Aeolianite, calcrete/microbialite and karst in southwestern Australia as indicators of Middle to Late Quaternary palaeoclimates

作者：Lipar Matej^*; Webb John A; Cupper Matthew L; Wang Ningsheng

来源：Palaeogeography, Palaeoclimatology, Palaeoecology, 2017, 470: 11-29.

DOI：10.1016/j.palaeo.2016.12.019

• Tamala limestone
• Pleistocene
• Holocene
• Calcarenite
• Glacial period
• Interglacial period

The mid-Late Pleistocene and Holocene aeolianites of the Tamala Limestone on the northern Swan Coastal Plain in southwestern Western Australia consist of six members that show cyclic deposition of coastal aeolianite, overlain by calcrete/microbialite, karstified surface and palaeosol. Field work, combined with mineralogical, chemical, stable isotope analysis and uranium-thorium (Uffh) and optically stimulated luminescence (OSL) dating, provides an insight into the repetitive glacial and interglacial climatic periods over the past 500 kyr. Deposition of the carbonate aeolianites occurred during interglacial episodes (marine isotope stage (MIS) 1, 5, 7, 9,11, and possibly 13), due to migration of coastal dunes under the influence of strong southerly to southwesterly winds. Rainfall was insufficient to support vegetation cover on the dunes, and so was probably limited or seasonal. The transition from interglacial to glacial climates was characterised by higher effective rainfall, accompanied by aeolianite dissolution and karstification. During the colder climates and less effective rainfall of the glacial periods, there was no carbonate sand deposition; instead laminated microbialite and/or laminar calcrete formed, followed by palaeosol formation. The oxygen isotope composition of the microbialites indicates average temperatures during glacial periods similar to 4 degrees C -8 degrees C lower than today, and delta C-13 values demonstrate a higher proportion of C4 plants and therefore a drier or more seasonal climate. Data from individual members of the Tamala Limestone show that the wettest interglacial period was MIS 5, when extensive karstification and pinnacle development occurred, and rainfall was probably higher than at any other time in the past 500 kyr. Of the glacial periods, MIS 10 was relatively wet or less seasonal, whereas MIS 8 and the Last Glacial Maximum (LGM) were relatively dry and windy. The low rainfall during the peak of the glacial periods was probably intensified by colder water offshore, due to weakening of the Leeuwin Current and its replacement by the cold, north-flowing West Australian Current.

• 出版日期2017-3-15