菜鸟请教OG11 2

Of all the vast tides of migration that swept through history, maybe none is more concentrated as the wave that brought 12 million immigrants onto American shores in little more than 3 decades.

问题如下：

1、句首of 是否可替换成其他介词如during？

2、句中的in little more than 3 decades 不太理解其意思和句式结构？

请诸位高手不吝赐教~

in是和后面3decades一起的

more than 修饰 3 decades

而 little 修饰 比较级