中文摘要：

澳大利亚维多利亚州南部海岸坎贝尔港（Port Campbell）附近的十二门徒（The Twelve Apostles）地层主要为石灰质地层，偶见海相生物贝壳，一直被认为是浅海大陆架石灰岩（limestone）沉积。野外考察发现，该地层不仅存在海相生物碎片，同时也存在根化石、钙结核层等地表古土壤特征。为了更好地分析其沉积环境，本文对十二门徒剖面样品的粒度、石英颗粒表面形态以及稀土元素进行了系统分析，并将其结果与第四纪西峰黄土古土壤和现代海滩砂进行比较。结果表明，整个剖面序列以细粉砂为主，与典型风积黄土古土壤具有相似的粒度分布与粒度象特征，Sahu判别分析结果表明绝大部分样品值都小于-2.7411，显示了剖面整体以风积成因为主。样品的石英颗粒呈现出不规则的棱角状、次棱角状，显示风成特征；此外，十二门徒剖面样品具有与黄土古土壤以及上地壳（UCC）相似的稀土元素分配模式。因此，我们认为该地层并非海相石灰岩沉积，而是一套在半干旱气候条件下发育的具有多层钙结核的风积序列地层。该地层记录了澳洲东南海岸16.0-5.3Ma以来的风积历史与气候变化，表明澳大利亚的干旱化至少是在16Ma前就开始了。由于这套风积地层靠近海岸，易受地质时期海平面变化的影响，以致在地层中的局部层位出现海相生物碎屑，但地层的物质来源可能来源于澳大利亚的艾尔湖（Lake Eyre）盆地。

英文摘要：

The Twelve Apostles as a well known landmark, were 12 residual sea stacks, located in the Port Campbell National Park, south coast of Victoria, Australia. The stratum of these sea stacks and surrounding coastal cliffs are generally believed to be marine limestone deposited continental shelf since the Tertiary Period. They indeed show weathering characteristics of karst, such as stalactite, stalagmite and clint in some locations. However, such karst features are found to be formed during secondary weathering, as they are hardly to be followed along their bedding. Furthermore, aeolian pedogenic features are observed from this deposition, such as：（1）Many CaCO3 nodules were deposited underneath these beds; （2）Plant root fossils are commonly found in such beds; （3）Some beds are tilted to follow paleotopography, indicating their original topsoil position. In order to understand the origin of Port Campbell Limestone, one section from the Twelve Apostles（143°05＇21＂E, 38°39＇57＂S） was selected to study. The thickness of the section is 50m and 220 samples were totally collected from the top to 50m of the section, sampling intervals are 10cm in upper section（from 0m to 8m）and 30cm in lower section（from 8m to 50m）. Particle size, morphology of quartz grains, Rare Earth Elements（REE）were measured and compared with those of typical Quaternary aeolian loess-palaeosols and modern beach sand. The particles size of the whole section shows uniform fine feature and smaller than 100 μm. Silt fractions of Port Campbell Limestone are constantly dominant with the median grain size varying from 3.014 μm to 20.702 μm. Its particle characteristics of Port Campbell Limestone differs from those of modern beach sand, however are very close to those of loess and palaeosols according to Sahu＇s empirical judgement equation（the Y-values of eolian deposits using the equation should be smaller than -2.7411）. Scanning Electron Microscopy（SEM）analysis demonstrations that most of the quartz grains fr