叠: Ⅰ动词1.(一层加上一层; 重复) pile up; repeat 短语和例子层峦叠嶂 peaks rising one higher than another; 一个一个往上叠 pile one above another2.(折叠) fold 短语和例子把信叠好 fold the letter; 叠被子 fold up a quilt; 这些轻便折椅可以叠起来放进汽车。
The second terrace turned into a complex terrace because of the slackwater sediments caused by the yellow river ' s flood in late holocene 距今4000年左右的史前洪水阶地上加积了一层平流沉积物，形成复合型阶地，其下部为基座阶地，上部为上叠阶地。
