High School

The sketch above depicts different sedimentary environments labeled by letters a - e. Choose the order of rocks that would form in these environments from closest to farthest from the source.

1) Conglomerate, Sandstone, Shale, Limestone, Chert
2) Shale, Sandstone, Conglomerate, Limestone, Chert
3) Sandstone, Conglomerate, Shale, Chert, Limestone
4) Limestone, Chert, Shale, Sandstone, Conglomerate

Answer :

The correct sedimentary rock sequence from closest to farthest from the source is conglomerate, sandstone, shale, limestone, and chert, reflecting the increasing transport distance and degree of particle sorting.

The correct sequence of sedimentary rocks that would form in environments from closest to farthest from the source, given the options provided, is conglomerate, sandstone, shale, limestone, and chert. This order is a result of the sedimentary process where conglomerate forms in riverbed environments closest to the source material, wherein larger clasts like rounded pebbles are deposited.

As transportation agents like water move materials further from the source, they sort and round the particles more extensively, with sandstone settling in past beach or desert environments, followed by shale, which is made of even smaller clay particles and is characteristic of past lagoons or lakes. Given enough time and the right conditions, limestone, which is not a clastic rock but a biochemical sedimentary rock often indicates a shallow, warm oceanic environment, while chert, a type of chemical sedimentary rock, forms even further away and often in deeper oceanic environments.