610:
storm wave base. The remarkably high content of analcime (30 volume percent) in some layers may be indicative of contemporaneous volcanic activity. Early diagenetic formation of analcime from volcanic glass in an alkaline environment has been described. High alkalinity of the lake water may also have been the reason for the almost complete lack of fossils in this part of the section. The overlying succession of sandstones, siltstones, stromatolites and emerged horizons reflects the upward shallowing of the formation. Besides extensive sand flats, large playas, several square kilometres in size, must have existed during the final stages of deposition. The playa deposits are represented by shaly sediments with intercalated feldspar-rich layers (2 to 4 centimetres (0.79 to 1.57 in)), stromatolite horizons (5 to 15 centimetres (2.0 to 5.9 in)) and fish scale bone beds (3 to 5 centimetres (1.2 to 2.0 in)). Fossiliferous stratiform carbonates (10 to 15 centimetres (3.9 to 5.9 in) thick) with molluscs of the
382:
393:
569:. In the lower half of this mainly pelitic succession, intercalations of dark brown, very often concretionary calcareous layers up to 1 metre (3.3 ft) thick, occur. These layers contain siltstone beds which locally exhibit flaser bedding, oscillation ripples and hummocky cross-bedding. The calcareous layers also contain small fossiliferous lenses with fishbones. The upper half of the basal shaly section contains a few layers, 10 to 20 centimetres (3.9 to 7.9 in) thick, which are whitish and
325:
630:
580:
The basal beds grade into a 20 metres (66 ft) thick succession of silty to fine-grained, and eventually medium- to coarse grained, sandstone. Sections of the uppermost part show various types of intercalations: silt- and sandstone layers grade laterally into sequences of interbedded shale and
553:
The Gai-As
Formation is the most widespread depositional unit within the Huab Basin. The approximately 70 metres (230 ft) thick succession is easily distinguished from all the other units by its characteristic reddish to violet color. The Gai-As Formation gradationally overlies the lacustrine
609:
The Gai-As
Formation as a whole displays an upward coarsening sequence which starts with distal shallow lacustrine shales. The occurrence of flaser bedding, oscillation ripples and hummocky cross-stratification in silty intercalations indicates that the sediment, surface must have been above the
558:
deposits of the Huab
Formation with a sharp contact. The basal beds of the formation are ubiquitously represented by fine-grained distal deposits and imply a much larger extent of the formation due to the absence of sediments from marginal environments.
1085:
The stratigraphy, sedimentology, and age of the Late
Palaeozoic Mesosaurus Inland Sea, SW-Gondwana - New implications from studies on sediments and altered pyroclastic layers of the Dwyka and Ecca Group (lower Karoo Supergroup) in southern Namibia (PhD
1116:
A. A. Warren, B. S. Rubidge, I. G. Stanistreet, H. Stollhofen, A. Wanke, E. M. Latimer, C. A. Marsicano and R. J. Damiani. 2001. Oldest Known
Stereospondylous Amphibian from the Early Permian of Namibia. Journal of Vertebrate Paleontology
730:. Due to increased subsidence in the central Paraná Basin, thicknesses of the correlative units are considerably greater than that of the Gai-As Formation, attaining a maximum of 1,200 metres (3,900 ft). In the
616:
type are transitional to the sand-flat facies which is characterised by sandy, flat and lenticular deposits and occasionally contain abundant root marks. The lowermost part of the formation indicates a
1113:
J. M. David, M. G. Simões, L. E. Anelli, R. Rohn, and F. Holzfoerster. 2011. Permian bivalves from the Gai-As
Formation, northern Namibia: systematics, taphonomy, and biostratigraphy. Alcheringa
511:
police station located at a spring in the central Huab area. The formation is a lithological unit with an approximate maximum thickness of 70 metres (230 ft), deposited in the
938:
Marsicano, C.A.; Pardo, J.D.; Smith, R.M.H.; Mancuso, A.M.; Gaetano, L.C.; Mocke, H. (2024). "Giant stem tetrapod was apex predator in
Gondwanan late Palaeozoic ice age".
