pour les déterminations je conseille : https://l.facebook.com/l.php?u=https%3A%2F%2Farchive.org%2Fdetails%2Fbulletinofbritis15brit%2Fpage%2F46%2Fmode%2F2up%3Fview%3Dtheater&h=AT2hHENfMS4mQKlBO95wwBKNTOaJmGUdLP6hW9AOmdmt8TTXLVT_d2cxnGO1kwHj1Q87BWkM4PniMYJwx9O4Wuj4kNC0k1F96iXrnvkfRF_iiU2lMcSXBusakcUM3i2LClw&__tn__=H-R&c[0]=AT3GAYUZi-Z5HHQR1PV0B8SCA_Hcj3tCWfC4fP0KrFnP-MMmXjVQFldWPQnENBF_uKUWluFN3h2Yy8Gyd5KmqslVXOMUlquPFtFTXb_hOuxtshDFKQlmEdf9Mz47KaEmIEsOBLOo8Tu9iAOn0Nz_bZVZuDByWGVF7A1cBvGFQVo2ybEsSUWJHd8AcaijSmDNpY7PTspL-NQXkaYshI5ZgJvlBhF3nthBdw
ou références sur page Facebook "patrimoine géologique Hauts de France"