in the lower part of C5n.2n at 10.7–10.9 Ma in the low to mid–latitude Atlantic and Pacific Oceans. The last occurrence of C. coalitus coalitus varies from the upper part of C5n.2n to the lower portion of C4A. Magnetobiostratigraphic evidence suggests that the FO of C. calyculus rectus is diachronous. Catinaster mexicanus occurs in the late Miocene and has been found only in the eastern equatorial Pacific, the Indian Ocean and the Gulf of Mexico.

scholarly journals Eastern equatorial Pacific cold tongue evolution since the late Miocene linked to extratropical climate

2019 ◽  
Vol 5 (4) ◽  
pp. eaau6060 ◽  
Author(s):  
Jingjing Liu ◽  
Jun Tian ◽  
Zhonghui Liu ◽  
Timothy D. Herbert ◽  
Alexey V. Fedorov ◽  
...  
Keyword(s):  
Late Miocene ◽  
Salient Feature ◽  
Warm Pool ◽  
Equatorial Pacific ◽  
Cold Tongue ◽  
Geological Time ◽  
Tropical Ocean ◽  
Temperature Changes ◽  
Eastern Equatorial Pacific ◽  
Pacific Warm Pool

The timing and mechanisms of the eastern equatorial Pacific (EEP) cold tongue development, a salient feature of the tropical ocean, are intensely debated on geological time scales. Here, we reconstruct cold tongue evolution over the past 8 million years by computing changes in temperature gradient between the cold tongue and eastern Pacific warm pool. Results indicate that the cold tongue remained very weak between 8 and 4.3 million years ago, implying much weaker zonal temperature gradients prevailing during the late Miocene–Pliocene, but then underwent gradual intensification with apparently increasing sensitivity of the cold tongue to extratropical temperature changes. Our results reveal that the EEP cold tongue intensification was mainly controlled by extratropical climate.

scholarly journals Late Miocene to Holocene high-resolution eastern equatorial Pacific carbonate records: stratigraphy linked by dissolution and paleoproductivity

2019 ◽  
Vol 15 (5) ◽  
pp. 1715-1739 ◽  
Author(s):  
Mitchell Lyle ◽  
Anna Joy Drury ◽  
Jun Tian ◽  
Roy Wilkens ◽  
Thomas Westerhold
Keyword(s):  
High Resolution ◽  
Primary Production ◽  
Late Miocene ◽  
Equatorial Pacific ◽  
Ocean Drilling Program ◽  
Regional Patterns ◽  
Ocean Drilling ◽  
Eastern Equatorial Pacific ◽  
Compensation Depth ◽  
Carbonate Compensation Depth

Abstract. Coherent variation in CaCO3 burial is a feature of the Cenozoic eastern equatorial Pacific. Nevertheless, there has been a long-standing ambiguity in whether changes in CaCO3 dissolution or changes in equatorial primary production might cause the variability. Since productivity and dissolution leave distinctive regional signals, a regional synthesis of data using updated age models and high-resolution stratigraphic correlation is an important constraint to distinguish between dissolution and production as factors that cause low CaCO3. Furthermore, the new chronostratigraphy is an important foundation for future paleoceanographic studies. The ability to distinguish between primary production and dissolution is also important to establish a regional carbonate compensation depth (CCD). We report late Miocene to Holocene time series of XRF-derived (X-ray fluorescence) bulk sediment composition and mass accumulation rates (MARs) from eastern equatorial Pacific Integrated Ocean Drilling Program (IODP) sites U1335, U1337, and U1338 and Ocean Drilling Program (ODP) site 849, and we also report bulk-density-derived CaCO3 MARs at ODP sites 848, 850, and 851. We use physical properties, XRF bulk chemical scans, and images along with available chronostratigraphy to intercorrelate records in depth space. We then apply a new equatorial Pacific age model to create correlated age records for the last 8 Myr with resolutions of 1–2 kyr. Large magnitude changes in CaCO3 and bio-SiO2 (biogenic opal) MARs occurred within that time period but clay deposition has remained relatively constant, indicating that changes in Fe deposition from dust is only a secondary feedback to equatorial productivity. Because clay deposition is relatively constant, ratios of CaCO3 % or biogenic SiO2 % to clay emulate changes in biogenic MAR. We define five major Pliocene–Pleistocene low CaCO3 % (PPLC) intervals since 5.3 Ma. Two were caused primarily by high bio-SiO2 burial that diluted CaCO3 (PPLC-2, 1685–2135 ka, and PPLC-5, 4465–4737 ka), while three were caused by enhanced dissolution of CaCO3 (PPLC-1, 51–402 ka, PPLC-3, 2248–2684 ka, and PPLC-4, 2915–4093 ka). Regional patterns of CaCO3 % minima can distinguish between low CaCO3 caused by high diatom bio-SiO2 dilution versus lows caused by high CaCO3 dissolution. CaCO3 dissolution can be confirmed through scanning XRF measurements of Ba. High diatom production causes lowest CaCO3 % within the equatorial high productivity zone, while higher dissolution causes lowest CaCO3 percent at higher latitudes where CaCO3 production is lower. The two diatom production intervals, PPLC-2 and PPLC-5, have different geographic footprints from each other because of regional changes in eastern Pacific nutrient storage after the closure of the Central American Seaway. Because of the regional variability in carbonate production and sedimentation, the carbonate compensation depth (CCD) approach is only useful to examine large changes in CaCO3 dissolution.

scholarly journals New data on the stratigraphic distribution of the nannofossil genus <i>Catinaster</i> and on evolutionary relationships among its species

2013 ◽  
Vol 32 (2) ◽  
pp. 197-205 ◽  
Author(s):  
Marina Ciummelli ◽  
Isabella Raffi
Keyword(s):  
Late Miocene ◽  
Short Interval ◽  
Evolutionary Relationships ◽  
Calcareous Nannofossil ◽  
Equatorial Atlantic ◽  
Eastern Equatorial Pacific ◽  
C 50 ◽  
Evolutionary Emergence ◽  
Early Late ◽  
The Tropical Pacific

Abstract. Examination of Upper Miocene–Lower Pliocene sediments at IODP Site U1338, in the Eastern Equatorial Pacific, provided new data on the distribution range of the calcareous nannofossil genus Catinaster. In addition to the the well-known occurrence of Catinaster coalitus and Catinaster calyculus in the early Late Miocene, we document Catinaster mexicanus in both the mid-late Miocene and the Early Pliocene. We confirm its taxonomic validity, rejecting previous interpretations of Pliocene C. mexicanus specimens as the result of dissolution of Discoaster altus. Instead, the Pliocene appearance of C. mexicanus seems to originate from the D. altus lineage. The short interval of occurrence (c. 50 ka) in the Late Miocene may document a preliminary evolutionary emergence of C. mexicanus that lacks any relationship with the other Catinaster species. Clear ancestor species to validate its independent origin from Discoaster are, however, missing. In the stratigraphic intervals where Catinaster species are found, their co-occurrence with Discoaster species bearing a prominent star-shaped boss on one side is noteworthy. This suggests that Catinaster and Discoaster at times developed a common morphological feature (a stellate structure, with or without hexaradiate symmetry), possibly under recurrent changes in climatic/environmental conditions. The data presented on C. mexicanus suggest a wider geographical distribution than previously thought, extending from the tropical Pacific to the Gulf of Mexico, equatorial Atlantic and tropical Indian oceans.

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