597:
crystal moulds have been found locally. The white tuff layers within the Gai-As
Formation contain very well-preserved former glass shards, now mainly replaced by
759:
751:
707:
1083:
1190:
789:
711:
777:
1185:
755:
524:
146:
1059:
550:
beds in the Gai-As
Formation 14 metres (46 ft) above the stereospondyl find gave weighted mean values of 272 ± 1.8 Ma and 265 ± 2.5 Ma.
666:
512:
445:
340:
673:
1033:
1007:
680:
612:
355:
1130:
381:
921:
905:
855:
1205:
1200:
491:
correlation across present-day South
America, Africa, Antarctica and Australia. The Gai-As Formation has provided fossil
562:
The lower part of the succession is formed by approximately 50 metres (160 ft) of thick reddish-violet, slightly
523:, while later authors assign a separate formation to the upper 35 metres (115 ft) of the Gai-As Formation, named
1135:
1195:
273:
234:
1160:
1155:
1180:
1165:
227:
1034:"Depositional environments and stratigraphic correlation of the Karoo Sequence in northwestern Damaraland"
386:
Geologic map of Namibia with the Gai-As Formation partly cropping out in the northwestern area (orange)
1175:
471:
in southeastern Brazil, deposited in a larger basinal area, 150 million years before the break-up of
1093:
1068:
1170:
543:
593:. The shale frequently exhibits desiccation cracks, whereas root marks are abundant in sandstone.
508:
554:
deposits of the Huab Formation in the western part of the basin, but in the east succeeds the
114:
8:
799:
421:
1061:
Karoo-Etendeka Unconformities in NW Namibia and their Tectonic Implications (PhD thesis)
1140:
804:
794:
392:
1008:"Early Permian deposits of the Huab area Namibia: a continental to marine transition"
955:
723:
1150:
1145:
947:
715:
697:
468:
951:
653:
520:
516:
496:
449:
409:
266:
156:
142:
1124:
739:
719:
701:
464:
437:
433:
405:
312:
308:
288:
275:
249:
236:
71:
24:
444:. The Gai-As Formation represents the second-oldest sedimentary unit of the
959:
764:
747:
743:
735:
582:
477:
772:
that occur in the underlying Huab Formation are known from other parts of
519:, separated by a significant hiatus, and is unconformably overlain by the
925:
909:
859:
731:
46:
601:, are rich in potassium feldspar and have a porcelain-like appearance.
563:
540:
483:
457:
425:
220:
124:
91:
56:
463:
The Gai-As Formation is correlated with a series of formations in the
780:
of South Africa and coal deposits of the Lower Permian in Australia.
532:
528:
413:
183:
179:
96:
40:
28:
1006:
Holzförster, Frank; Stollhofen, Harald; Stanistreet, Ian G. (2000),
773:
590:
570:
536:
488:
487:
fossils in the underlying Huab Formation are characteristic of the
187:
86:
81:
66:
61:
51:
647:
629:
618:
586:
555:
492:
453:
441:
417:
330:
101:
76:
32:
1005:
727:
598:
594:
589:, bone beds of fish scales and white layers rich in authigenic
472:
428:
and designated "Ecca" Group, because it does not belong to the
205:
637:
The following fossils have been reported from the formation:
574:
566:
429:
201:
546:. U/Pb SHRIMP dating of zircons from two of several fallout
