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Stable isotope studies of selected s...

Southern Methodist University., Geological Sciences.

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Stable isotope studies of selected synthetic and pedogenic hydroxyl-bearing minerals and some implications for the environment of the mid-Cretaceous.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Stable isotope studies of selected synthetic and pedogenic hydroxyl-bearing minerals and some implications for the environment of the mid-Cretaceous./
作者:	Feng, Weimin.
面頁冊數:	208 p.
附註:	Adviser: Crayton J. Yapp.
Contained By:	Dissertation Abstracts International70-05B.
標題:	Atmospheric Sciences. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoeng/servlet/advanced?query=3356139
ISBN:	9781109160116

Stable isotope studies of selected synthetic and pedogenic hydroxyl-bearing minerals and some implications for the environment of the mid-Cretaceous.
Feng, Weimin.

Stable isotope studies of selected synthetic and pedogenic hydroxyl-bearing minerals and some implications for the environment of the mid-Cretaceous. - 208 p.

Adviser: Crayton J. Yapp.

Thesis (Ph.D.)--Southern Methodist University, 2009.

Hydroxyl-bearing pedogenic minerals such as goethite, gibbsite and kaolinite are commonly formed in Earth's surface and near surface environments in the presence of meteoric waters. Their hydrogen and oxygen isotopic compositions (deltaD and delta18O, respectively) can be used as paleothermometers, while the concentrations and carbon isotopic compositions (delta13C) of the CO2 occluded in the structure of goethite and gibbsite can be an indicator of the ancient atmospheric PCO2.

ISBN: 9781109160116Subjects--Topical Terms:

1019179
Atmospheric Sciences.

Stable isotope studies of selected synthetic and pedogenic hydroxyl-bearing minerals and some implications for the environment of the mid-Cretaceous.
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245 1 0 $a Stable isotope studies of selected synthetic and pedogenic hydroxyl-bearing minerals and some implications for the environment of the mid-Cretaceous.
300 $a 208 p.
500 $a Adviser: Crayton J. Yapp.
500 $a Source: Dissertation Abstracts International, Volume: 70-05, Section: B, page: .
502 $a Thesis (Ph.D.)--Southern Methodist University, 2009.
520 $a Hydroxyl-bearing pedogenic minerals such as goethite, gibbsite and kaolinite are commonly formed in Earth's surface and near surface environments in the presence of meteoric waters. Their hydrogen and oxygen isotopic compositions (deltaD and delta18O, respectively) can be used as paleothermometers, while the concentrations and carbon isotopic compositions (delta13C) of the CO2 occluded in the structure of goethite and gibbsite can be an indicator of the ancient atmospheric PCO2.
520 $a Models suggest that naturally occurred, up to 33 mole % of, substitution of iron by aluminum in goethite structure may affect the isotopic fractionation factors between goethite and water, and lead to significant overestimation of the formation temperature when using goethite hydrogen-oxygen isotopic geothermometer. This effect was tested experimentally with synthetic goethite of different degrees of substitution of Al for Fe. The hydrogen isotopic compositions of the structural hydrogen (deltaDs) of synthetic goethites were determined and indicate an increase of the deltaDs value by about 1.4 (+/-0.4) &permil; for every 1 mole %of Al. This magnitude of impact is somewhat larger than the predictions from a published model. However, the overall uncertainties in the current results support the usage of previously adopted adjustment for goethite deltaDs values (subtracting ~1&permil; from measured deltaD values of Al-substituted goethite for each mole % of Al-substitution).
520 $a A mid-Cretaceous (~95 Ma) paleosol in southwestern Minnesota at a paleolatitude of 40°N provides an opportunity for obtaining continental paleoclimatic and paleoenvironmental information of one of the warmest periods in Earth's history. Two paleosol outcrops were studied, both contains primarily gibbsite, quartz, and kaolinite, while smaller amounts of goethite and hematite were found in one outcrop.
520 $a deltaD and delta18O values were determined for kaolinite in paleosol samples to be about - 72&permil;, and 18.3&permil;, respectively. Thus, a kaolinite hydrogen-oxygen isotopic geothermometer indicates a crystallization temperature of 24 +/- 4°C with a corresponding delta18O value of -6.4&permil; for the ancient water. This Cenomanian continental temperature (24°C) is significantly higher than modern local mean annual temperature (7°C), and is in general accord with published mid-Cretaceous paleotemperatures estimated from leaf margin analysis of continental plant fossils.
520 $a Despite the complication caused by apparent presence of more than one generation of goethites in hot 5 M NaOH treated paleosol samples. An ancient tropospheric CO2 concentration of ~1900 ppmV was determined from the measured delta13C values and concentrations of Fe(CO3)OH components in older generation of goethites. This inferred CO2 concentration is near the mid-point of the range reported for the mid-Cretaceous by workers using other CO2 proxies.
520 $a The correspondence of the temperature of 24°C at a mid-paleolatitude of ~40°N with the relatively high concentration of Cenomanian tropospheric CO2 (~1900 ppmV) is consistent with the idea that increase of atmospheric CO2 concentrations has a positive relation to global warming.
590 $a School code: 0210.
650 4 $a Atmospheric Sciences. $3 1019179
650 4 $a Geochemistry. $3 539092
650 4 $a Geology. $3 516570
690 $a 0372
690 $a 0725
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710 2 $a Southern Methodist University. $b Geological Sciences. $3 1019579
773 0 $t Dissertation Abstracts International $g 70-05B.
790 $a 0210
790 1 0 $a Gregory, Robert T. $e committee member
790 1 0 $a Maguire, John A. $e committee member
790 1 0 $a Tabor, Neil J. $e committee member
790 1 0 $a Walther, John V. $e committee member
790 1 0 $a Yapp, Crayton J., $e advisor
791 $a Ph.D.
792 $a 2009
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoeng/servlet/advanced?query=3356139