What did de vaca and de Cardenas write

They wrote exploration narratives.

Explanation:

Cabeza de vaca and Lopez de Cardenas were Spanish explorers who wrote first hand exploration narrative of their expedition in America.

Exploration narratives are those narratives or account that records a travellers firsthand experience of his travellings.

Alvar Nunez Cabeza de Vaca wrote about his exploration in America entitled 'A Journey through Texas.' The narrative of de vaca records his experience as captive on an island in the Gulf of Mexico.

Garcia Lopez de Cadenas wrote about his exploration under the title 'Boulders taller than the Great Tower of Seville.' de Cardenas's exploration narrative records his search for the Seven Cities of Cibola that were believed to be made of gold. de Cadenas was the first white man to view the Colorado river from the Grand Canyon's edge.

So, they both wrote exploration narratives.