Characterisation of local halo building blocks: Thamnos and Sequoia Emma Dodd, Tomás Ruiz-Lara, Amina Helmi, Carme Gallart, Thomas M. Callingham, Santi Cassisi, Emma Fernández-Alvar and Francisco Surot A&A, 698 (2025) A277 Published online: 20 June 2025 DOI: 10.1051/0004-6361/202451978