Terrestrial cosmogenic Be-10 dating of the Ultima Esperanza ice lobe moraines (52 degrees S, Patagonia) indicates the global Last Glacial Maximum (LGM) extent was half of the local LGM


ciner A., Sarıkaya M. A. , Yıldırım C., Girault I., Todisco D., Martin F., ...More

GEOMORPHOLOGY, vol.414, 2022 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 414
  • Publication Date: 2022
  • Doi Number: 10.1016/j.geomorph.2022.108381
  • Journal Name: GEOMORPHOLOGY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, PASCAL, Aerospace Database, Aquatic Science & Fisheries Abstracts (ASFA), CAB Abstracts, Communication Abstracts, Environment Index, Geobase, INSPEC, Metadex, Veterinary Science Database, DIALNET, Civil Engineering Abstracts
  • Keywords: Anibal Pinto moraine, Ultima Esperanza ice lobe, Patagonia, Cosmogenic surface exposure dating, Glacial asynchronicity, SOUTHERNMOST SOUTH-AMERICA, TORRES DEL PAINE, LATE PLEISTOCENE GLACIATIONS, ANTARCTIC PENINSULA REGION, NUCLIDE PRODUCTION-RATES, SIERRA-NEVADA, EXPOSURE AGES, ATMOSPHERIC CIRCULATION, QUATERNARY GLACIATION, CHILEAN PATAGONIA
  • Istanbul Technical University Affiliated: Yes

Abstract

Whether glaciers in the southern hemisphere were asynchronous to those in the north during the global Last Glacial Maximum (gLGM; 26.5-19 ka) is still debated. In Patagonia (South America), numerous ice lobes attained their maximum extents during diverse episodes of the last glacial cycle. To understand the variations in the gLGM vs local LGM record, we studied the Lago Anibal Pinto area (52 degrees 00' S, 72 degrees 40' E; Chile), where several moraine belts were deposited by one of the eastward-flowing southern Patagonian Ice Sheet (PIS) outlet ice lobes; the Ultima Esperanza. We report eight Be-10 terrestrial cosmogenic nuclides (TCN) surface ages from granitic moraine boulders. Our weighted average age obtained from the southern part of the Rio Turbio moraine belt yields 50.7 +/- 2.4 ka (oldest boulder age; 53.8 +/- 5.3 ka) and confirms the greatest extent of the local Last Glacial Maximum (lLGM) during Marine Isotope Stage 3 (MIS 3) in the previously dated northern moraines from the same belt. Our Be-10 TCN age (32.6 +/- 2.2 ka) derived from the Dos Lagunas moraine, which makes up the northernmost margin of the Ultima Esperanza ice lobe's Arauco advance, also validates the MIS 3 timing. Following the formation of Arauco moraines, the Ultima Esperanza ice lobe was split into three main tributaries in the south, which formed three restricted and previously undated moraine complexes. We dated one of them, the Anibal Pinto moraine complex. Whereas the highest moraine yielded the oldest age (28.3 +/- 2.2 ka), lower moraine's surface that was later truncated as a lacustrine erosional platform, yielded younger boulder ages (weighted average age = 18.9 +/- 1.0 ka; oldest boulder age = 19.0 +/- 1.5 ka), indicating they were deposited under the Pinto Lake level. Our new age data allow us to propose a new chronology for the Anibal Pinto moraine complex and consolidate previously published ages from other moraine belts. We attribute the Anibal Pinto moraine complex to early gLGM (MIS 2), emphasising that the gLGM was half the extent of lLGM in the Ultima Esperanza ice lobe that underpins its interhemispheric asynchronous character.