Shackford, Julia K. and Lyle, Mitchell (2012): Eastern Equatorial Pacific CaCO (sub 3) dissolution during the mid-Miocene; a study using IODP peat cores

Leg/Site/Hole:
IODP 320
IODP 321
DSDP 85
DSDP 85 574
IODP 320 U1336
IODP 321 U1337
Identifier:
2013-047181
georefid

Creator:
Shackford, Julia K.
Texas A&M University, Department of Oceanography, College Station, TX, United States
author

Lyle, Mitchell
author

Identification:
Eastern Equatorial Pacific CaCO (sub 3) dissolution during the mid-Miocene; a study using IODP peat cores
2012
In: Anonymous, Geological Society of America, 2012 annual meeting
Geological Society of America (GSA), Boulder, CO, United States
44
7
122
X-ray Fluorescence (XRF) scan data from Integrated Ocean Drilling Program (IODP) Expedition 320/321 in the Eastern Equatorial Pacific show evidence of carbonate dissolution occurring at multiple times during the Cenozoic. These large-scale changes in the carbon cycle are reflected in changes of the carbonate compensation depth. We have identified a major carbonate dissolution cycle during the early to mid-Miocene ( approximately 18-16 Ma). Inadequate core recovery within the interval has hindered study of this 17 Ma dissolution event. IODP Expedition 320/321 (Pacific Equatorial Age Transect [PEAT]) recovered new, nearly continuous sediment records of the early Miocene allowing much more detailed study. XRF scan data from Sites U1335, U1336, and U1337 over the 18-16 Ma interval and XRF scan data from Deep Sea Drilling Program (DSDP) Site 574 are used to better define the timing and understanding of how productivity and changes in ocean carbon affected carbonate preservation in the sediments. The 17 Ma event lasted approximately 1 million years and is strongly influenced by orbital insolation changes. The CaCO (sub 3) analyses indicate cyclicity on an approximately 100,000 year time scale. Core sections from PEAT Sites U1335, U1336, and U1337, and DSDP Leg 85 Site 574 were analyzed at 2.0 to 2.5 cm intervals to provide elemental identification of sediment composition in the dissolution interval. Ca and Si are used to calculate biogenic carbonate and silica, while the majority of Ba is biogenic Ba, which is an effective proxy for productivity. Comparison of the different signals allows us to determine how the interval was affected by both productivity and dissolution. %C, %CaCO (sub 3) , %C (sub org) , and %Si analyses were completed in order to develop a calibration curve for the U1337 XRF data to approximate the amount of each of those components within the cores. We use all three of the IODP Leg 320/321 sites in the study to provide a matrix of sedimentation rates and latitude for the early Miocene. These sites were at roughly the same depth at 17 Ma, approximately 4 km, and formed a transect of paleolatitude from the equator, through 1 degrees N to 3.5 degrees N. Since the magnitude of productivity strongly depends on latitude in the equatorial Pacific, these three sites can be used to distinguish between productivity transients and dissolution events.
English
Coverage:Geographic coordinates:
North:7.4204
West:-133.1949East: -123.1222
South:3.5000

Stratigraphy; carbonate compensation depth; Cenozoic; Deep Sea Drilling Project; DSDP Site 574; East Pacific; eastern Equatorial Pacific; Equatorial Pacific; Expedition 320; Expedition 321; Expeditions 320/321; Integrated Ocean Drilling Program; IODP Site U1336; IODP Site U1337; IPOD; Leg 85; middle Miocene; Miocene; Neogene; North Pacific; Northeast Pacific; Pacific Ocean; paleo-oceanography; peat; sediments; Tertiary; X-ray analysis; X-ray fluorescence;

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