Review of the Early–Middle Pleistocene boundary and Marine Isotope Stage 19

Abstract

The Global Boundary Stratotype Section and Point (GSSP) defining the base of the Chibanian Stage and Middle Pleistocene Subseries at the Chiba section, Japan, was ratified on January 17, 2020. Although this completed a process initiated by the International Union for Quaternary Research in 1973, the term Middle Pleistocene had been in use since the 1860s. The Chiba GSSP occurs immediately below the top of Marine Isotope Substage (MIS) 19c and has an astronomical age of 774.1 ka. The Matuyama–Brunhes paleomagnetic reversal has a directional midpoint just 1.1 m above the GSSP and serves as the primary guide to the boundary. This reversal lies within the Early–Middle Pleistocene transition and has long been favoured to mark the base of the Middle Pleistocene. MIS 19 occurs within an interval of low-amplitude orbital eccentricity and was triggered by an obliquity cycle. It spans two insolation peaks resulting from precession minima and has a duration of ~ 28 to 33 kyr. MIS 19c begins ~ 791–787.5 ka, includes full interglacial conditions which lasted for ~ 8–12.5 kyr, and ends with glacial inception at ~ 774–777 ka. This inception has left an array of climatostratigraphic signals close to the Early–Middle Pleistocene boundary. MIS 19b–a contains a series of three or four interstadials often with rectangular-shaped waveforms and marked by abrupt (< 200 year) transitions. Intervening stadials including the inception of glaciation are linked to the calving of ice sheets into the northern North Atlantic and consequent disruption of the Atlantic meridional overturning circulation (AMOC), which by means of the thermal bipolar seesaw caused phase-lagged warming events in the Antarctic. The coherence of stadial–interstadial oscillations during MIS 19b–a across the Asian–Pacific and North Atlantic–Mediterranean realms suggests AMOC-originated shifts in the Intertropical Convergence Zone and pacing by equatorial insolation forcing. Low-latitude monsoon dynamics appear to have amplified responses regionally although high-latitude teleconnections may also have played a role.

Preface for the article collection “Stratigraphy and paleoclimatic/paleoenvironmental evolution across the Early–Middle Pleistocene transition in the Chiba composite section, Japan, and other reference sections in East Asia”

“…Because the Subarctic Front is presently situated just east of the Boso Peninsula (Qiu 2001), the Chiba composite section is located at an ideal position to record the past displacement of the front. Changes in marine microfossil assemblages and indicator taxa along with foraminiferal isotope data reveal millennial-scale fluctuations superimposed on glacial-interglacial orbital-scale variability, in which the phenomenon is generally coherent with detailed records from the North Atlantic and Mediterranean region (Haneda et al 2020b;Head 2021). Based on the abundant occurrences of a warm-water calcareous nannofossil and radiolarian species, Kameo et al (2020) and Itaki et al (2022) respectively show periodic intensifications of the Kuroshio Current following the end of MIS 19c and continuing into MIS 18, indicating repeated northward shifts of the Subarctic Front.…”

“…The Chiba composite section, including the Chiba section itself which was recently ratified as the Global Boundary Stratotype Section and Point (GSSP) defining the base of the Middle Pleistocene Subseries/Subepoch and Chibanian Stage/Age (Head 2021;Head et al 2021;Suganuma et al 2021), is a continuous marine silty sedimentary record from upper Marine Isotope Stage (MIS) 20 to lower MIS 18, representing one of the most expanded and chronostratigraphically constrained sections yet documented across the Lower-Middle Pleistocene boundary (e.g., Kazaoka et al 2015;Suganuma et al 2018). This composite section comprises five individual exposures cropping out along a 7.4 km transect, all securely linked by a detailed framework of tephra beds.…”

“…Both interglacials are characterized by low orbital eccentricity, and their precession and obliquity parameters are nearly in phase allowing their inception to be unambiguously aligned. For this reason, MIS 19c has been used as a baseline to understand the trajectory of our future interglacial under natural conditions (e.g., Tzedakis et al 2012;Suganuma et al 2018;Head 2021). Detailed paleoclimatic records of MIS 19 are therefore particularly significant.…”

“…Detailed paleoclimatic records of MIS 19 are therefore particularly significant. With this in mind, Head (2021) in this issue reviews the climatic characteristics of MIS 19 on a global scale, incorporating records from East Asia with other key sites from the Mediterranean and North Atlantic Ocean. A critical feature of MIS 19 is its pronounced millennial-scale climate variability following the inception of glaciation that terminates MIS 19c.…”

Millennial-scale oscillations in the Kuroshio–Oyashio boundary during MIS 19 based on the radiolarian record from the Chiba composite section, central Japan

“…Although this orbital configuration is similar to MIS 11 and the present interglacial (MIS 1), only MIS 19 and 1 show an obliquity peak and the precession minimum in-phase (Tzedakis 2010). Therefore, it is important to obtain a detailed understanding of the climatic features of this period, as doing so could provide insights for establishing a natural baseline for assessing future climate changes (e.g., Tzedakis et al 2012;Giaccio et al 2015;Sánchez Goñi et al 2016;Suganuma et al 2018;Head 2021).…”