当前位置: X-MOL 学术J. South Am. Earth Sci. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Slab flattening and tractional coupling drove Neogene clockwise rotation of Chiapas Massif, Mexico: Paleomagnetism of the Eocene El Bosque Formation
Journal of South American Earth Sciences ( IF 1.8 ) Pub Date : 2020-12-01 , DOI: 10.1016/j.jsames.2020.102932
Roberto S. Molina-Garza , James Pindell , Paola Catalina Montaño Cortés

Abstract Dual-polarity characteristic magnetizations in red sandstones of the Early and Middle Eocene El Bosque Formation in central Chiapas, Mexico (D = 9.3° I = 23.6°; N = 19 selected sites, k = 32.6, α95 = 6.0°) indicate about 20° of clockwise rotation when compared with a coeval paleomagnetic reference pole in the North America craton. We interpret the rotation to result from traction between the base of the Chiapas Massif lithosphere and the low-angle subducting Cocos Plate. The northwest end of the massif overlies a shallower portion of the Cocos plate interface than the southeast end, which implies a greater amount and longer period of tractional coupling between the two plates in the northwest. We judge that the downdip, steep limb of the Cocos slab (beneath Gulf of Mexico) lies roughly in the regional mantle or hotspot reference frame. Assessments of Neogene North America-hotspot relative motion indicate an azimuth of ENE-WSW at 20 mm/yr, and thus we envisage that (1) the flat slab zone has been caused by the WSW telescoping of North America across the former geometry of the Cocos Benioff Zone, and (2) that the WNW end of the massif has undergone most tractional coupling with Cocos Plate than the ESE end. In turn, because the massif appears to have behaved as a rigid, unbroken body, this greater coupling has induced clockwise rotation that has been transferred as near-field shortening into the adjacent Sierra de Chiapas foldbelt.

中文翻译:

板片压扁和牵引耦合驱动墨西哥恰帕斯地块的新近纪顺时针旋转:始新世 El Bosque 地层的古地磁

摘要 墨西哥恰帕斯州中部早中始新世 El Bosque 组红砂岩的双极性特征磁化强度(D = 9.3° I = 23.6°;N = 19 个选定地点,k = 32.6,α95 = 6.0°)表明大约与北美克拉通同期古地磁参考极相比,顺时针旋转 20°。我们将旋转解释为恰帕斯地块岩石圈底部和低角度俯冲科科斯板块之间的牵引力。地块的西北端覆盖在比东南端更浅的 Cocos 板块界面上,这意味着西北两个板块之间的牵引耦合量更大,周期更长。我们判断 Cocos 板块(墨西哥湾下方)的下倾、陡峭的边缘大致位于区域地幔或热点参考系中。对新近纪北美热点相对运动的评估表明 ENE-WSW 的方位角为 20 毫米/年,因此我们设想 (1) 平板带是由北美的 WSW 伸缩穿过以前的几何形状造成的Cocos Benioff Zone,以及 (2) 地块的 WNW 端比 ESE 端与 Cocos Plate 发生了最大的牵引耦合。反过来,由于地块似乎表现得像一个刚性的、完整的物体,这种更大的耦合引起了顺时针旋转,这种旋转已作为近场缩短转移到相邻的 Sierra de Chiapas 褶皱带中。因此我们设想 (1) 平板带是由北美 WSW 伸缩穿过 Cocos Benioff 带的前几何形状造成的,并且 (2) 地块的 WNW 端与 Cocos 发生了最大的牵引耦合盘比ESE端。反过来,由于地块似乎表现得像一个刚性的、完整的物体,这种更大的耦合引起了顺时针旋转,这种旋转已作为近场缩短转移到相邻的 Sierra de Chiapas 褶皱带中。因此我们设想 (1) 平板区是由北美 WSW 伸缩穿过 Cocos Benioff 区的前几何形状造成的,以及 (2) 地块的 WNW 端与 Cocos 发生了最大的牵引耦合盘比ESE端。反过来,由于地块似乎表现得像一个刚性的、完整的物体,这种更大的耦合引起了顺时针旋转,这种旋转已作为近场缩短转移到相邻的 Sierra de Chiapas 褶皱带中。
更新日期:2020-12-01
down
wechat
bug