Abrupt conclusion of the late Miocene-early Pliocene biogenic bloom at 4.6-4.4 Ma

Abstract

The late Miocene-early Pliocene biogenic bloom was an extended time interval characterised by elevated ocean export productivity at numerous locations. As primary productivity is nutrient-limited at low-to-mid latitudes, this bloom has been attributed to an increase or a redistribution of available nutrients, potentially involving ocean-gateway or monsoon-related mechanisms. While the exact causal feedbacks remain debated, there is even less consensus on what caused the end of the biogenic bloom. Here, we compile Mio-Pliocene paleoproductivity proxy data from all major ocean basins to evaluate the timing and pacing of this termination. This systematic analysis reveals an abrupt and sustained reduction in low-latitude ocean productivity at 4.6–4.4 Ma. The decline in productivity coincided with a prolonged period of low orbital eccentricity and a shift towards lower-amplitude obliquity, an astronomical configuration linked to reduced East Asian Monsoon intensity and decreased riverine nutrient supply.

The History of Cenozoic Carbonate Flux in the Atlantic Ocean Constrained by Multiple Regional Carbonate Compensation Depth Reconstructions

“…The apparent absence of this event in the North Atlantic (Figure 3) may also reflect widespread downslope displacement of carbonate sediment into the deepest abyssal plains of the North Atlantic, introducing considerable scatter in CAR values with depth (Thiede et al, 1980). The termination of the biogenic bloom has been linked to reduced intensity of the East Asian Monsoon and an associated decrease in chemical weathering and nutrient supply (Karatsolis et al, 2022). The Quaternary CCD (∼2.5 Ma to present) displays a tightly constrained shallowing in the South Atlantic by ∼500 m. A similar shallowing is observed in the central North Atlantic which is less well constrained due to large uncertainties, while the shallowing is not seen in the northern North Atlantic (Figure 3).…”

The Late Miocene Biogenic Bloom : A globally distributed but not an ubiquitous event

“…Moreover, the nutrient input would be then restricted to areas downwind of the arid and desert regions which is not clearly the case in our records. Karatsolis et al (2022) suggest an end of the LMBB at 4.6-4.4 Ma related to a decrease in insolation which in turn would have caused a reduction in hydrological cycle intensity and continental weathering. Our compilation shows a significant decline in carbonate-related productivity in the Pacific Ocean at this time, although it does not appear to correspond to the end of the LMBB.…”

“…The authors attribute this shift to the final closure of the Central American Seaway that prevented surface currents from exchanging between the Atlantic and Pacific Oceans. More recently, Karatsolis et al (2022) link the end of the LMBB with a decrease in insolation due to a particular orbital configuration. This drop in insolation would have caused a reduction in hydrological cycle intensity and therefore a decrease in continental weathering and nutrient supply to the ocean.…”

“…In contrast to Karatsolis et al (2022) who choose to focus on high resolution records only, we here choose a less selective approach because even lower resolution datasets or datasets that show no signature of the LMBB can help us understand its origin. We compiled oceanographic data from DSDP, ODP and IODP expeditions that cover the late Miocene and early Pliocene.…”

Resolved and Redeemed: A New Fleck to the Evolutionary Divergence in the Genus Scomberomorus Lacepède, 1801 (Scombridae) With Cryptic Speciation

“…Furthermore, the diversification of S. aff. guttatus into three lineages in the Pliocene could be accelerated by the increase in productivity associated with the biogenic bloom, and shifts in monsoon activity occurred in the Miocene period in the Indian Ocean (Karatsolis et al, 2022). The superimposed climatic changes with local adaptations followed by reproductive aggregation possibly led to sympatric speciation in this genus (Qvarnström et al, 2016;Beal et al, 2020).…”