1031:
547:
197:
937:
706:
The lower part of the formation is correlated with the
971:
969:
1032:
Horsthemke, E.; Ledendecker, S.; Porada, H. (1990),
874:
872:
870:
868:
790:
List of fossiliferous stratigraphic units in Namibia
890:
507:The Gai-As Formation is named after the ruins of a
1041:Communications of the Geological Survey of Namibia
1015:Communications of the Geological Survey of Namibia
987:
978:
966:
865:
837:
1122:
922:Klein Gai-As, upper Gai-As Formation, Huab Basin
906:Klein Gai-As, lower Gai-As Formation, Huab Basin
830:
828:
881:
367:Stanistreet & Stollhofen 1999 (redefined)
825:
816:
750:, the formation is time-equivalent with the
581:sandstone with occasional intercalations of
573:-rich and occasionally thin layers of green
1191:Fossiliferous stratigraphic units of Africa
899:
604:
380:
1186:Permian southern paleotemperate deposits
931:
628:
391:
1094:Julius-Maximilians-Universität Würzburg
1069:Julius-Maximilians-Universität Würzburg
1123:
1081:
1057:
851:
849:
633:Reconstruction of a stereospondylid
452:. The formation was deposited in a
13:
1107:
915:
846:
14:
1217:
624:
585:layers, carbonate horizons with
323:
44:
999:
691:
1131:Geologic formations of Namibia
896:Holzförster et al, 2000, p.286
502:
1:
856:Huab Basin amphibian locality
810:
993:Horsthemke et al, 1990, p.69
984:Horsthemke et al, 1990, p.75
975:Horsthemke et al, 1990, p.74
878:Horsthemke et al, 1990, p.73
843:Horsthemke et al, 1990, p.68
762:. The fossil assemblages of
734:of southern Namibia and the
710:and the upper part with the
267:Approximate paleocoordinates
7:
783:
10:
1222:
1206:Geography of Kunene Region
1201:Geography of Erongo Region
952:10.1038/s41586-024-07572-0
695:
527:. The formation comprises
365:Horsthemke 1992 (original)
621:-lacustrine environment.
379:
371:
361:
351:
346:
336:
318:
304:
265:
226:
216:
211:
193:
175:
170:
162:
152:
138:
130:
120:
110:
23:
18:
1136:Permian System of Africa
605:Depositional environment
1196:Paleontology in Namibia
166:70 m (230 ft)
1082:Werner, Mario (2006),
1058:Wanke, Angsar (2000),
634:
515:where it overlies the
432:, in the southwestern
397:
396:Early Permian (280 Ma)
760:Fort Brown Formations
681:Terraia cf. altissima
654:Stereospondyli indet.
632:
495:and an indeterminate
395:
1161:Siltstone formations
1156:Sandstone formations
708:Serra Alta Formation
424:correlated with the
115:Geological formation
1181:Lacustrine deposits
1166:Mudstone formations
800:Ganigobis Formation
674:Huabiella compressa
475:. The abundance of
285: /
246: /
25:Stratigraphic range
887:Werner, 2006, p.14
805:Gondwanide orogeny
795:Geology of Namibia
712:Teresina Formation
667:Cowperesia emerita
635:
398:
946:(8021): 577–582.
834:Wanke, 2000, p.25
822:Wanke, 2000, p.11
778:Vryheid Formation
724:Rio Grande do Sul
613:Terraia altissima
390:
389:
1213:
1176:Fluvial deposits
1103:
1102:
1101:
1096:, pp. 1–428
1091:
1078:
1077:
1076:
1071:, pp. 1–114
1066:
1054:
1053:
1052:
1038:
1028:
1027:
1026:
1012:
