Millennial scale climate cycles in Permian-Carboniferous rhythmites; permanent feature throughout geologic time?
Millennial scale climate cycles in Permian-Carboniferous rhythmites; permanent feature throughout geologic time?
Geology (Boulder) (November 2011) 40 (1): 19-22
- basin analysis
- basins
- Brazil
- Carboniferous
- Cenozoic
- characteristic remanent magnetization
- clastic rocks
- cyclic processes
- depositional environment
- geochronology
- glacial sedimentation
- Holocene
- Itarare Subgroup
- magnetic properties
- magnetic susceptibility
- magnetization
- Milankovitch theory
- paleoclimatology
- paleoenvironment
- paleomagnetism
- Paleozoic
- Parana Basin
- Parana Brazil
- periodicity
- Permian
- planar bedding structures
- Quaternary
- relative age
- remanent magnetization
- rhythmite
- sedimentary basins
- sedimentary rocks
- sedimentary structures
- sedimentation
- South America
- Bond cycles
Two late Paleozoic glacial rhythmite successions from the Itarare Group (Parana Basin, Brazil) were examined for paleoclimate variations. Paleomagnetic (characteristic remanent magnetization, ChRM) and magnetic susceptibility (K (sub z) ) measurements taken from the rhythmites are interpreted as paleoclimatic proxies. Ratios of low-frequency components in the K (sub z) variations suggest Milankovitch periodicities; this leads to recognition of other, millennial-scale variations reminiscent of abrupt climate changes during late Quaternary time, and are suggestive of Bond cycles and the 2.4 k.y. solar cycle. We infer from these patterns that millennial-scale climate change is not restricted to the Quaternary Period, and that millennial forcing mechanisms may have been prevalent throughout geologic time.
