The Rio Grande do Sul coastal plain in southern Brazil holds important clues about past climate changes. Sediments there show evidence of sea-level changes over the last 400,000 years. The area has two main types of sediment deposits - one from nearby rocks and another from barrier-lagoon systems. These systems formed as sea levels rose and fell, creating distinct layers in the landscape. The sediments in this region provide a valuable record of how the environment has changed over time.