994:
991:
985:
982:
976:
973:
964:
963:
935:
929:
919:
913:
903:
897:
894:
888:
885:
879:
876:
863:
853:
844:
841:
835:
832:
823:
820:
448:, overlying the
440:of northwestern
402:Gai-As Formation
384:
329:
327:
326:
300:
299:
297:
296:
295:
290:
286:
283:
282:
281:
278:
261:
260:
258:
257:
256:
251:
247:
244:
243:
242:
239:
106:
43:
19:Gai-As Formation
16:
15:
1221:
1220:
1216:
1215:
1214:
1212:
1211:
1210:
1171:Tuff formations
1121:
1120:
1110:
1108:Further reading
1099:
1097:
1089:
1074:
1072:
1064:
1050:
1048:
1036:
1024:
1022:
1010:
1002:
997:
992:
988:
983:
979:
974:
967:
936:
932:
920:
916:
904:
900:
895:
891:
886:
882:
877:
866:
854:
847:
842:
838:
833:
826:
821:
817:
813:
786:
704:
694:
648:Gaiasia jennyae
627:
607:
539:deposited in a
525:Doros Formation
509:colonial German
505:
497:stereospondylid
385:
366:
324:
322:
293:
291:
287:
284:
279:
276:
274:
272:
271:
254:
252:
248:
245:
240:
237:
235:
233:
232:
147:Doros Formation
105:
104:
99:
94:
89:
84:
79:
74:
69:
64:
59:
54:
49:
38:
37:
35:
12:
11:
5:
1219:
1209:
1208:
1203:
1198:
1193:
1188:
1183:
1178:
1173:
1168:
1163:
1158:
1153:
1148:
1143:
1138:
1133:
1119:
1118:
1114:
1109:
1106:
1105:
1104:
1079:
1055:
1029:
1001:
998:
996:
995:
986:
977:
965:
930:
914:
898:
889:
880:
864:
845:
836:
824:
814:
812:
809:
808:
807:
802:
797:
792:
785:
782:
720:Pelotas Basins
693:
690:
689:
688:
686:T. cf. curvata
677:
670:
662:
661:
657:
656:
651:
643:
642:
626:
625:Fossil content
623:
606:
603:
521:Etjo Sandstone
517:Huab Formation
504:
501:
450:Huab Formation
410:Middle Permian
388:
387:
377:
376:
373:
369:
368:
363:
359:
358:
353:
349:
348:
344:
343:
338:
334:
333:
320:
316:
315:
313:Erongo Regions
306:
302:
301:
269:
263:
262:
230:
224:
223:
218:
214:
213:
209:
208:
195:
191:
190:
177:
173:
172:
168:
167:
164:
160:
159:
157:Huab Formation
154:
150:
149:
143:Etjo Sandstone
140:
136:
135:
132:
128:
127:
122:
118:
117:
112:
108:
107:
100:
95:
90:
85:
80:
75:
70:
65:
60:
55:
50:
45:
21:
20:
9:
6:
4:
3:
2:
1218:
1207:
1204:
1202:
1199:
1197:
1194:
1192:
1189:
1187:
1184:
1182:
1179:
1177:
1174:
1172:
1169:
1167:
1164:
1162:
1159:
1157:
1154:
1152:
1149:
1147:
1144:
1142:
1139:
1137:
1134:
1132:
1129:
1128:
1126:
1115:
1112:
1111:
1095:
1088:
1087:
1080:
1070:
1063:
1062:
1056:
1046:
1042:
1035:
1030:
1020:
1016:
1009:
1004:
1003:
990:
981:
972:
970:
961:
957:
953:
949:
945:
941:
934:
927:
923:
918:
911:
907:
902:
893:
884:
875:
873:
871:
869:
861:
857:
852:
850:
840:
831:
829:
819:
815:
806:
803:
801:
798:
796:
793:
791:
788:
787:
781:
779:
775:
771:
767:
766:
761:
757:
753:
749:
745:
741:
737:
733:
729:
725:
721:
717:
713:
709:
703:
702:Pelotas Basin
699:
687:
683:
682:
678:
676:
675:
671:
669:
668:
664:
663:
659:
658:
655:
652:
650:
649:
645:
644:
640:
639:
638:
631:
622:
620:
615:
614:
602:
600:
596:
592:
588:
584:
583:stromatolitic
578:
576:
572:
568:
565:
560:
557:
551:
549:
545:
542:
538:
534:
530:
526:
522:
518:
514:
510:
500:
498:
494:
490:
486:
485:
480:
479:
474:
470:
469:Paraná Basins
