What is the term used to describe the oldest and stable part located in the upper mantle of the earth?

The term that identifies the oldest and most stable part of the Earth's upper mantle is "Craton." Cratons are large, stable blocks of the Earth's crust that have survived the cycles of merging and splitting of continents over geological time. They typically consist of ancient crystalline rocks and form the core of continents.

Cratons are significant in geology because they provide insights into the early history of the Earth and the processes that formed the continents. Their stability is a result of having experienced a relatively low degree of tectonic activity over long periods compared to other geological features. This stability allows cratons to preserve ancient rocks and minerals, which can be critical for understanding the Earth's geological past.

The other options refer to different geological concepts: the Continental Shelf pertains to submerged land that extends from a continent's coastline, Oceanic Crust includes the dense and younger rocks forming the ocean floor, and the Asthenosphere is a semi-fluid layer beneath the lithosphere that plays a role in plate tectonics. These terms do not accurately denote the oldest and stable part of the upper mantle, which is why "Craton" is the correct choice.