466:
461:
459:
455:
451:
447:
443:
439:
438:Erongo Region
436:and northern
435:
434:Kunene Region
431:
427:
423:
419:
415:
411:
407:
403:
394:
383:
378:
374:
370:
364:
360:
357:
354:
350:
345:
342:
339:
335:
332:
321:
317:
314:
310:
307:
303:
298:
289:49.1°S 22.6°W
270:
268:
264:
259:
250:20.8°S 14.1°E
231:
229:
225:
222:
219:
215:
210:
207:
203:
199:
196:
192:
189:
185:
181:
178:
174:
169:
165:
161:
158:
155:
151:
148:
144:
141:
137:
133:
129:
126:
123:
119:
116:
113:
109:
103:
98:
93:
88:
83:
78:
73:
68:
63:
58:
53:
48:
42:
39:272–265
34:
30:
26:
22:
17:
1098:, retrieved
1084:
1073:, retrieved
1060:
1049:, retrieved
1044:
1040:
1023:, retrieved
1018:
1014:
1000:Bibliography
989:
980:
943:
939:
933:
917:
901:
892:
883:
839:
818:
769:
765:Glossopteris
763:
748:South Africa
744:Western Cape
705:
698:Paraná Basin
692:Correlations
685:
679:
672:
665:
646:
636:
611:
608:
579:
561:
552:
506:
482:
478:Glossopteris
476:
462:
401:
399:
347:Type section
294:-49.1; -22.6
134:Upper, lower
125:"Ecca" Group
1117:21(1):34-39
926:Fossilworks
910:Fossilworks
860:Fossilworks
732:Karoo Basin
544:environment
503:Description
420:) geologic
292: /
255:-20.8; 14.1
253: /
228:Coordinates
1125:Categories
1100:2018-08-26
1075:2018-08-26
1051:2018-08-26
1025:2018-08-26
811:References
770:Mesosaurus
752:Collingham
696:See also:
641:Amphibians
564:calcareous
541:lacustrine
533:siltstones
529:sandstones
513:Huab Basin
484:Mesosaurus
458:lacustrine
446:Huab Basin
426:Ecca Group
341:Huab Basin
221:Damaraland
1141:Kungurian
1021:: 247–257
537:mudstones
489:Gondwanan
460:setting.
422:formation
414:Kungurian
352:Named for
184:siltstone
180:Sandstone
171:Lithology
163:Thickness
139:Underlies
131:Sub-units
29:Kungurian
960:38961286
784:See also
774:Gondwana
740:Northern
660:Bivalves
591:feldspar
587:molluscs
571:analcime
493:bivalves
372:Location
362:Named by
217:Location
212:Location
188:mudstone
153:Overlies
1151:Wordian
1146:Roadian
1086:thesis)
1047:: 67–77
736:Eastern
714:of the
556:fluvial
465:Pelotas
454:fluvial
442:Namibia
418:Wordian
331:Namibia
319:Country
280:22°36′W
277:49°06′S
241:14°06′E
238:20°48′S
176:Primary
121:Unit of
33:Wordian
958:
940:Nature
776:; the
728:Brazil
716:Paraná
619:fluvio
599:barite
595:Halite
567:shales
473:Pangea
404:is an
375:Gai-As
356:Gai-As
337:Extent
328:
311:&
309:Kunene
305:Region
206:halite
1090:(PDF)
1065:(PDF)
1037:(PDF)
1011:(PDF)
756:Ripon
575:chert
430:Karoo
406:Early
202:chert
194:Other
956:PMID
928:.org
912:.org
862:.org
768:and
758:and
742:and
718:and
700:and
548:tuff
535:and
481:and
467:and
400:The
198:Tuff
111:Type
47:Preęž’
948:doi
944:631
924:at
908:at
858:at
722:in
456:to
416:to
408:to
145:or
1127::
1092:,
1067:,
1043:,
1039:,
1019:12
1017:,
1013:,
968:^
954:.
942:.
867:^
848:^
827:^
754:,
746:,
738:,
726:,
684:,
577:.
531:,
499:.
204:,
200:,
186:,
182:,
97:Pg
41:Ma
27::
1045:6
962:.
950::
412:(
102:N
92:K
87:J
82:T
77:P
72:C
67:D
62:S
57:O
52:ęž’
36:~
31:-
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